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Synthesis of amides
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(2-(Thiophen-2-ylmethyl)phenyl)boronic acid is a a highly active catalyst for
direct amidation between carboxylic acids and amines at room temperature for a
large range of substrates. Slightly higher temperatures are required for
challenging starting materials. Aliphatic, α-hydroxyl, aromatic, and
heteroaromatic acids as well as primary, secondary, heterocyclic, and even
functionalized amines can be used.
T. M. El Dine, W. Erb, Y. Berhault, J. Rouden, J. Blanchet, J. Org. Chem.,
2015,
80, 4532-4544.
A commercially available thianthrene boron acid catalyzes a versatile
dehydrative amidation. The catalyst shows high catalytic activity to both
aliphatic and less reactive aromatic carboxylic acid substrates, including
several bioactive or clinical molecules with a carboxylic acid group.
B. Pan, D.-M. Huang, H.-T. Sun, S.-N. Song, X.-B. Sun, J. Org. Chem., 2023, 88,
2832-2840.
5-methoxy-2-iodophenylboronic acid (MIBA) is kinetically very active in a
catalytic, direct amidation employing free carboxylic acids and amines providing
high yields of amide products in short reaction times under mild conditions at
ambient temperature in the presence of molecular sieves. A possible catalytic
cycle is based on the presumed formation of an acylborate intermediate.
N. Gernigon, R. M. Al-Zoubi, D. G. Hall, J. Org. Chem., 2012,
77, 8386-8400.
Stable and easily accessible triflylpyridinium reagents mediate an effective
synthesis of a broad range of amides and esters at ambient temperature within 5
min. In addition, a flow process enables a scalable synthesis of peptides and
esters. Moreover, excellent chirality retentions are presented during activation
of carboxylic acid.
D. Chen, L. Xu, B. Ren, Z. Wang, C. Liu, Org. Lett., 2023, 25,
4571-4575.
Ammonia-borane serves as an efficient precatalyst for the direct amidation of
both aromatic and aliphatic carboxylic acids. This method is efficient with
equimolar amounts of the coupling partners and offers high functional group
tolerance and chromatography-free purification.
P. V. Ramachandran, H. J. Hamann, Org. Lett., 2021, 23,
2938-2942.
Tetramethyl orthosilicate (TMOS) is an effective reagent for direct amidation of
aliphatic and aromatic carboxylic acids with amines and anilines in very good
yields. The amide products are obtained in pure form directly after workup
without the need for any further purification. A silyl ester as the putative
activated intermediate is observed by NMR methods.
D. C. Braddock, P. D. Lickiss, B. C. Rowley, D. Pugh, T. Purnomo, G. Santhakumar,
S. J. Fussell, Org. Lett.,
2018, 20, 950-953.
Triphenylphosphine oxide catalyzes amidation and esterification for an
efficient synthesis of dipeptides, amides, and esters in good yields in less
than 10 m without racemization. This reaction is applicable to challenging
couplings of hindered carboxylic acids with weak nucleophiles amines or
alcohols.
J.-W. Ren, M.-N. Tong, Y.-F. Zhao, F. Ni, Org. Lett., 2021, 23,
7497-7502.
The combination of trimethylacetic anhydride and catalytic amounts of
potassium tert-butoxide mediates an amination of carboxylic acids with
DMF as a dimethylamine reagent to provide N,N-dimethylamides. The
applicability of this protocol is demonstrated by late-stage dimethylamidations
of complex drug molecules.
Y. Huang, J. Zhang, Synthesis, 2022, 54,
3595-3604.
Borane-trimethylamine is an efficient reducing agent for the selective
methylation and formylation of amines with 1 atm CO2 under metal-free
conditions. 6-Amino-2-picoline serves as a highly efficient catalyst for the
methylation of various secondary amines, whereas in its absence, the formylation
of primary and secondary amines was achieved in high yield with high
chemoselectivity.
Y. Zhang, H. Zhang, K. Gao, Org. Lett., 2021, 23,
8282-8286.
An efficient decarboxylative N-formylation of amines with glyoxylic
acid provides formamides in good yields. The reaction tolerates a wide range of
functional groups under metal free and base free conditions. In addition,
large-scale experiments and high chemoselectivity have shown great potential
application of this strategy.
J. Wu, Y. Zhang, J. Yang, L. Yu, S. Zhang, J. Zhou, Z. Li, X. Xu, H. Xu, J. Org. Chem., 2023, 88,
13590-13597.
Ball milling of aromatic, heteroaromatic, vinylic, and aliphatic esters with
ethanol and calcium nitride provides the corresponding primary amides in good
yields. The transformation is compatible with a variety of functional groups and
maintained the integrity of a stereocenter α to carbonyl.
J. Gómez-Carpintero, J. D. Sánchez, J. F. González, J. C. Menéndez, J. Org. Chem., 2021, 86,
14232-14237.
Reactions of tert-butyl esters with α,α-dichlorodiphenylmethane as the
chlorinating agent and SnCl2 as catalyst generate acid chloride
intermediates in situ, that were subsequently used in reactions with a variety
of alcohols and amines to afford the corresponding esters and amides in high
yields under mild reaction conditions.
V. H. Tran, A. T. Nguyen, H.-K. Kim, J. Org. Chem., 2023, 88,
13291-13302.
The L-proline-based amphiphile PS-750-M enables extremely fast
amide couplings in water mediated by 1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide (without
hydroxybenzotriazole). Product precipitation and isolation by
filtration completely avoids the use of organic solvent. This methodology avoids product epimerization
and is
scalable.
S. Sharma, N. W. Buchbinder, W. M. Braje, S. Handa,
Org. Lett., 2020, 22, 5737-5740.
A simple and metal-free method for the direct formation of dialkylamides from
carboxylic acids employs N,N-dialkylformamides as amine source. The
one-pot reaction is promoted by propylphosphonic anhydride (T3P®) in the
presence of 0.5 equivalents of HCl.
L. Bannwart, S. Abele, S. Tortoioli,
Synthesis, 2016, 48, 2069-2078.
NDTP is an unprecedented mild, nonirritating, conveniently available, and
recyclable coupling reagent, which activates carboxylic acids via acyl
thiocyanide and enables a rapid amide and peptide synthesis at very mild
conditions. In addition, the methodology is compatible with Fmoc-SPPS.
Y. Li, J. Li, G. Bao, C. Yu, Y. Liu, Z. He, P. Wang, W. Ma, J. Xie, W. Sun,
R. Wang, Org. Lett.,
2022, 24, 1169-1174.
A palladium-catalyzed N-acylation of tertiary amines by carboxylic
acids produces the corresponding amides in very good yields via cleavage of a
C-N bond. Both aromatic and aliphatic acids served well as the acylating
reagents.
Z. Li, L. Liu, K. Xu, T. Huang, X. Li, B. Song, T. Chen,
Org. Lett., 2020, 22, 5517-5521.
Amides were produced from carboxylic acids and amines in the presence of
XtalFluor-E as an activator. Optically active amines and/or carboxylic acids
were not epimerized/racemized during the process and even poorly reactive
carboxylic acids can be transformed to amides.
A. Orliac, D. G. Pardo, A. Bombrun, J. Cossy, Org. Lett., 2013,
15, 902-905.
The reaction of amine-boranes as dual-purpose reagents with
aliphatic and aromatic carboxylic acids provides amides in very good yields. Delivery of gaseous or
low-boiling amines as their borane complexes provides a major advantage over
existing methodologies.
P. V. Ramachandran, H. J. Hamann, S. Choudhary,
Org. Lett., 2020, 22, 8593-8597.
A highly reactive ynamine, generated in situ by UV irradiation of an
aminocyclopropenone, mediates dehydration condensations of carboxylic acids and
amines to provide amides. This reaction is completely controllable by the ON/OFF
states of a UV lamp.
K. Mishiro, Y. Yushima, M. Kunishima, Org. Lett.,
2017, 19, 4912-4915.
Ynamides as novel coupling reagents enable a highly efficient, two-step, one-pot
synthetic strategy for amides and peptides under extremely mild reaction
conditions. Importantly, no racemization was detected during the activation of
chiral carboxylic acids. Excellent amidation selectivity toward amino groups in
the presence of -OH, -SH, -CONH2, ArNH2, and the NH of
indole was observed.
L. Hu, S. Xu, Z. Zhao, Y. Yang, Z. Peng, M. Yang, C. Wang, J. Zhao, J. Am. Chem. Soc., 2016,
138, 13135-13138.
An effective protocol for a waste-minimized, environmentally benign thermal
condensation of carboxylic acids with amines has been identified. Fourteen
examples demonstrate the applicability of this procedure to aliphatic, aromatic
and heteroaromatic carboxylic acids and primary and secondary aliphatic as well
as aromatic amines. The approach leads to the corresponding amides in good
yields.
L. J. Gooßen, D. M. Ohlmann, P. P. Lange, Synthesis, 2009,
160-164.
Nanosized sulfated titania was prepared by a sol-gel hydrothermal process. The
nanoparticles showed high catalytic activity in a direct amidation of fatty
acids as well as benzoic acids with various amines under solvent-free conditions.
M. Hosseini-Sarvari, E. Sodagar, M. M. Doroodmand, J. Org. Chem., 2011,
76, 2853-2859.
The mild combination of T3P (n-propanephosphonic acid anhydride) and
pyridine enables a low-epimerization amide bond formation. This robust and
practical method is general for the coupling of various racemization-prone acid
substrates and amines, including relatively non-nucleophilic anilines, and
provides amides in high yields with very low epimerization.
J. R. Dunetz, Y. Xiang, A. Baldwin, J. Ringling, Org. Lett., 2011,
13, 5048-5051.
A broadly applicable method for amide C-N and ester C-O bond formation is
based on formylpyrrolidine (FPyr) as a Lewis base catalyst and trichlorotriazine
(TCT) as a cost-efficient reagent for OH-group activation. The new approach is
distinguished by excellent cost-efficiency, waste-balance, scalability, and high
levels of functional group compatibility.
P. H. Huy, C. Mbouhom, J. Org. Chem., 2019, 84,
7399-7406.
Use of uronium salt
(1-cyano-2-ethoxy-2-oxoethylidenaminooxy)dimethylaminomorpholinocarbenium
hexafluorophosphate (COMU) as a coupling reagent, 2,6-lutidine, and TPGS-750-M
enables a general, mild, and environmentally responsible method for the
formation of amide/peptide bonds in an aqueous micellar medium. The
aqueous reaction medium is recyclable leading to low E Factors.
C. M. Gabriel, M. Keener, F. Gallou, B. H. Lipshutz, Org. Lett.,
2015,
17, 3968-3971.
The coupling reagent ethyl 2-cyano-2-(2-nitrobenzenesulfonyloxyimino)acetate (o-NosylOXY)
produces only byproducts that can be easily recovered and reused for the
synthesis of the same reagent, making coupling reactions to yield amides,
hydroxamates, peptides, and esters more environmentally friendly and
cost-effective.
D. Dev, N. B. Palakurthy, K. Thalluri, J. Chandra, B. Mandal, J. Org. Chem., 2014,
79, 5420-5431.
An efficient amidation of carboxylate salts with either free amines or their
ammonium hydrochloride salts can be achieved in very good yields using HBTU in
combination with Hünig’s base in 1-2 h. The protocol is valuable for the
coupling of carboxylates for which the corresponding carboxylic acids or acyl
chlorides are unstable. Addition of carbon dioxide to a lithiated terminal
alkyne enables the synthesis of acetylenic amides in one pot.
J. D. Goodreid, P. A. Duspara, C. Bosch, R. A. Batey, J. Org. Chem., 2014,
79, 943-954.
A manganese(I)-catalyzed reaction of a wide range of aromatic, aliphatic, and
heterocyclic esters, even fatty acid esters with a diverse range of primary aryl
amines, primary alkyl amines, and secondary alkyl amines provides amides in good
yields.
Z. Fu, X. Wang, S. Tao, Q. Bu, D. Wei, N. Liu, J. Org. Chem., 2021, 86,
2339-2358.
Readily available N-acylbenzotriazoles efficiently acylate aqueous
ammonia and primary and secondary amines to give primary, secondary, and
tertiary amides in very good yields.
A. R. Katritzky, H.-Y. He, K. Suzuki, J. Org. Chem., 2000,
65, 8210-8213.
Readily available N-acylbenzotriazoles efficiently acylate aqueous
ammonia and primary and secondary amines to give primary, secondary, and
tertiary amides in very good yields.
A. R. Katritzky, H.-Y. He, K. Suzuki, J. Org. Chem., 2000,
65, 8210-8213.
An amide formation using primary amines and potassium acyltrifluoroborates, that
proceeds rapidly in water, is promoted by simple chlorinating agents. The
reaction is fast at acidic pH and tolerates alcohols, carboxylic acids, and even
secondary amines in the substrates. It is applicable to the (late-stage)
functionalization of primary amides, sulfonamides, and other N-functional
groups that typically resist classical acylations.
A. O. Gálvez, C. P. Schaack, H. Noda, J. W. Bode, J. Am. Chem. Soc., 2017,
139, 1826-1829.
Tetrakis(dimethylamido)diboron and tetrahydroxydiboron catalyze a simple and
highly efficient condensation of aromatic carboxylic acids with amines to
provide aryl amides. This catalytic approach avoids the use of stoichiometric or
additional dehydrating agents.
D. N. Sawant, D. B. Bagal, S. Ogawa, K. Selvam, S. Saito, Org. Lett.,
2018, 20, 4397-4400.
A degradable 1,3,5-triazo-2,4,6-triphosphorine (TAP) motif enables a
dehydrative formation of amide bonds between diverse combinations of aromatic
carboxylic acids and amines. The underlying reaction mechanism was investigated,
and potential catalyst intermediates were characterized.
. S. Movahed, D. N. Sawant, D. B. Bagal, S. Saito, Synthesis, 2020, 52,
3253-3262.
An electrochemical amidation of benzoyl hydrazine/carbazate and primary/secondary
amine as coupling partners proceeds under metal-free and exogenous oxidant-free
conditions produces only N2 and H2 as byproducts.
Mechanistic studies reveal the in situ generations of both acyl and N-centered
radicals.
T. Alam, A. Rakshit, H. N. Dhara, A. Palai, B. K. Patel, Org. Lett.,
2022, 24, 6619-6624.
A mild method for N-acylation of primary and secondary amines with
α-diketones in high yield is induced by ultraviolet (UV) light at room
temperature. This system can also be applied to the synthesis of several amino
acid derivatives. Mechanistic studies show that benzoin is generated in situ
from benzil under UV irradiation.
Z. Xu, T. Yang, N. Tang, Y. Ou, S.-F. Yin, N. Kambe, R. Qiu, Org. Lett., 2021, 23,
5329-5333.
Ynoates as novel coupling reagents enable a highly efficient and simple protocol
for the direct amidation of carboxylic acids in very good yields via in situ
α-acyl enol ester intermediates formation under mild reaction conditions.
X. Xu, H. Feng, L. Huang, X. Liu, J. Org. Chem., 2018, 83,
7962-7969.
Electrophilic activation of carboxylic anhydride using methanesulfonyl chloride
is an efficient method for nucleophilic acylation, which increases product yield
by restricting the formation of corresponding acid as a side product. The
developed protocol enables one-pot nucleophilic acylation of anhydrides with
several types of N- and S-nucleophiles in high yield demonstrating appreciable
functional group tolerance.
V. Kumar, A. Rana, C. L. Meena, N. Sharma, Y. Kumar, D. Mehajan, Synthesis, 2018, 50,
3902-3910.
A chromium-catalyzed activation of acyl C-O bonds with magnesium enables an
amidation of esters with nitroarenes in the presence of chlorotrimethylsilane as
additive. The reaction provides a step-economic strategy to the synthesis of
important amide motifs using inexpensive and air-stable nitroarenes as amino
sources.
L. Ling, C. Chen, M. Luo, X. Zeng,
Org. Lett., 2019, 21, 1912-1916.
B2(OH)4 mediates a reductive transamidation reaction
between N-acyl benzotriazoles and organic nitro compounds or NaNO2
under mild conditions in H2O as solvent. N-Deuterated amides
can be synthesized when conducting the reaction in D2O. A reasonable
reaction mechanism involves bond metathesis between the AcBt amide and an amino
boric acid intermediate.
J. Bai, S. Li, R. Zhu, Y. Li, W. Li, J. Org. Chem., 2023, 88,
3714-3723.
An organic photoredox catalyst promotes a metal-, base-, and additive-free
amide bond formation reaction in high yields. This green approach offers a broad
substrate scope, good compatibility with water and air, and tolerates functional
groups such as alcohols, phenols, ethers, esters, halogens, or heterocycles.
W. Song, K. Dong, M. Li,
Org. Lett., 2020, 22, 371-375.
A method for N-(hetero)arylamide synthesis based on rarely explored
amine activation, rather than classical acid activation, shows a broad scope including challenging
amides. The
activated amines are easily prepared using a three-component reaction with
commercial reagents.
Y.-P. Zhu, S. Sergeyev, P. Franck, R. V. A. Orru, B. U. W. Maes, Org. Lett.,
2016, 18, 4602-4605.
The use of sulfinylamides generated in situ by the reaction of pure amines with
prop-2-ene-1-sulfinyl chloride enables an efficient amidification of carboxylic
acids. The method allows the conversion of aliphatic acids, including pivalic
acid, aromatic acids, and primary and secondary amines and tolerates acids
bearing unprotected alcohol, phenol, and ketone moieties without α-epimerization.
J. Bai, B. K. Zembrón, P. Vogel, Org. Lett., 2014,
16, 604-607.
The combination of dichloro(methyl)(3,3,3-trifluoropropyl)silane (MTFPSCl2)
and imidazole mediates an amidation of amino acids. MTFPSCl2
activates the carboxy group and protects the α-amino group of amino acids. The
corresponding amino acid amides were synthesized in good yields without
racemization.
T. Nobuta, H. Morishita, Y. Suto, N. Yamagiwa, Synlett, 2022,
33,
1563-1569.
HSi[OCH(CF3)2]3 catalyzes a reliable
protocol for peptide bond formation in high yield that is generally applicable
to natural and unnatural α-amino acids, β-amino acids, and peptides bearing
various functional groups. This method facilitates the sustainable utilization
of natural resources by using a catalyst and an auxiliary based on
earth-abundant silicon.
W. Muramatsu, H. Yamamoto, Org. Lett.,
2022, 24, 7194-7199.
Imidazolylsilanes are highly useful coupling reagents for peptide synthesis
from N-,C-terminal unprotected amino acids with amino acid tert-butyl
esters. An optional deprotection of the tert-butyl ester at the C-terminus and
cyclization sequentially proceed to afford silacyclic dipeptides, that can
act as both nucleophiles and electrophiles for further peptide elongation.
T. Hattori, H. Yamamoto, J. Am. Chem. Soc.,
2022, 144, 1758-1765.
Thionyl fluoride (SOF2) is a powerful reagent for both the rapid
syntheses of acyl fluorides and for one-pot syntheses of amides, peptides,
esters, and thioesters. In addition, thionyl fluoride-mediated one-pot reactions
can be extended beyond nucleophilic acyl substitutions to mild reductions of
carboxylic acids using NaBH4.
T. G. Bolduc, C. Lee, W. P. Chappell, G. M. Sammis, J. Org. Chem., 2022, 87,
7308-7318.
The use two different silylating reagents (HSi[OCH(CF3)2]3,
MTBSTFA) in the presence of CsF and imidazole as catalysts enables a one-pot
peptide bond-forming reaction via activation and transient masking at C-termini
and N-termini, respectively. This versatile method tolerates various side chains,
while providing excellent yields without any racemization or polymerization.
W. Muramatsu, H. Yamamoto, J. Am. Chem. Soc.,
2021, 143, 6792-6797.
A mild, tantalum-catalyzed solvent-free approach for the construction of
amide bonds in the presence of 1-(trimethylsilyl)imidazole provides peptides in
high yields without any epimerization.
W. Muramatsu, H. Yamamoto, J. Am. Chem. Soc.,
2019, 141, 18926-18931.
In the presence of the Oxyma derivative 2,2-dimethyl-1,3-dioxolan-4-yl)methyl
2-cyano-2-(hydroxyimino)acetate, short peptides to oligopeptides could be
synthesized by using EDCI and NaHCO3 in water without measurable
racemization. Significantly, a simple basic and acidic aqueous workup procedure
can remove all reagents utilized in the reactions to afford only coupling
products in consistently excellent yields.
Q. Wang, Y. Wang, M. Kurosu, Org. Lett., 2012,
14, 3372-3375.
Mechanochemical coupling of peptide fragments containing highly
epimerization-prone and/or highly hindered amino acids at C-term provided
peptides in high yields and very low epimerization. Ball milling was clearly
identified as the key element to obtain such results.
Y. Yeboue, M. Jean, G. Subra, J. Martinez, F. Lamaty, T.-X. Métro, Org. Lett., 2021, 23,
631-635.
Borane-tetrahydrofuran complex or borane-methyl sulfide complex is used to
generate triacyloxyboranes, which can be effectively reacted with various
nucleophiles (alkylamines, arylamines, hydrazides, alcohols, phenols) at reflux
in toluene to provide the corresponding amides and esters in excellent yield.
Z. Huang, J. R. Reilly, R. N. Buckle, Synlett, 2007,
1026-1030.
The commercially available B(OCH2CF3)3 is as an
effective reagent for the direct amidation of a variety of carboxylic acids with
a broad range of amines. In most cases, products can be purified by a simple
filtration using commercially available resins, with no need for aqueous workup
or chromatography. The amidation of N-protected amino acids with both
primary and secondary amines proceeds effectively, with very low levels of
racemization.
R. M. Lanigan, P. Starkov, T. D. Sheppard, J. Org. Chem., 2013,
78, 4512-4523.
Carboxylic acids are converted into amides in moderate to high yields in
the presence of a stoichiometric amount of trimethylaluminium and amines in
toluene at 90˚C after 1 hour.
S. Chung, D. P. Uccello, H. Choi, J. I. Montgomery, J. Chen, Synlett, 2011,
2072-2074.
A method for the preparation of N-acylpyrroles involves condensation of
carboxylic acids with 2,4,4-trimethoxybutan-1-amine, followed by acid-mediated
cyclization to form the pyrrole ring. The preparative procedure is highly
tolerant of various functional groups.
T. Maehara, R. Kanno, S. Yokoshima, T. Fukuyama, Org. Lett., 2012,
14, 1946-1948.
The conversion of carboxylic acids to their corresponding acid chlorides occurs
rapidly in the presence of a tertiary amine base and 3,3-dichlorocyclopropenes via
aromatic cation-activated nucleophilic acyl substitution. The effect of
cyclopropene substituents on the rate of conversion is examined. Conditions were
developed for the preparation of acid sensitive acid chlorides.
D. J. Hardee, L. Kovalchuke, T. H. Lambert, J. Am. Chem. Soc., 2010,
132, 5002-5003.
A general, mild, and
highly chemoselective method for transamidation of unactivated tertiary amides
by a direct acyl N-C bond cleavage with non-nucleophilic amines is performed in the absence of transition metals and
operates under unusually mild reaction conditions. A direct amidation of abundant alkyl
esters affords amide bonds
with exquisite selectivity by acyl C-O bond cleavage.
G. Li, C.-L. Ji, X. Hong, M. Szostak, J. Am. Chem. Soc.,
2019,
141, 11161-11172.
Lanthanum trifluoromethanesulfonate is an effective catalyst for the coupling of
esters with amides to yield amides under mild conditions.
H. Morimoto, R. Fujiwara, Y. Shimizu, K. Morisaki, T. Ohshima, Org. Lett., 2014,
16, 2018-2021.
Aliphatic and/or aromatic esters were converted into the corresponding amides
under mild conditions in good to excellent yields in the presence of tert-butoxide,
water and air. The reaction is highly efficient, rapid, versatile, green and
economical, and could find great practical application in organic synthesis,
biochemistry, and industrial chemistry.
B. R. Kim, H.-G. Lee, S.-B. Kang, G. H. Sung, J.-J. Kim, J. K. Park, S.-G. Lee,
Y.-J. Yoon, Synthesis, 2012, 44,
42-50.
The use of magnesium nitride as a convenient source of ammonia allows a direct
transformation of esters to primary amides. Methyl, ethyl, isopropyl, and
tert-butyl esters are converted to the corresponding carboxamides in
good yields.
G. E. Veitch, K. L. Bridgwood, S. V. Ley, Org. Lett.,
2008,
10, 3623-3625.
Copper sulfate mediates a highly selective, mild, and rapid N-acylation of
various aliphatic and aromatic amines using thioacids in methanol at neutral
conditions. All N-acylated products of primary and secondary amines were
isolated in good yields. This method offers a simple workup, high yields, and is
is not sensitive to other functional groups such as phenols, alcohols, and
thiols.
S. M. Mali, R. D. Bhaisare, H. N. Gopi, J. Org. Chem., 2013,
78, 5550-5555.
A recently discovered precatalyst enables Pd-catalyzed Suzuki-Miyaura and
Buchwald-Hartwig reactions involving cleavage of a C(acyl)-O bond of aryl esters
as electrophiles under mild conditions. The Pd(II) precatalyst is highly active
due to its fast reduction to a Pd(0) active species.
A. H. Dardir, P. R. Melvin, R. M. Davis, N. Hazari, M. M. Beromi, J. Org. Chem.,
2018, 83, 469-477.
Formation of unstable but reactive acyl nitroso intermediates from Nα-protected
hydroxamic acids in the presence of iodine and DMSO enables an efficient and
straightforward coupling with an amino component to yield dipeptide esters.
M. Krishnamurthy, T. M. Vishwanatha, N. R. Panguluri, V. Panduranga, V. V.
Sureshbabu,
Synlett, 2015, 26, 2565-2569.
An iodine-NH3 • H2O system enables a direct transformation
of aryl, heteroaryl, vinyl, or ethynyl methyl ketones or carbinols to the
corresponding primary amides in good yields in aqueous media. A tandem
Lieben-Haller-Bauer reaction mechanism is proposed.
L. Cao, J. Ding, M. Gao, Z. Wang, J. Li, A. Wu, Org. Lett., 2009,
11, 3810-3813.
ZrOCl2 • 8 H2O is a highly effective, water-tolerant,
and reusable catalyst for the direct condensation of carboxylic acids and N,N′-dimethylurea
under microwave irradiation to give the corresponding N-methylamides in moderate
to excellent yields. ZrOCl2 • 8 H2O is a useful green catalyst
due to its low toxicity, easy availability, low cost, ease of handling, easy
recovery, good activity, and reusability.
D. Talukdar, L. Saikia, A. J. Thakur, Synlett, 2011,
1597-1601.
A general and efficient method enables the synthesis of tertiary amides from
readily available tertiary amines and anhydrides in the presence of FeCl2
as catalyst and tert-butyl hydroperoxide in water (T-Hydro) as oxidant.
Mechanistic studies indicated that the in situ-generated α-amino peroxide of
tertiary amine and iminium ion act as key intermediates.
Y. Li, L. Ma, F. Jia, Z. Li, J. Org. Chem., 2013,
78, 5638-5646.
A novel oxygen-centered radical addition between acyl peroxides and isocyanides
has been developed. A diverse collection of valuable arylcarboxyamides were
easily synthesized by this protocol. From the preliminary mechanistic study, the
elimination of carbon dioxide affords the product via an intramolecular
rearrangement.
M. Chen, Y. Li, H. Tang, H. Ding, K. Wang, L. Yang, C. Li, M. Gao, A. Lei, Org. Lett.,
2017, 19, 3147-3150.
The reaction of tert-butyl peroxybenzoate (TBPB) and ammonia/amines
provides the corresponding primary, secondary, and tertiary amides under
catalyst- and solvent-free conditions in excellent yields. TBPB is an efficient
and highly chemoselective benzoylating reagent for aliphatic amines in the
presence of aromatic amines and hydroxyl groups.
D. K. T. Yadav, B. M. Bhanage,
Synlett, 2015, 26, 1862-1866.
A Co-catalyzed oxidant-free reaction of carboxylic acids with organic azides
in the presence of tert-butyl isocyanide enables an effective synthesis
of N-sulfonylcarboxamides in very good yields. The protocol offers short
times, low temperatures, and broad substrate scope.
Y. Fang, Z.-Y. Gu, S.-Y. Wang, J.-M. Yang, S.-J. Ji, J. Org. Chem., 2018, 83,
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N-Cbz-protected amino acids reacted with various aryl amines in the
presence of methanesulfonyl chloride and N-methylimidazole in
dichloromethane to give the corresponding arylamides in high yields without
racemization under these mild conditions.
L. Mao, Z. Wang, Y. Li, X. Han, W. Zhou, Synlett, 2011,
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1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) catalyzes the amidation of acyl
imidazoles. The rate acceleration is especially evident with traditionally
unreactive, electron-deficient anilines. DBU offers safety and cost advantages
over more commonly employed catalysts such as 1-hydroxybenzotriazole (HOBt).
C. Larrive-Aboussafy, B. P. Jones, K. E. Price, M. A. Hardink, R. W. McLaughlin,
B. M. Lillie, J. M. Hawkins, R. Vaidyanathan, Org. Lett., 2010,
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Malonic acid derivatives undergo unusually mild decarboxylation in the
presence of N,N′-carbonyldiimidazole (CDI) at room temperature to
generate a carbonyl imidazole intermediate in high yield. Subsequent reactions with
various nucleophiles in an efficient one-pot process leads to amides, esters or carboxylic acids.
D. Lafrance, P. Bowles, K. Leeman, R. Rafka, Org. Lett., 2011,
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Deprotonated 1,2,4-triazole is an active acyl transfer catalyst suitable for
the aminolysis and transesterification of esters.
X. Yang, V. B. Birman, Org. Lett., 2009,
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Amines are efficiently acylated
by both cyclic and acyclic anhydrides in aqueous medium with sodium dodecyl
sulfate (SDS) - without use of acidic or basic reagents. Various amines and
anhydrides were reacted with equal ease. Chemoselective acylation in the
presence of phenols and thiols has been achieved. No chromatographic
separation is required for isolation of the acylated products.
S. Naik, G. Bhattacharjya, B. Talukdar, B. K. Patel,
Eur. J. Org. Chem., 2004, 1254-1260.
Various alcohols, thiols, phenols, and amines can be acetylated using acetic
anhydride in the presence of catalytic quantity of silver triflate. The method
proceeds under mild conditions, does not involve cumbersome workup, and the
resulting products are obtained in high yields within a reasonable time.
R. Das, D. Chakraborty, Synthesis, 2011,
1621-1625.
Phosphomolybdic acid (PMA) is a simple and efficient catalyst for the
acetylation of structurally diverse alcohols, phenols, and amines. Acetylation
reactions with acetic anhydride proceed in excellent yield in the presence of a
catalytic amount of PMA at ambient temperature within a relatively short
reaction time under solvent-free conditions.
S. T. Kadam, S. S. Kim, Synthesis, 2008,
267-268.
Copper(II) tetrafluoroborate efficiently catalyzes acetylation of
structurally diverse phenols, alcohols, thiols, and amines with
stoichiometric amounts of Ac2O under solvent-free conditions at
room temperature. Acid-sensitive alcohols are smoothly acetylated without
competitive side reactions.
A. K. Chakraborti, R. Gulhane, Shivani, Synthesis, 2004,
111-115.
Multivalent metal salts, such as ferric chloride and sulfate, are active and
versatile catalysts for the amidation of aliphatic fatty acids with long-chain
aliphatic amines.
Y. Terada, N. Ieda, K. Komura, Y. Sugi, Synthesis, 2008,
2318-2319.
Aliphatic, aromatic, and heteroaromatic carboxylic acids in the form of their
salts condense with aryl isocyanates at room temperature with loss of carbon
dioxide to give the corresponding amides in high yield. Application of the
reaction to acyl isocyanates gives unsymmetric imides. The reaction is
compatible with hydroxyl groups and both Fmoc and Boc protecting groups for
amines.
K. Sasaki, D. Crich, Org. Lett., 2011,
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2,2′-Dipyridyl diselenide catalyzes a direct reaction of carboxylic acids with
azides and trimethylphosphine at room temperature. The mechanism of the process,
which is not an aza-Wittig reaction, has been elucidated.
J. Burés, M. Martín, F. Urpí, J. Vilarrasa, J. Org. Chem., 2009,
74, 2203-2206.
The Staudinger ligation can be used to couple a peptide with a C-terminal
phosphinothioester to another with an N-terminal α-azido group to form a
single peptide that contains no residual atoms.
B. L. Nilsson, L. L. Kiessling, R. T. Raines,
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2-Acyl-4,5-dichloropyridazin-3-ones served as stable, convenient and
chemoselective N-acylating reagents for amines under neutral
conditions.
Y.-J. Kang, H.-A Chung, J.-J. Kim, Y.-J. Yoon, Synthesis,
2002, 733-738.
A straightforward trimethylsilylation protocol activates a thiol acid for
peptide bond formation at neutral pH using bistrimethylsilylacetamide (BSA). A
unique reactivity of the generated O-silylthionoesters toward amines
provides oxoamides.
W. Wu, Z. Zhang, L. S. Liebeskind, J. Am. Chem. Soc., 2011,
133, 14256-14259.
A novel amide bond formation strategy from simple thioacid and amine starting
materials is mediated by unstable but very reactive S-nitrosothioacid
intermediates. This fast reaction under mild conditions should be useful in
synthesis.
J. Pan, N. O. Devarie-Baez, M. Xian, Org. Lett., 2011,
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Thio FCMA intermediates, generated from the reactions of thioacids with
isonitriles, are active acyl donors, that form amide bonds under neutral
conditions.
Y. Rao, X. Li, S. J. Danishefsky, J. Am. Chem. Soc., 2009,
131, 12924-12926.
Thioacids derived from N-protected amino or polypeptide acids undergo facile
N-acylation with aromatic amines to afford aryl amides in good to excellent
yields and enantiopurities in the presence of iodine, 1-hydroxybenzotriazole and
N,N-diisopropylethylamine at room temperature. This oxidative Nα-acylation
also furnishes difficult-to-prepare N-Fmoc amino acid 4-nitroanilides in
good yields.
C. Madhu, T. M. Vishwanatha, V. V. Sureshbabu, Synthesis, 2013, 45,
2727-2736.
Microwave reactions of primary and secondary amines with
imidoylbenzotriazoles gave various polysubstituted amidines in good yields.
Convenient preparations of a variety of amides and imidoylbenzotriazoles
have also been developed using microwave irradiation under mild conditions
and short reaction times.
A. R. Katritzky, C. Cai, S. K. Singh, J. Org. Chem., 2006,
71, 3375-3380.
Various alcohols, phenols, amines and thiols
may easily be converted into acetate derivatives by treatment
with acetic anhydride in the presence of
acetonyltriphenylphosphonium bromide in good yields at room
temperature. With the same precatalyst, both aliphatic and aromatic aldehydes
can be transformed into the corresponding gem-diacetates under reflux
conditions.
A. T. Khan, L. H. Choudry, S. Ghosh, Eur. J. Org. Chem., 2005,
2782-2787.
Acyl halide-methanol mixtures are efficient reagents for the one-pot
transformation of t-butyl carbamates into amides. This transformation
can be carried out in the presence of a benzyloxycarbonyl group.
A. Nazih, D. Heissler, Synthesis,
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An efficient dynamic kinetic resolution of amines combines a ruthenium-catalyzed racemization with a lipase-catalyzed
resolution. A variety of primary amines were transformed into
one enantiomer of the amide in high yield and high enantioselectivity.
J. Paetzold, J. E. Bäckvall, J. Am. Chem. Soc.,
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127, 17620-17621.
A practical procedure for an efficient dynamic kinetic resolution of primary
amines employs a palladium nanocatalyst as racemization catalyst, a commercial
lipase as resolution catalyst, and ethyl acetate or ethyl methoxyacetate as acyl
donor. Various amines and one amino acid amide have been resolved with good
yields and high enantiomeric excesses.
M.-J. Kim, W.-H. Kim, K. Han, Y. K. Choi, J. Park, Org. Lett., 2007,
9, 1157-1159.
A practical procedure for an efficient dynamic kinetic resolution of primary
amines employs a palladium nanocatalyst as racemization catalyst, a commercial
lipase as resolution catalyst, and ethyl acetate or ethyl methoxyacetate as acyl
donor. Various amines and one amino acid amide have been resolved with good
yields and high enantiomeric excesses.
M.-J. Kim, W.-H. Kim, K. Han, Y. K. Choi, J. Park, Org. Lett., 2007,
9, 1157-1159.
A mild, versatile, copper-catalyzed three-component coupling of organoindium reagents
with imines and acid chlorides provides α-substituted amides or N-protected amines in a single step with the sole byproduct
being indium trichloride.
D. A. Black, B. A. Arndtsen, Org. Lett.,
2006,
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A simple, practical, and catalytic method for the N-formylation in the presence
of molecular iodine as a catalyst under solvent-free conditions is applicable to
a wide variety of amines. α-Amino acid esters can be converted without
epimerization.
J.-G. Kim, D. O. Jang, Synlett, 2010,
2093-2096.
A simple, mild method for N-formylation in the presence of indium metal
as a catalyst under solvent-free conditions is applicable to the chemoselective
reaction of amines and α-amino acid esters without epimerization.
J.-G. Kima, D. O. Jang, Synlett, 2010,
1231-1234.
Formyloxyacetoxyphenylmethane is a stable, water-tolerant, N-formylating
reagent that can be used under mild, solvent-free conditions for the preparation
of a range of N-formamides, N-formylanilines, N-formyl-α-amino
acids, N-formylpeptides, and isocyanides.
R. S. L. Chapman, R. Lawrence, J. M. J. Williams, S. D. Bull, Org. Lett.,
2017, 19, 4908-4911.
A mild, simple, and selective N-formylation of amines with formic
acid in the presence of ZnO under solvent-free conditions gives products in
excellent yields.
M. Hosseini-Sarvari, H. Sharghi, J. Org. Chem., 2006,
71, 6652-6654.
Various tertiary benzanilide derivatives were effectively synthesized in high
yields from a broad range substituted benzoic acid and N-monoalkylated
anilines using dichlorotriphenylphosphorane in chloroform. Allyl, Boc, MPM and
the Z group were unaffected under these conditions.
I. Azumaya, T. Okamoto, F. Imabeppu, H. Takayanagi,
Tetrahedron, 2003, 59, 2325-2331.
In the presence of sodium acetate, the reaction between 2,2,6-trimethyl-4H-1,3-dioxin-4-one
and secondary or tertiary alcohols or primary or secondary amines could be
carried out in refluxing tetrahydrofuran. Under these much milder conditions,
side products were avoided, and β-keto esters and β-ketoamides were normally
obtained in quantitative yields.
V. Sridharan, M. Ruiz, J. C. Menéndez, Synthesis, 2010,
1053-1057.
An amidation of unactivated esters with amino alcohols catalazyed by a
stable nitrogen-heterocyclic carbene is described. The mechanism is
discussed.
M. Movassaghi, M. A. Schmidt, Org. Lett., 2005,
7, 2373-2376.
A direct enantioselective copper hydride (CuH)-catalyzed synthesis of
β-chiral amides from α,β-unsaturated carboxylic acids and secondary amines under
mild reaction conditions tolerates a variety of functional groups in the β-position
including several heteroarenes. A subsequent iridium-catalyzed reduction to
γ-chiral amines can be performed in the same flask.
A. Link, Y. Zhou, S. L. Buchwald,
Org. Lett., 2020, 22, 5666-5670.
LiNTf2 is able to activate cyclic esters towards ring opening with a
stoichiometric amount of amines, thus leading to clean open-chain amides under
mild conditions. The generality of the method was demonstrated by a range of
selected lactones and amines.
C. Lalli, A. Trabocchi, G. Menchi, A. Guarna, Synlett, 2008,
189-192.
A small library of α,β-unsaturated oxindoles was
prepared by an efficient microwave-assisted one-pot sequence comprising an
aromatic substitution followed by an ionic Horner-Wadsworth-Emmons olefination.
A. Teichert, K. Jantos, K. Harms, A. Studer, Org. Lett., 2004,
6, 3477-3480.
Various alcohols, amines and N-hydroxylamines gave corresponding
formylated adducts in high yields by treatment with 2,2,2-trifluoroethyl
formate (TFEF). Chemoselective formylation of a primary amine could be readily
achieved in the presence of an unprotected primary alcohol.
D. R. Hill, C.-N. Hsiao, R. Kurukulasuriya, S.
Wittenberger, Org. Lett., 2002, 4, 111-113.
Deoxo-Fluor is a versatile and
mild reagent for acyl fluoride generation and subsequent one-flask amide
coupling. The conversion of acids to amides and Weinreb amides and the use
of Deoxo-Fluor as peptide-coupling reagent have been explored. Products were
isolated after facile purification in good yields.
J. M. White, A. R. Tunoori, B. J. Turunen, G. I.
Georg, J. Org. Chem., 2004, 69, 2573-2576.
A stereoconservative protection and deprotection method
of amino and carboxyl groups includes the generation of N-Phthaloyl N'-alkyl
secondary amides from N-phthaloyl amino acids by using a mixed anhydride method. These secondary
amides have been transformed by thermal rearrangement of the intermediate nitrosoamides
to esters with retention of configuration and excellent yields.
D. M. Shendage, R. Froehlich, G. Haufe, Org. Lett., 2004, 6,
3675-3678.
Preparation of One-Carbon Homologated Amides from Aldehydes or Primary
Alcohols
M. K. Gupta, Z. Li, T. S. Snowden, Org. Lett., 2014,
16, 1602-1605.
Formation of N-alkenyl alkynylamides by N-acylation of imines with
alkynoyl chlorides and the subsequent cationic Au(I)/PPh3-catalyzed
cycloisomerization allows a convergent and rapid assembly of substituted
2-pyridones.
H. Imase, K. Noguchi, M. Hirano, K. Tanaka, Org. Lett.,
2008,
10, 3563-3566.
In the presence of trichloroisocyanuric acid, triphenylphosphine, and sodium
cyanamide, readily available carboxylic acids were converted into N-acylcyanamides
in good to excellent yields within some minutes at room temperature under
ultrasound irradiation. In addition, N-acyl-substituted imidazolones were
readily accessible through guanylation-cyclization of in situ generated N-acylcyanamides.
W. Phakhodee, D. Yamano, M. Pattarawarapan, Synlett, 2020,
31,
703-707.
Ynamides as coupling reagents enable a practical one-pot strategy for α-keto
amide bond formation under extremely mild reaction conditions. Diversely
structural α-ketoamides were afforded in very good yields. This reaction offers
wide functional group tolerance and has potential applications in synthetic and
medicinal chemistry.
J. Ma, X. Cui, J. Xu, Y. Tan, Y. Wang, X. Wang, Y. Li, J. Org. Chem., 2022, 87,
3661-3667.
A metal- and photocatalyst-free room-temperature amidation of amines with
feedstock phenacyl bromides provides α-ketoamides using molecular oxygen as an
oxidant as well as a source of oxygen. This visible light mediated and
base-promoted reaction offers good functional group tolerance (benzylic alcohol,
keto, cyano, nitro, halo, etc.), a broad substrate scope, and gram-scale
synthesis.
S. Das, S. Mondal, S. P. Midya, S. Mondal, E. Ghosh, P. Ghosh, J. Org. Chem., 2023, 88,
14847-14859.
An amination reaction of in situ generated gem-difluoro-enolates with
nitrosoarenes furnished α-ketoamides in very high yields. This nitroso aldol
reaction is very fast (typically completed within 5 min) and scalable and
tolerates various sensitive functional groups. Amination with azodicarboxylates
smoothly produced fluorinated α-amino ketones.
M. K. Reddy, I. Ramakrishna, M. Baidya, Org. Lett.,
2018, 20, 4579-4583.
A simple and efficient oxidative coupling of diazoesters and α-diazoketones
with NH4I provides primary oxamates and α-ketoamides in good yields. This metal-free protocol is performed
under mild conditions and has a wide substrate scope.
H. Wang, Y. Zhao, Y. Zheng, S. Fang, J. Li, X. Wan, J. Org. Chem., 2020, 85,
3050-3058.
The reaction of sulfoxonium ylides with primary or secondary amines afforded
α-ketothioamides in the presence of elemental sulfur, whereas α-ketoamides were
produced when I2 and TBHP were present. This simple, scalable
reaction proceeded well at room temperature, tolerated a range of functional
group, and generated the corresponding products in very good yields.
T. N. Chaubey, P. J. Borpatra, A. Sharma, S. K. Pandey, Org. Lett., 2022, 24,
8062-8066.