Categories: C-C Bond Formation > Oxygen-containing molecules > Carboxyl derivatives >
Synthesis of β-hydroxy carboxylic acids, esters and amides
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Catalytic Bu4NOAc as silicon activator of ethyl
2-(trimethylsilyl)acetate enables the synthesis of β-hydroxy esters, whereas
catalytic Bu4NOTMS provides α,β-unsaturated esters. The established
reaction conditions were applicable to a diverse range of aromatic,
heteroaromatic, aliphatic aldehydes and ketones.
M. Das, A. Manvar, I. Fox, D. J. Roberts, D. F. O'Shea,
Synlett, 2017, 28, 2401-2406.
Activation of the silicon-carbon bond of α-trimethylsilylethylacetate in the
presence of P(i-PrNCH2CH2)3N as catalyst
allows an efficient synthesis of β-hydroxyesters and α,β-unsaturated esters.
Selectivity for either of these two products can be achieved simply by altering
the catalyst loading and reaction temperature.
K. Wadhwa, J. G. Verkade, J. Org. Chem., 2009,
74, 4368-4371.
An efficient and simple Cu-catalyzed Reformatsky reaction of carbonyl compounds
with ethyl iodoacetate provides excellent yields of β-hydroxyl esters using
inexpensive starting materials under mild reaction conditions.
L. Ouyang, J. H. Liao, Y. P. Xia, R. S. Luo, Synlett, 2020,
31,
1418-1422.
Boron compounds and a mild organic base (DBU) mediate a carboxylic acid
selective aldol reaction. Electron-withdrawing groups in amino acid derivative
ligands reacted with BH3·SMe2 forms a boron promoter with
increased Lewis acidity at the boron atom, which facilitated the carboxylic acid
selective enolate formation. The reaction tolerates other carbonyl groups such
as amides, esters, ketones, or aliphatic aldehydes.
H. Nagai, Y. Morita, Y. Shimizu, M. Kanai, Org. Lett.,
2016, 18, 2276-2279.
A proazaphosphatrane is a very efficient catalyst for Mukaiyama aldol reactions
of aldehydes with trimethylsilyl enolates in THF solvent. The reaction
conditions are mild and operationally simple, and a variety of aryl functional
groups, such as nitro, amino, ester, chloro, trifluorometh yl, bromo, iodo,
cyano, and fluoro groups, are tolerated.
V. R. Chintareddy, K. Wadhwa, J. G. Verkade, J. Org. Chem., 2009,
74, 8118-8132.
Rh-DuPhos catalyzes an in situ conjugate reduction of an unsaturated carbonyl
compound with Cl2MeSiH to provide an (E)-silylketene acetal.
This enolate undergoes a noncatalyzed reaction with a variety of aldehydes to
give the derived syn-aldol adducts in high yields and diastereoselection.
C.-X. Zhao, J. Bass, J. P. Morken,
Org. Lett., 2001, 3, 2839-2842.
A direct enantioselective α-hydroxymethylation of aldehydes employing an
α,α-diarylprolinol trimethylsilyl ether organocatalyst enables efficient access
to β-hydroxycarboxylic acids and δ-hydroxy-α,β-unsaturated esters via an
intermediate lactol in good yields, excellent enantioselectivity, and
compatibility with a broad range of functional groups in the aldehyde.
R. K. Boeckman, K. F. Biegasiewicz, D. J. Tusch, J. R. Miller, J. Org. Chem.,
2015,
80, 4030-4045.
Acetic Acid Aldol Reactions in the Presence of Trimethylsilyl
Trifluoromethanesulfonate
C. W. Downey, M. W. Johnson, D. H. Lawrence, A. S. Fleisher, K. J. Tracy, J. Org. Chem., 2010,
75, 5351-5354.
The choice of either the solvent or temperature determines the
diastereoselectivity during the enolboration-aldolization of methyl
phenylacetate. In CH2Cl2, the reaction favors the anti-pathway
at -78 °C and the syn-pathway at rt. Conversely, the reaction produces
the anti-isomer up to rt and the syn-isomer at refluxing
temperatures in nonpolar solvents.
P. V. Ramachandran, P. B. Chanda, Org. Lett., 2012,
14, 4346-4349.
The choice of either the solvent or temperature determines the
diastereoselectivity during the enolboration-aldolization of methyl
phenylacetate. In CH2Cl2, the reaction favors the anti-pathway
at -78 °C and the syn-pathway at rt. Conversely, the reaction produces
the anti-isomer up to rt and the syn-isomer at refluxing
temperatures in nonpolar solvents.
P. V. Ramachandran, P. B. Chanda, Org. Lett., 2012,
14, 4346-4349.
Whereas a dicyclohexylboron triflate/triethylamine (Cy2BOTf/Et3N)-mediated
enolboration-aldolization reaction of methyl arylacetates provides anti-aldols
at low temperatures, a combination of a less bulky boron reagent (dibutylboron
triflate, Bu2BOTf), a bulky amine (iPr2NEt), and
ambient temperature is required to obtain syn-aldols.
A. Y. Thomas, T. L. Walls III, B. N. Nelson, S. W. Primeaux, P. B. Chanda, J. Org. Chem., 2021, 86,
6184-6194.
Whereas a dicyclohexylboron triflate/triethylamine (Cy2BOTf/Et3N)-mediated
enolboration-aldolization reaction of methyl arylacetates provides anti-aldols
at low temperatures, a combination of a less bulky boron reagent (dibutylboron
triflate, Bu2BOTf), a bulky amine (iPr2NEt), and
ambient temperature is required to obtain syn-aldols.
A. Y. Thomas, T. L. Walls III, B. N. Nelson, S. W. Primeaux, P. B. Chanda, J. Org. Chem., 2021, 86,
6184-6194.
The Mukayiama aldol reaction of aldehydes is efficiently catalyzed by a dimeric
alumatrane complex at mild or subambient temperatures. The protocol tolerates a
wide variety of electron-rich, neutral, and deficient aryl, alkyl, and
heterocyclic aldehydes. A wide variety of enol silyl ethers are also tolerated.
S. M. Raders, J. G. Verkade, J. Org. Chem., 2009,
74, 5417-5428.
N-Heterocyclic Carbene-Catalyzed Mukaiyama Aldol Reactions
J. J. Song, Z. Tan, J. T. Reeves, N. K. Yee, C. H. Senanayake, Org. Lett., 2007,
9, 1013-1016.
Reusable polymer-bound lithium dialkylamides were employed in crossed aldol reaction
of various carbonyl compounds with aldehydes to afford the corresponding
β-hydroxycarbonyl compounds. The introduction of spacer chains between the
base moiety and the polystyrene backbone increased the yields of the desired
aldol adducts.
A. Seki, F. Ishiwata, Y. Takizawa, M. Asami, Tetrahedron, 2004,
60, 5001-5011.
One-Pot Enol Silane Formation-Mukaiyama Aldol-Type Addition to Dimethyl
Acetals Mediated by TMSOTf
C. W. Downey, M. W. Johnson, K. J. Tracy, J. Org. Chem., 2008,
73, 3299-3302.
Simple thioesters undergo direct aldol addition to aldehydes in the presence
of a Lewis acid and i-Pr2NEt. The reactions proceed
extremely rapidly and in excellent yield.
J. M. Yost, G. Zhou, D. M. Coltart, Org. Lett.,
2006,
8, 1503-1506.
A novel method for Reformatsky-like reactions employs titanocene(III)
chloride as a mild and homogeneous single-electron reductant. The reactions
are simple, rapid and tolerate a wide range of functionalities. The addition
is anti selective.
J. D. Parrish, D. R. Shelton, R. D. Little, Org. Lett., 2003,
5, 3615-3617.
An easy, direct, general, and efficient samarium diiodide-mediated
preparation of 3-hydroxyacids in high yield by reaction of different
aldehydes or ketones with commercially available iodoacetic acid is
described.
J. M. Concellón, C. Concellón, J. Org. Chem., 2006,
71, 4428-4432.
A readily available chiral bisoxazolidine catalyzes the asymmetric Reformatsky
reaction between ethyl iodoacetate and aromatic aldehydes to yield
3-hydroxy-3-(4-aryl)propanoates in high yields and good enantioselectivities in
the presence of dimethylzinc and air at room temperature within 1 h. In contrast
to aromatic substrates, relatively low ee’s are obtained with aliphatic
aldehydes.
C. Wolf, M. Moskowitz, J. Org. Chem., 2011,
76, 6372-6376.
Efficient In- or In(I)-based diastereoselective Reformatsky-type reactions
of simple ketones, α-alkoxy ketones, and β-keto esters were developed. High
anti selectivity was established in the addition of the branched
α-halo ester derivatives to simple ketones using indium metal under
THF-refluxing conditions. Syn selective additions to α-alkoxy ketones
and β-keto esters required either In(I)X or In-InCl3 systems in
toluene under ultrasonication.
S. A. Babu, M. Yasusa, I. Shibata, A. Baba, J. Org. Chem.,
2005, 70, 10408-10419.
S. A. Babu, M. Yasusa, I. Shibata, A. Baba, J. Org. Chem.,
2005, 70, 10408-10419.
The addition of amide enolates to acylsilanes and a subsequent 1,2-Brook
rearrangement generate β-silyloxy homoenolates nucleophiles that undergo
smooth addition to alkyl halides, aldehydes, and ketones.
R. B. Lettan II, T. E. Reynolds, C. V. Galliford, K. A. Scheidt, J. Am. Chem. Soc., 2006,
128, 15566-15567.
A tandem Wittig Rearrangement/aldol reaction of O-benzyl or O-allyl
glycolate esters generates two carbon-carbon bonds and two contiguous
stereocenters with excellent diastereoselectivity in a single step from
simple starting materials. The [1,2]-Wittig rearrangement proceeds under
very mild reaction conditions.
M. B. Betrand, J. P. Wolfe, Org. Lett.,
2006,
8, 4661-4663.
Chiral rhodium(bisoxazolinylphenyl) complexes efficiently catalyze the
asymmetric reductive aldol reaction of aldehydes and α,β-unsaturated esters
with hydrosilanes to give the corresponding β-hydroxypropionates with high
anti-selectivity and enantioselectivity. The selectivity is discussed.
H. Nishiyama, T. Shiomi, Y. Tsuchiya, I. Matsuda, J. Am. Chem. Soc.,
2005,
127, 6972-6973.
A new strategy for the catalytic asymmetric aldol reaction of ketones was
developed that relies on a chiral copper(I) complex-catalyzed domino
reduction/aldol reaction sequence in the presence of phenylsilane.
J. Deschamp, O. Chuzel, J. Hannedouche, O. Riant, Angew. Chem. Int. Ed.,
2006,
45, 1292-1297.
The weakly acidic species, silicon tetrachloride (SiCl4), can be
activated by binding of a strongly Lewis basic chiral phosphoramide, leading
to in situ formation of a chiral Lewis acid for catalysis of the aldol
reaction of conjugated and nonconjugated aldehydes with silyl ketene acetals
and silyl dienol ethers (vinylogous aldol reactions). The high levels of
regio-, anti diastereo-, and enantioselectivity observed are
discussed.
S. E. Denmark, G. L. Beutner, T. Wynn, M. D. Eastgate, J. Am. Chem. Soc.,
2005,
127, 3774-3789..
C-H functionalization of benzyl silyl ethers by means of rhodium-catalyzed
insertions of aryldiazoacetates can be achieved in a highly
diastereoselective and enantioselective manner by judicious choice of chiral
catalyst or auxiliary. The use of (S)-lactate as a chiral auxiliary
resulted in C-H functionalization with moderate diastereoselectivity and
enantioselectivity. The best results were achieved using Hashimoto's Rh2((S)-PTTL)4
catalyst.
H. M. L. Davies, S. J. Hedley, B. R. Bohall, J. Org. Chem.,
2005,70, 10737-10742.
Related
An efficient carbene-catalyzed formal
[4 + 2] annulation of β-silyl enones with a HOBT ester followed by ring opening with nucleophiles
provides γ-keto-β-silyl esters and amides, most with extremely high
enantioselectivities. γ-Keto-β-silyl esters can be easily converted into
enantioenriched β,σ-dihydroxyl esters.
Y. Zhang, X. Huang, J. Guo, C. Wei, M. Gong, Z. Fu, Org. Lett., 2020, 22, 9545-9550.
The catalytic generation of activated carboxylates from epoxyaldehydes enables a direct, anti-selective, convenient and mild synthesis of β-hydroxyesters.
K. Y.-K. Chow, J. W. Bode, J. Am. Chem. Soc.,
2004,
126, 8126-8127.
A mild, Co2(CO)8-catalyzed carbonylative opening of
terminal epoxides under 1 atm of carbon monoxide at room temperature in methanol
provides β-hydroxy esters in good yields. This transformation tolerates
various functional groups.
S. E. Denmark, M. Ahmad, J. Org. Chem., 2007,
72, 9630-9634.
A pH-independent asymmetric transfer hydrogenation of β-keto esters in water
with formic acid/sodium formate can be conducted open to air and gives access to
β-hydroxy esters in excellent yields and selectivities.
M. A. Ariger, E. M. Carreira, Org. Lett., 2012,
14, 4522-4524.
A mild, enantioselective hydrosilylation of 3-oxo-3-arylpropionic acid
methyl or ethyl esters using axially chiral BINAM N-heterocyclic carbene (NHC)-Rh(III) complexes
as catalysts gave 3-hydroxy-3-arylpropionic acid
methyl or ethyl esters in good yields with good to excellent
enantioselectivities under mild conditions.
Q. Xu, X. Gu, S. Liu, Q. Duo, M. Shi, J. Org. Chem., 2007,
72, 2240-2242.