Categories: C-N Bond Formation >
Synthesis of amides
The key to the success of a general catalytic procedure for the cross-coupling of primary amides and alkylboronic acids was the identification of a mild base (NaOSiMe3) and oxidant (di-tert-butyl peroxide) to promote the copper-catalyzed reaction in high yield. This transformation provides a facile, high-yielding method for the monoalkylation of amides.
S. A. Rossi, K. W. Shimkin, Q. Xu, L. M. Mori-Quiroz, D. A. Watson, Org. Lett., 2013, 15, 2314-2317.
The use of monodentate ligands that possess a methyl group ortho to the phosphorus center allows the coupling of various aryl and heteroaryl chlorides with various amides in high yield. These ligands can prevent the formation of the κ2-amidate complexes and thereby generate more stable catalysts for the amination of aryl chlorides.
T. Ikawa, T. E. Barder, M. R. Biscoe, S. L. Buchwald, J. Am. Chem. Soc., 2007, 129, 13001-13007.
A catalyst, based on a biarylphosphine ligand, for the Pd-catalyzed cross-coupling reactions of amides and aryl mesylates allows the transformation of an array of aryl and heteroaryl mesylates into the corresponding N-aryl amides in good yields.
K. Dooleweerdt, B. P. Fors, S. L. Buchwald, Org. Lett., 2010, 12, 2350-2353.
The Xantphos/Pd-catalyzed intermolecular coupling of aryl halides and amides displays good functional group compatibility, and the desired C-N bond forming process proceeds in good to excellent yields. The arylation of sulfonamides, oxazolidinones, and ureas was found to be highly dependent on reaction concentrations and catalyst loadings.
J. Yin, S. L. Buchwald, J. Am. Chem. Soc., 2002, 124, 6043-6048.
A mild and highly efficient direct synthesis of formanilides from structurally varied arylboronic acids involves a copper-catalyzed Chan-Lam coupling reaction between arylboronic acids and formamide in the presence of a base at room temperature. The strategy offers a valid and practical alternative to existing transformations especially as arylboronic acids are easily accessible, stable, and diversified substrates.
V. P. Srivastava, D. K. Yadav, A. K. Yadav, G. Watal, L. D. S. Yadav, Synlett, 2013, 24, 1423-1427.
The N-arylation of aromatic and aliphatic secondary acyclic amides as poor nucleophiles has been accomplished using a simple and cheap copper catalytic system. The corresponding tertiary acyclic amides have been obtained in good to excellent yields.
E. Racine, F. Monnier, J.-P. Vors, M. Taillefer, Org. Lett., 2011, 13, 2818-2821.
Microwave-assisted, palladium-catalyzed C-N bond-forming reactions with aryl/heteroaryl nonaflates and amines using soluble amine bases resulted in good to excellent yields of arylamines in short reaction times.
R. E Tundel, K. W. Anderson, S. L. Buchwald, J. Org. Chem., 2006, 71, 430-433.
The arylation of N-H and O-H containing compounds at room temperature with phenylboronic acids is promoted in the presence of cupric acetate and a tertiary amine. Substrates include phenols, amines, anilines, amides, imides, ureas, carbamates, and sulfonamides.
D. M. T. Chan, K. L. Monaco, R.-P. Wang, M. P. Winteres, Tetrahedron Lett., 1998, 39, 2933-2936.
A highly efficient Bi(OTf)3-catalyzed multicomponent synthesis of amidomethylated arenes and heteroarenes from readily available starting materials proceeds under mild conditions and has a broad substrate scope with water as the only side product.
A. E. Schneider, G. Manolikakes, Synlett, 2013, 24, 2057-2060.
The reaction of aromatic compounds with nitroethane in polyphosphoric acid allows the synthesis of acetamides in good yields. The corresponding amines can be obtained in situ upon hydrolysis of the acetamides.
A. V. Aksenov, N. A. Aksenov, O. N. Nadein, I. V. Aksenova, Synlett, 2010, 2628-2630.
Iridium-catalyzed allylation of potassium trifluoroacetamide or the highly reactive ammonia equivalent lithium di-tert-butyliminodicarboxylate forms a range of conveniently protected, primary, α-branched allylic amines in high yields, high branched-to-linear regioselectivities, and high enantiomeric excess.
M. J. Pouy, A. Leitner, D. J. Weix, S. Ueno, J. F. Hartwig, Org. Lett., 2007, 9, 3949-3952.
A mild and operationally simple hydroamidation of electron-deficient terminal alkynes by amides in the presence of a Pd-catalyst enables a stereoselective synthesis of Z-enamides. Hydrogen bonding between the amido proton and carbonyl oxygen of ester group maybe provides the extra stability to the Z-isomer of an intermediate vinyl-palladium complex, which subsequently undergoes protodepalladation and leads to the Z-enamide selectively.
N. Panda, A. K. Jena, J. Org. Chem., 2012, 77, 9407-9412.
Catalysts generated from Pd2(dba)3 and biphenyl ligands efficiently promote the coupling of amides and carbamates with unactivated vinyl triflates and tosylates, to provide enamides in good to excellent yields.
M. C. Willis, G. N. Brace, I. P. Holmes, Synthesis, 2005, 3229-3234.
1,1,1-Tris(hydroxymethyl)ethane as a New, Efficient, and Versatile Tripod Ligand for Copper-Catalyzed Cross-Coupling Reactions of Aryl Iodides with Amides, Thiols, and Phenols
Y.-J. Chen, H.-H. Chen, Org. Lett., 2006, 8, 5609-5612.
A versatile and efficient copper-catalyzed amidation of vinyl bromides and iodides has been developed. The protocol, which uses a combination of copper iodide and N,N'-dimethyl ethylenediamine, tolerates substrates bearing ester, silyl ether, and amino groups.
L. Jiang, G. E. Job, A. Klapars, S. L. Buchwald, Org. Lett., 2003, 5, 3667-3669.
A mild, ruthenium-catalyzed anti-Markovnikov addition of secondary amides, anilides, lactames, ureas, bislactames, and carbamates to terminal alkynes has been developped. Two complementary protocols provide either the E or the Z isomers.
L. J. Goossen, J. E. Rauhaus, G. Deng, Angew. Chem. Int. Ed., 2005, 44, 4042-4045.
A catalyst system generated in situ from bis(2-methallyl)(cycloocta-1,5-diene)ruthenium(II), 1,4-bis(dicyclohexylphosphino)butane, and ytterbium triflate promotes an anti-Markovnikov addition of primary amides to terminal alkynes under the formation of Z-configured secondary enamides. An in situ double-bond isomerization reaction using triethylamine and molecular sieves provides E-isomers.
L. J. Gooßen, M. Blanchot, F. S. M. Salih, K. Gooßen, Synthesis, 2009, 2283-288.
A general and efficient method for the coupling of a wide range of amides with alkynyl bromides using copper(II) sulfate-pentahydrate and 1,10-phenanthroline as catalyst leads to a structurally diverse array of ynamides including macrocyclic ynamides via an intramolecular amidation.
X. Zhang, Y. Zhang, J. Huang, R. P. Hsung, K. C. M. Kurtz, J. Oppenheimer, M. E. Petersen, I. K. Sagamanova, L. Shen, M. R. Tracey, J. Org. Chem., 2006, 71, 4170-4177.
In copper-catalyzed direct N-alkynylation, the use of pure and anhydrous K3PO4 provides higher ynamide yields in comparison to samples contaminated with hydrates (K3PO4 · 1.5 H2O and K3PO4 · 7 H2O). With high quality K3PO4, a number of ynamides were synthesized in good yields. In addition, ynamides can undergo regioselective hydroamination with carbamates.
K. Dooleweerd, H. Birkedal, T. Ruhland, T. Skrydstrup, J. Org. Chem., 2008, 73, 9447-9450.
A copper-catalyzed direct N-alkynylation of amides has been developed leading to a facile entry for syntheses of chiral ynamides.
M. O. Frederick, J. A. Mulder, M. R. Tracey, R. P. Hsung, J. Huang, K. C. M. Kurtz, L. Shen, C. J. Douglas, J. Am. Chem. Soc., 2003, 125, 2368-2369.
A facile route to ynamides in high yields was achieved through an iron-catalyzed C-N coupling reaction of amides with alkynyl bromides in the presence of 20 mol % of N,N′-dimethylethane-1,2-diamine (DMEDA).
B. Yao, Z. Liang, T. Niu, Y. Zhang, J. Org. Chem., 2009, 74, 4630-4633.
A rhodium-catalyzed N-H and O-H insertion of amides and carboxylic acids with α-diazo-β-ketoesters gives different α-amido- and α-carboxylic-β-ketoesters in good yields. The reactions were performed under mild conditions with 1 mol% of catalyst.
S. Bertelsen, M. Nielsen, S. Bachmann, K. A. Jorgensen, Synthesis, 2005, 2234-2238.
A range of enol triflates can be coupled with amides, carbamates, and sulfonamides using palladium catalysis. This method allows the synthesis of enamides, which may not be readily available by other means.
D. J. Wallace, D. J. Klauber, C.-Y. Chen, R. P. Volante, Org. Lett., 2003, 5, 4749-4752.
Several amides were obtained in high yields by an efficient method from the corresponding imines which are readily prepared from aldehydes. This procedure involves the oxidation of aldimines with m-CPBA and BF3·OEt2. In this reaction, the product is strongly influenced by the electron releasing capacity of the aromatic substituent (Ar).
G. An, M. Kim, J. Y. Kim, H. Rhee, Tetrahedron Lett., 2003, 44, 2183-2186.
An intramolecular vinylation of various iodoenamides using CuI as the catalyst and N,N'-dimethylethylenediamine as the ligand led to five- to seven-membered lactams in moderate to excellent yields.
T. Hu, C. Li, Org. Lett., 2005, 7, 2035-2038.
A convenient and efficient iron-catalyzed aminobromination of alkenes has been developed using inexpensive FeCl2 as the catalyst, amides/sulfonamides and NBS as the nitrogen and bromine sources, respectively, under mild conditions.
Z. Wang, Y. Zhang, H. Fu, Y. Jiang, Y. Zhao, Synlett, 2008, 2667-2668.