An operationally straightforward method for the amidation of aldehydes with economic ammonium chloride or amine hydrochloride salts enables the synthesis of various amides in good yield by using inexpensive copper sulfate or copper(I) oxide as a catalyst and aqueous tert-butyl hydroperoxide as an oxidant. Chiral amines can be used without detectable racemization.
S. C. Ghosh, J. S. Y. Ngiam, A. M. Seayad, D. T. Tuan, C. L. L. Chai, A. Chen, J. Org. Chem., 2012, 77, 8007-8015.
The use of diacetoxyiodobenzene in the presence of an ionic liquid enables a facile one-pot synthesis of a series of amides from aldehydes and amines at ambient temperature.
V. Prasad, R. R. Kale, B. B. Mishra, D. Kumar, V. K. Tiwari, Org. Lett., 2012, 14, 2936-2939.
A photoorganocatalytic reaction of aldehydes with diisopropyl azodicarboxylate leads to an intermediate carbonyl imide, which can react with a variety of amines to afford amides. This method enables a mild, one-pot, and environmentally friendly synthesis of amides from aldehydes and amines.
G. N. Papadopoulos, C. G. Kokotos, J. Org. Chem., 2016, 81, 7023-7028.
An oxidative amidation of aromatic aldehydes in the presence of low loadings of phenazine ethosulfate as an inexpensive metal-free visible light photocatalyst proceeds at ambient temperature and uses air as the sole oxidant. The operationally easy procedure provides an economical, green, and mild alternative for the formation of amide bonds.
D. Leow, Org. Lett., 2014, 16, 5812-5815.
Using an efficient visible-light photocatalysis-based method, a mixture of an aldehyde, tert-butyl hydrogen peroxide, and N-chlorosuccinimide afforded an acid chloride in the presence of Ru(bpy)3Cl2 as photocatalyst. A subsequent reaction with an amine provided the corresponding amide.
N. Iqbal, E. J. Cho, J. Org. Chem., 2016, 81, 1905-1911.
A copper-catalyzed aerobic oxidative cross-dehydrogenative coupling (CDC) of amines with α-carbonyl aldehydes leads to various α-ketoamides compounds. Many types of amines are tolerant in this transformation. Wide substrate scope, and the use of air as oxidant and initiator make this transformation highly efficient and practical.
C. Zhang, X. Zong, L. Zhang, N. Jiao, Org. Lett., 2012, 14, 3280-3283.
The use of PhI=NTs/PhI=NNs as the nitrogen source in the presence of inexpensive iron(II) chloride + pyridine as the in situ formed precatalyst enables amidation of aldehydes under mild conditions at room temperature or microwave assisted conditions. The protocol is operationally straightforward and accomplished in good product yields and with complete chemoselectivity.
T. M. U. Ton, C. Tejo, S. Tania, J. W. W. Chang, P. W. H. Chan, J. Org. Chem., 2011, 76, 4894-4904.
A N-heterocyclic carbene catalyzes the oxidative esterification of various aldehydes in the presence of 3,3',5'5-tetra-tert-butyldiphenoquinone to yield hexafluoroisopropylesters, which are useful active esters for in situ amide bond formation. This transition metal-free organocatalytic system also enabled a mild oxidative azidation of aldehydes.
S. De Sarkar, A. Studer, Org. Lett., 2010, 12, 1992-1995.
A mild and efficient oxidative amidation of aldehydes uses amine HCl salts and tert-butyl hydroperoxide as an oxidant in the presence of a copper catalyst.
W.-J. Yoo, C.-J. Li, J. Am. Chem. Soc., 2006, 128, 13064-13065.
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.
A metal-free oxidative-amidation strategy enables the synthesis of α-ketothioamides and amides from α-azido ketones. The C-H bond thionation of α-azido ketones with elemental sulfur could form α-ketothioacyl azide, which was then nucleophilically attacked by amines, while amides could be formed with the release of nitrogen gas and cyano anion in the presence of PhI(OAc)2.
P. Yu, Y. Wang, Z. Zeng, Y. Chen, J. Org. Chem., 2019, 84, 14883-14891.
A direct electrochemical amidation of α-ketoaldehydes and amines without electrolytes at ambient temperature enables a catalyst- and oxidant-free preparation of α-ketoamides with hydrogen as the sole byproduct. The reaction offers clean and mild conditions, excellent functional-group tolerance, and high atom economy and scalability.
J.-Y. Chen, H.-Y. Wu, Q.-W. Gui, X.-R. Han, Y. Wu, K. Du, Z. Cao, Y.-W. Lin, W.-M. He, Org. Lett., 2020, 22, 2206-2209.