Synthesis of substituted carboxylic acids, esters and amides
Indium(III) halide catalyzed the coupling of alkyl chlorides with silyl enolates derived from esters, ketones, and aldehydes to give various α-alkylated carbonyl compounds. A one-pot, three-component reactions of aldehyde enolates, alkyl chlorides, and allylsilanes or alkynylsilanes is described.
Y. Nishimoto, M. Yasuda, A. Baba, Org. Lett., 2007, 9, 4931-4934.
Carboindation of various alkenes such as ethylene, 1-alkenes, and cyclic alkenes with indium tribromide enables a regioselective reaction with ketene silyl acetals. The alkylindium product from the carboindation of cyclohexene revealed an anti addition mechanism.
Y. Nishimoto, H. Ueda, Y. Inamoto, M. Yasuda, A. Baba, Org. Lett., 2010, 12, 3390-3393.
In a borrowing hydrogen methodology, cobalt complexes stabilized with pincer ligands catalyze especially challenging alkylations of unactivated esters and amides with alcohols as alkylating reagents.
N. Deibl, R. Kempe, J. Am. Chem. Soc., 2016, 138, 10786-10789.
An effective and robust iridium pincer complex achieves a selective α-alkylation of tertiary and secondary acetamides involving a borrowing hydrogen methodology. The method tolerates alcohols bearing various functional groups. This presents a convenient and environmentally benign protocol for α-alkylation of amides.
L. Guo, Y. Liu, W. Yao, Y. Leng, Z. Huang, Org. Lett., 2013, 15, 1144-1147.
Atom-transfer radical (ATR) reaction of alkenes with alkyl bromides under irradiation using a low-pressure Hg lamp give addition/reduction products in good yield. Hydrogen bromide, formed by H-abstraction of a bromine radical from alkenes, is likely to play a key role in the reductive ATR reaction.
S. Sumino, A. Fusano, I. Ryu, Org. Lett., 2013, 15, 2826-2829.
A mild Suzuki-Miyaura cross-coupling reaction achieves the synthesis of a broad range of β,γ-alkynyl esters and amides using air-stable potassium alkynyltrifluoroborates as nucleophilic partners. Propargyl esters and amides were obtained in high yields using a low catalyst loading.
G. A. Molander, K. M. Traister, Org. Lett., 2013, 15, 5052-5055.
A general, inexpensive, copper-catalyzed coupling of terminal alkynes with diazo compounds provides ready access to 3-alkynoates. This reaction proceeds efficiently under nonbasic conditions at room temperature and tolerates various functional groups.
A. Suárez, G. C. Fu, Angew. Chem. Int. Ed., 2004, 43, 3580-3582.
The room-temperature nucleophilic addition of vinyl azides to propargylic alcohols in the presence of a catalytic amount of BF3·Et2O provides 4-ynamides. The procedure is operationally convenient, shows broad substrate scope, and tolerates many functional groups. Further, a Vilsmeier intramolecular cyclization of 4-ynamides gives dihydrofuran-2(3H)-ones with the alkyne group as the nucleophile.
J. Zheng, J.-H. Lin, L.-Y. Yu, Y. Wei, X. Zheng, J.-C. Xiao, Org. Lett., 2015, 17, 6126-6129.
Acrylamide and aromatic aldehydes were found to undergo the Baylis-Hillman reaction at ambient temperature and pressure in an aqueous medium in the presence of a stoichiometric amount of DABCO, to give the corresponding 3-hydroxy-2-methylenepropionamides in excellent yield. A faster, but reversible side reaction gave N-acylhemiaminals, which later disappeared, as the desired Baylis-Hillman adducts were formed as major products over an extended period of time.
C. Yu, L. Hu, J. Org. Chem., 2002, 67, 219-223.
A palladium-catalyzed coupling of aryl halides and ester enolates produced α-aryl esters in high yields at room temperature. The reaction was highly tolerant of functionalities and substitution patterns on the aryl halide. Improved protocols for the selective monoarylation of tert-butyl acetate and the efficient arylation of α,α-disubstituted esters were developed with LiNCy2 as base and P(t-Bu)3 as ligand.
M. Jřrgensen, S. Lee, X. Liu, J. P. Wolkowski, J. F. Hartwig, J. Am. Chem. Soc., 2002, 124, 12557-12565.