.alpha.-Keto Amides and 1,2-Diketones from N,N'-Dimethoxy-N,N'-dimethylethanediamide. A Synthetic and Mechanistic Investigation
作者:Mukund P. Sibi、Mali Marvin、Rajiv Sharma
DOI:10.1021/jo00121a021
日期:1995.8
N,N'-Dimethoxy-N,N'-dimethylethanediamide (1), a 1,2-dicarbonyl synthon prepared from oxalyl chloride, undergoes nucleophilic displacements with Grignard reagents to provide alpha-keto amides 2-12 in 28-90% yields. The synthon also undergoes double nucleophilic displacements with organolithium reagents to furnish symmetrical 1,2-diketones 15-23 in 15-84% yields. A mechanism accounting for all the products from the reaction of 1 with nucleophiles has been proposed. Several control experiments were carried out to support the proposed mechanism.
N,N′-Dimethoxy-N,Nt́-Dimethylethanediamide: A Useful α-Oxo-N-Methoxy-N-Methylamide and 1,2-Diketone Synthon
作者:Mukund P. Sibi、Rajiv Sharma、Kevin L. Paulson
DOI:10.1016/0040-4039(92)88108-h
日期:1992.4
N,N'-Dimethoxy-N,N'-dimethylethanediamide on treatment with one to two equivalents of alkyl, aryl, and benzyl Grignard reagents provide alpha-oxo-N-methoxy-N-methylamides in good to excellent yields and on reaction with excess aryllithiums furnish moderate to good yields of symmetrical 1,2-diarylketones.
Novel Synthesis of 2-Oxo-4-phenyl-3-butynoic Acid, a New Inhibitor and Alternate Substrate of Pyruvate Decarboxylase
作者:Chingfan C. Chiu、Frank Jordan
DOI:10.1021/jo00098a041
日期:1994.9
An improved method is reported for the synthesis of 2-oxo acids and is applied to the synthesis of 2-oxo-4-phenyl-3-butynoic acid. The compound is synthesized by reacting the N-methoxy-N-methylamide of monoethyloxalic acid with lithium phenylacetylide yielding ethyl 2-oxo-4-phenyl-3-butynoate (78% yield), followed by strictly pH-controlled hydrolysis to the free acid in nearly quantitative yield. The compound is shown to be a potent irreversible inhibitor of brewers' yeast pyruvate decarboxylase, in addition to producing both cis- and trans-cinnamic acids as products of turnover. The formation of these isomeric cinnamic acids can be rationalized if the thiamin diphosphate-bound alpha-carbanion/enamine intermediate resulting from decarboxylation is protonated at the side chain gamma carbon to form two diastereomeric allenols, whose tautomerization and hydrolysis lead to the two products.
Chiu Chingfan C., Jordan Frank, J. Org. Chem, 59 (1994) N 19, S 5763-5766