α,β-Unsaturated Carboxylic Acid Derivatives. XII. A Convenient Synthesis of Oxazole-4-carboxylic and 3,3-Dibromo-2,2-diamino Acids

Abstract

Treatment of t-butyl 2-acetylamino-3-bromo-2-alkenoate with triethylamine gave t-butyl 5-alkyl-2-methyloxazole-4-carboxylate by dehydrobromination, but no reaction occurred with primary amines. While treatment of t-butyl 2-acetylimino-3,3-dibromoalkanoate with hydroxylamine or several aliphatic and aromatic primary amines gave addition products, t-butyl 2-acetylamino-3,3-dibromo-2-(hydroxyamino)- and 2-(substituted amino)alkanoate, respectively, in fairly good yields.

A concise approach to polysubstituted oxazoles from N-acyl-2-bromo enamides via a copper(i)/amino acid-catalyzed intramolecular C–O bond formation

“…However, despite the elegance of these oxidative strategies, the non-oxidative coupling strategy ( path b) remains an important alternative, particularly in the context of constructing oxazoles containing oxidant-sensitive substructures, which is still not sufficiently developed. Transformation of N-(2-halovinyl)amides (isolated or generated in situ) to oxazoles could be achieved by using organic or inorganic bases, [24][25][26][27] which, nevertheless, were limited by scope of the substrates and/or efficiency of the transformation. Recently, Ila et al developed the synthesis of 2,4,5substituted oxazoles from N-(2-methylthiovinyl)benzamides mediated by Ag 2 CO 3 28 or catalyzed by CuI.…”

4-Bis(methylthio)methylene-2-phenyloxazol-5-one: Versatile Template for Synthesis of 2-Phenyl-4,5-functionalized Oxazoles

“…Methods for direct construction of oxazole ring range over a variety of reactions and starting materials. Some of the oldest and most widely used methods for substituted oxazoles include cyclodehydration of α-acylaminocarbonyl compounds (Robinson−Gabriel synthesis), , the Cornforth and Cornforth method improved by Yokoyama, the biomimetic dehydrative cyclization of β-hydroxy amides to oxazolines and their oxidative dehydrogenation, − the Hantsch-type reaction of α-halo/acyloxy carbonyl compounds with amides, the rhodium-catalyzed decomposition of α-diazocarbonyl compounds in the presence of nitriles, and the photolysis/pyrolysis of α-acylisoxazolones . However, these methods genuinely lack universality and suffer from one or more drawbacks such as modest to poor yields, harsh reaction conditions, longer reaction time, and reactive starting materials with limited stability, which make them incompatible for the range of tolerated functional groups in the target oxazole.…”

Oxazole chemistry. A review of recent advances

“…Compounds of this type are claimed to lower the concentration of cholesterol, triglycerides and other lipids in blood serum. When tert-butyl 2-acetylamino-3-bromocrotonate 19 is treated with triethylamine, cyclization takes place to yield terf-butyl 2,5-dimethyloxazole-4-carboxylate 20 (19). carboxylation of 30, X = S, gives 2-(2-thienyl)oxazole (31).…”