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

Abstract

A straightforward and efficient copper(I)/amino acid-catalyzed intramolecular Ullmann-type C-O coupling reaction has been developed. This protocol affords a facile methodology for the synthesis of a series of novel 2,4,5-substituted oxazoles from readily accessible N-acyl-2-bromo enamides under mild conditions.

Synthesis of 1,2,4‐Triazolo[4,3‐a]pyridines and Related Heterocycles by Sequential Condensation and Iodine‐Mediated Oxidative Cyclization

“…A plausible reaction mechanism for the formation of 1,2,4‐triazolo[4,3‐ a ]pyridine is proposed (Scheme ). Taking the formation of 1 a as an example, the base‐promoted oxidative iodination of hydrazone 4 a produces a plausible iodo species A . Then, the pyridine nitrogen attacks the iodo‐substituted carbon in A to generate intermediate B through a S N 2′‐type cyclization, which forms a new C−N bond.…”

“…Taking the formation of 1a as an example, the base-promoted oxidative iodination of hydrazone 4a produces ap lausible iodo species A. [25] Then, the pyridine nitrogen attacks the iodo-substituted…”

Crystal structure ofN-(tert-butoxycarbonyl)glycyl-(Z)-β-bromodehydroalanine methyl ester [Boc–Gly–(β-Br)(Z)ΔAla–OMe]

“…Further asymmetric hydrogenation of their double bound allows non-proteinogenic -amino acids and their derivatives to be obtained. Another important reaction of -bromo-,-dehydroamino acid derivatives in drug research is their coupling cyclization in which oxazole derivatives are produced (Liu et al, 2014).…”

A new synthesis of functionalized dialkyl maleate and fumarate derivatives by addition of amines to dialkyl acetylenedicarboxylates in the presence of NBS or NCS

“…The profound impact of enamine chemistry is well manifested by its widespread utility in transition metal catalysis and asymmetric transformations [7,8]. In this area, enaminoesters represent a broad class of key intermediates in organic synthesis, which has received considerable attention in recent years as starting materials for the synthesis of nitrogen-containing heterocycles [9][10][11] and wide variety of biologically active compounds [12][13][14]. Several methods have been reported previously for their preparation based upon direct condensation of b-ketoesters and amine in the presence of lewis acid catalysis [15], addition of ester enolates to nitriles and tosyl imines [16], addition of amine to alkynes [17], and reaction of dialkylformamides with zinc ester enolates [18].…”