Palladium-catalyzed ortho-nitration of 2-arylbenzoxazoles
摘要:
An efficient and general protocol for palladium-catalyzed chelation-assisted ortho-nitration of 2-arylbenzoxazoles has been developed. This nitration exhibits high regioselectivity for the substrates, and the reaction could tolerate many functional groups such as F, Cl, Br, CH3, CH3O, affording ortho-nitration products in moderate to good yields. Moreover, some 2-arylbenzoxazole heterocyclic analogues proceed well under this catalytic system. Further studies have been performed to obtain insight into the mechanism. (C) 2015 Elsevier Ltd. All rights reserved.
We report herein a two‐step one‐pot strategy for the synthesis of benzoxazoles from amides by using cesium fluoride/copper as catalysts. This approach involves the in situ generation of acyl fluorides from the corresponding amides, and the acyl fluorides undergo transamidation and cyclization to give benzoxazoles in good yields. In this work, the amide C−N bonds are activated by CsF to form the acyl
Palladium catalyzed C<sub>sp2</sub>–H activation for direct aryl hydroxylation: the unprecedented role of 1,4-dioxane as a source of hydroxyl radicals
作者:Kapileswar Seth、Manesh Nautiyal、Priyank Purohit、Naisargee Parikh、Asit K. Chakraborti
DOI:10.1039/c4cc06864e
日期:——
Direct aryl hydroxylation has been achieved via palladium-catalysed Csp2–H activation using versatile directing groups through unprecedented hydroxyl transfer from 1,4-dioxane.
Parallel Synthesis of a Library of Benzoxazoles and Benzothiazoles Using Ligand-Accelerated Copper-Catalyzed Cyclizations of <i>ortho</i>-Halobenzanilides
作者:Ghotas Evindar、Robert A. Batey
DOI:10.1021/jo051927q
日期:2006.3.1
A general method for the formation of benzoxazoles via a copper-catalyzed cyclization of ortho-haloanilides is reported. This approach complements the more commonly used strategies for benzoxazole formation which require 2-aminophenols as substrates. The reaction involves an intramolecular C−O cross-coupling of the ortho-haloanilides and is believed to proceed via an oxidative insertion/reductive elimination
demonstrated broad substrate scope and good compatibility of functional groups. 2-Aryl benzothiazole and 2-aryl benzoimidazole could be smoothly assembled in the same manner. On the basis of preliminary mechanisticstudies, base initiated and aromatization driven β-carbon elimination was considered to be the key step for the formation of 2. This reaction offers an alternative, facile, and sustainable route to
Synthesis of benzoxazoles <i>via</i> the copper-catalyzed hydroamination of alkynones with 2-aminophenols
作者:Kohei Oshimoto、Hiroaki Tsuji、Motoi Kawatsura
DOI:10.1039/c9ob00572b
日期:——
describe herein the synthetic method to benzoxazole derivatives via the copper-catalyzed hydroamination of alkynones with 2-aminophenols. The method produced a wide variety of functionalized benzoxazole derivatives in good yields. Preliminary mechanistic experiments revealed that the reaction would proceed through the copper-catalyzed hydroamination of alkynones and the sequential intramolecular cyclization