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
Dibrominative Spirocyclization of 2-Butynolyl Anilides: Synthesis of <i>gem</i>-Dibromospirocyclic Benzo[<i>d</i>][1,3]oxazines and Their Application in the Synthesis of 4<i>H</i>-Furo[3,2-<i>b</i>]indoles
The combination of catalytic aqueous hydrochloricacid (HCl) and N-bromosuccinimide (NBS) generated electrophilic brominemonochloride (BrCl), which readily induced spiroannulation of 2-alkynolyl anilides (n = 1–3) to form gem-dibromospirocyclic benzo[d][1,3]oxazines in up to 92% yield. The reaction occurred under mild and metal-free conditions using EtOAc as a green solvent. The resulted spirocyclic
催化盐酸水溶液(HCl)和N-溴代琥珀酰亚胺(NBS)的结合产生亲电的一氯化溴(BrCl),该溶液很容易诱导2-炔基苯甲酰胺(n = 1-3)的螺环化反应,形成宝石-二溴螺环苯并[ d ] [1,3]恶嗪的产率高达92%。反应在温和且无金属的条件下进行,使用EtOAc作为绿色溶剂。所得的螺环产物包含苯并[ d ] [1,3]恶嗪,其既可以用作药效基团,也可以用作合成前体。此外,当前协议允许毫不费力地引入sp 3 - gem-二溴碳与空间要求很高的螺环中心相邻。这些螺旋杂环(n = 1)被证明具有通用性,并且操作方便。这些螺环的碱促进的脱溴化芳构化以极好的收率掩盖了稀有的和合成上有用的2-芳基-3-溴呋喃。这些3-溴呋喃是分子内Ullmann C–N键偶合以构建难以制备的4 H -furo [3,2- b ]吲哚的合适底物。另外,当前的方案是灵活的并且可适应于制备宝石-二氯化物变体。
Copper-catalysed intramolecular O-arylation: a simple and efficient method for benzoxazole synthesis
作者:Fengtian Wu、Jie Zhang、Qianbing Wei、Ping Liu、Jianwei Xie、Haojie Jiang、Bin Dai
DOI:10.1039/c4ob02068e
日期:——
An efficient protocol has been developed for the copper-catalysed intramolecular cyclization of N-(2-iodo-/bromo-/chloro-phenyl)benzamides for the synthesis of 2-substituted benzoxazoles.