Pd-catalyzed halocyclizations of unactivated 1,6-diynes through a formal anti-carbopalladation/bromide radical cascade  

作　　者：Zhihua Wang Li Wei Zhendong Cheng Jianhui Xia Zhiyuan Chen 

机构地区：[1]Key Laboratory of Functional Small Organic Molecules,Ministry of Education and Jiangxi Key Laboratory of Green Chemistry,College of Chemistry&Chemical Engineering,Jiangxi Normal University,Nanchang 330022,China

出　　处：《Chinese Chemical Letters》2021年第9期2756-2760,共5页中国化学快报（英文版）

基　　金：National Natural Science Foundation of China(No.21961015);the Natural Science Foundation of Jiangxi Province(No.20202ACBL203005)for financial support;the Open Project Program of Polymer Engineering Research Center,Jiangxi Science&Technology Normal University(No.KFGJ18014)。

摘　　要：We report a Pd-catalyzed halocyclization of unactivated 1,6-diynes with N-bromosuccinimide(NBS).This approach produces stereo-defined dibromo substituted dihydropyrans,tetrahydropyridines,and 3-methylene cyclohexenes with exocyclic double bond appendages in mostly good yields.Copper salt was found to be a useful Lewis acid in this reaction.Mechanistically,a formal anti-carbopalladation and a bromide radical promoted PdⅡ-PdⅢ-PdⅠ-PdⅡcatalytic cycles were proposed to be involved in the formation of the dibromo-substituted products.Further functionalization of the dihydropyran derivatives underwent B(C6F5)3-catalyzed ring opening,and reduction afforded dibrominated 1,3-dienes with excellent stereoselectivity.

关 键 词：Palladium catalysis HALOCYCLIZATION Unactivated diyne anti-Carbopalladation Bromide radical 1 3-Diene 

分 类 号：O621.251[理学—有机化学]