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
我们报告了未活化的1,6-二炔与N-溴代琥珀酰亚胺(NBS)的Pd催化卤代环化反应。这种方法可生产立体定义明确的二溴取代的二氢吡喃,四氢吡啶和3-亚甲基环己烯,并带有环外双键附件,且收率很高。发现铜盐是该反应中有用的路易斯酸。从机理上讲,提出了一种形式上的抗碳氢键合和溴化物自由基促进的Pd II -Pd III -Pd I -Pd II催化循环,参与了二溴取代产物的形成。将二氢吡喃衍生物进一步官能化后进行B(C 6 F 5)3-催化的开环并还原得到具有优异立体选择性的二溴代1,3-二烯。
Sonogashira coupling and Garratt–Braverman cyclization in tandem: formation of four C–C bonds leading to the synthesis of aryl dihydro isofurans and isoindoles
作者:Debaki Ghosh、Paramita Pal、Amit Basak
DOI:10.1016/j.tetlet.2015.02.093
日期:2015.4
In this Letter we report an interesting one pot synthesis of aryl dihydro isofurans and isoindoles, naturally occurring privileged skeletons, in excellent yields from easily accessible starting materials. The process involved carrying out three reactions in a tandem manner leading to 4 C-C bond formations, namely two Sonogashira couplings (2 x 1 C-C bond) followed by Garratt-Braverman Cyclization (2 C-C bond). (C) 2015 Elsevier Ltd. All rights reserved.