One Pot Access to 2′‐Aryl‐2,3′‐Bithiophenes via Twofold Palladium‐Catalyzed C−X/C−H Coupling Associated to a Pd‐1,4‐Migration

Abstract

AbstractThe reactivity of 1,2‐dihalobenzenes in palladium catalyzed polyheteroarylation via C−H bond functionalization was investigated. The first catalytic cycle using thiophene as the heteroarene gives the expected 2‐(2‐bromophenyl)thiophenes. In the course of the second catalytic cycle, in the presence of heteroarenes having a free C3‐position, a partial Pd‐1,4‐migration occurred giving rise to aryl‐substituted biheteroarenes such as 2′‐aryl‐2,3′‐bithiophenes as well as the expected 1,2‐di(thiophen‐2‐yl)benzenes. The best selectivities in favor of the formation of 2′‐aryl‐2,3′‐bithiophenes were obtained with electron‐rich 1,2‐dihalobenzenes. A wide variety of thiophene derivatives bearing useful functions such as formyl, acetyl, cyclopropylmethanone, 2‐methyl‐1,3‐dioxolane, ester, nitrile or chloro was tolerated allowing to prepare poly‐functionalized 2′‐aryl‐2,3′‐bithiophenes. Moreover, this one pot preparation of 2′‐aryl‐2,3′‐bithiophenes employs a low loading of an air stable commercially available palladium source associated to an inexpensive base.magnified image