Highly efficient and cis-selective carbofunctionalization of internal alkynes catalyzed by palladium a-diimine complexes

Herein, a novel palladium α-diimine complex, in which two bulky tert-butyl substituents were incorporated into the acenaphthyl backbone of diimine, catalyzed carbofunctionalization of internal aklynes protocol has been established for the highly regio- and stereo-selective synthesis of cis-type tetraarylethylenes (TAEs). The structure-activity relationship of the catalyst structures and their catalytic properties was also well investigated. The experimental results demonstrated that introducing of two bulky substituents into the conjugated acenaphthyl framework of the diimine is the crucial reason for the excellent reactivities and cis-selectivities. It not only delivered the desired cis-TAE products in up to 50:1 cis/trans isomeric ratio and significantly expanded the substrate scope, including the electron-deficient aryl halides and substrates with bulky substitutions, to streamline the synthesis of cis-TAEs, which had been challenging to prepare according to the conventional carbo-metalation methods.