One-pot synthesis of multisubstituted propenylbenzenes from benzyl chlorides through relay catalysis of palladium.

A strategy for the synthesis of multisubstituted propenylbenzenes using benzyl chlorides as starting materials is described. The palladium-catalyzed allylative dearomatization and the subsequent Wagner-Meerwein rearrangement as well as the olefin isomerization proceeded smoothly under mild conditions to produce propenylation products in good yields with high regioselectivity. Control experiments and cyclic voltammetry analysis suggest that BuSnCl, a by-product generated in the first step of allylative dearomatization, plays an essential role in the third step of olefin isomerization in the presence of a Brønsted acid.