Stereoconvergent access to Z-allylborons from E/Z-mixed 1,3-dienes via Cu-guanidine catalysis

• Main Authors: Zhang, Ai, Zhang, Huangfeng, Jin, Tao, Ge, Lin, Ma, Xiaoyan, Tang, Jinghua, Liu, Jinyu, Tan, Choon-Hong, Lee, Richmond, Ge, Yicen
• Other Authors: School of Chemistry, Chemical Engineering and Biotechnology
• Format: Article
• Language: English
• Published: 2025
• Subjects: Chemistry; Protoborylation; Stereoconvergency
• Online Access: https://hdl.handle.net/10356/182257
• Institution: Nanyang Technological University

Merging the stereoisomeric mixture of substrate into a single product through stereospecific transformation is a challenging but higher-order synthetic strategy, which perfectly meets the demand of cost control in the precise chemical production. In this work, the stereoconvergent synthesis of Z-allylic boronates was realized with protoborylation of E/Z-mixed 1,3-dienes catalyzed by a novel copper-guanidine complex. The reaction could proceed smoothly under very mild conditions with good functional group tolerance, and convert diverse aryl-substituted 1,3-dienes into the desired Z-1,4-addition products with excellent chemo-, regio-, and stereoselectivities in minutes. Detailed mechanistic studies also helped to disclose the origin of stereoconvergency. Both E- and Z-diene were found directly undergoing a rapid borylation without E/Z isomerization of C=C bond, followed by a convergent formation of the same thermodynamically stable allylcopper intermediate before the slow protonation step occurred.