Palladium‐Catalyzed Cascade Heck Coupling and Allylboration of Iododiboron Compounds via Diboryl Radicals

• Published in: Angewandte Chemie International Edition 2024-04, Vol.63 (18), p.e202401050-n/a
• Main Authors: Wei, Yi, Xie, Xiao‐Yu, Liu, Jiabin, Liu, Xiaoxiao, Zhang, Bo, Chen, Xin‐Yi, Li, Shi‐Jun, Lan, Yu, Hong, Kai
• Format: Article
• Language: English
• Subjects: Aldehydes; Ambiphilic Reagent; Boron; Cascade chemical reactions; Cross coupling; Functional groups; Imines; Intermediates; Iododiboron; Multicomponent Reaction; Nucleophiles; Organic chemistry; Organoboron; Palladium; Stereoselectivity; Synthetic Methods
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202401050

Geminal bis(boronates) are versatile synthetic building blocks in organic chemistry. The fact that they predominantly serve as nucleophiles in the previous reports, however, has restrained their synthetic potential. Herein we disclose the ambiphilic reactivity of α‐halogenated geminal bis(boronates), of which the first catalytic utilization was accomplished by merging a formal Heck cross‐coupling with a highly diastereoselective allylboration of aldehydes or imines, providing a new avenue for rapid assembly of polyfunctionalized boron‐containing compounds. We demonstrated that this cascade reaction is highly efficient and compatible with various functional groups, and a wide range of heterocycles. In contrast to a classical Pd(0/II) scenario, mechanistic experiments and DFT calculations have provided strong evidence for a catalytic cycle involving Pd(I)/diboryl carbon radical intermediates. The ambiphilic reactivity of iododiboron compounds was disclosed by palladium‐catalyzed three‐component reactions of iododiborons, alkenes and aldehydes/imines. The reaction features mild conditions, broad scope, excellent diastereoselectivity and functional group tolerance. An unconventional Pd(0/I/II) catalytic cycle is operative, supported by mechanistic experiments and DFT calculations.