Transition-Metal-Free Boryl Substitution Using Silylboranes and Alkoxy Bases

Silylboranes are used as borylation reagents for organohalides in the presence of alkoxy bases without transition-metal catalysts. PhMe ₂ Si-B(pin) reacts with a variety of aryl, alkenyl, and alkyl halides, including sterically hindered examples, to provide the corresponding organoboronates in good yields with high borylation/silylation ratios, showing good functional group compatibility. Halogenophilic attack of a silyl nucleophile on organohalides, and subsequent nucleophilic attack on the boron electrophile are identified to be crucial, based on the results of extensive theoretical and experimental studies. This borylation reaction is further applied to the first direct dimesitylboryl (BMes ₂) substitution of aryl halides using Ph ₂ MeSi-BMes ₂ and Na(O- t -Bu), affording aryldimesitylboranes, which are regarded as an important class of compounds for organic materials. 1 Introduction 2 Boryl Substitution of Organohalides with PhMe ₂ Si-B(pin)/Alkoxy Bases 3 Mechanistic Investigations 4 DFT Mechanistic Studies Using an Artificial Force Induced Reaction (AFIR) Method 5 Dimesitylboryl Substitution of Aryl Halides with Ph ₂ MeSi-BMes ₂ /Na(O- t -Bu) 6 Conclusion.