Photocatalyzed regioselective hydrosilylation for the divergent synthesis of geminal and vicinal borosilanes

Abstract

Geminal and vicinal borosilanes are useful building blocks in synthetic chemistry and material science. Hydrosilylation/hydroborylation of unsaturated systems offer expedient access to these motifs. In contrast to the well-established transition-metal-catalyzed methods, radical approaches are rarely explored. Herein we report the synthesis of geminal borosilanes from α-selective hydrosilylation of alkenyl boronates via photoinduced hydrogen atom transfer (HAT) catalysis. Mechanistic studies implicate that the α-selectivity originates from a kinetically favored radical addition and an energetically favored HAT process. We further demonstrate selective synthesis of vicinal borosilanes through hydrosilylation of allyl boronates via 1,2-boron radical migration. These strategies exhibit broad scopes across primary, secondary, and tertiary silanes and various boron compounds. The synthetic utility is evidenced by access to multi-borosilanes in a diverse fashion and scaling up by continuous-flow synthesis.

Photo-Triggered, Copper(II) Chloride-Catalyzed Radical Hydroalkylation and Hydrosilylation of Vinylboronic Esters To Access Alkylboronic Esters

“…Organosilicon compounds hold immense significance in organic synthesis as they serve as valuable reagents, bioactive components, and find applications in functional materials . Inspired by previous photomediated hydrosilylation reactions of alkenes with silane via Si–H activation, we then turned our attention to explore the substrate scope of the hydrosilylation reaction of vinylboronic esters with respect to silanes (Table B). Pleasingly, trialkyl silanes with multifarious-sized alkyl groups were compatible well, giving the corresponding products ( 12 – 15 ) in moderate to good yields.…”

Nickel/photoredox-catalyzed three-component silylacylation of acrylates via chlorine photoelimination

“…2 a , b Such strategies have been significantly advanced by recent innovations in photoredox chemistry ( Scheme 1b , right). 10 These advancements provide a mild and efficient strategy for generating silyl radicals. Nonetheless, the field continues to face notable obstacles in realizing efficient 1,2-silyldifunctionalization with complex silyl groups, primarily due to the requirement for an external HAT reagent and the necessity for its meticulous integration with photoredox catalysis.…”

Silylation and (Hetero)aryl/alkenylation of Unactivated Alkenes via Radical-Mediated Distal 1,4-Migration with Hydrosilanes under Organophotocatalysis

“…Another manner of hydrosilylation of alkenes with hydrosilanes used Lewis acids as catalysts, which shows good reactivity and selectivity toward electron-rich alkenes (Scheme b) . In addition, photoredox hydrosilylation of alkenes with hydrosilanes could also afford useful organosilicon compounds (Scheme c). , Although intensive efforts in this research field have been made, the current strategy is often limited to hydrosilylation of an alkene for the construction of one carbon–silicon bond. There are few reports for the simultaneous incorporation of carbon–silicon and carbon–carbon bonds to alkenes, which could increase diversity and complexity of organosilicon compounds bearing multiple functional groups .…”