Bisphosphane-Stabilized Borylenes: Unlocking Borylene Transfer Reactivities.

The development of borylene-transfer reactions-a powerful yet underdeveloped strategy for the efficient construction of boron-containing compounds-has been hindered by the scarcity of reliable reagents. A fundamental challenge lies in balancing the high ambiphilic reactivity required for transfer with the requisite molecular stability. Herein, we report the synthesis of a series of bisphosphane-stabilized borylenes and disclose their exceptional borylene-transfer capabilities. The target borylenes (3) were prepared via facile deprotonation of the corresponding bisphosphane-coordinated hydroboronium precursors using KHMDS (potassium bis(trimethylsilyl)amide). Notably, borylene 3a undergoes formal B─H bond insertion with hydroboranes to yield diborane (6) derivatives. Furthermore, 3a facilitates unprecedented borylene transfer to polar π systems, including benzaldehyde and chalcone, providing efficient access to three-membered oxaboriranes and boriranes. Experimental and computational studies reveal that the labile phosphorus-boron (P-B) coordination is pivotal in maintaining the high borylene-transfer capability of 3a. These preliminary results set the stage for the use of stable hydroboronium compounds as practical borylene-transfer reagent precursors in synthetic chemistry.