Derivatization of an Alkylideneborane with B═C Bond Cleavage.

We present the synthesis, structural characterization, and reactivity of alkylideneborane 2 , supported by π-donating N-heterocyclic imino and σ-donating N-heterocyclic carbene (NHC) ligands. The incorporation of these ligands effectively weakens the B═C bond strength, leading to enhanced reactivity. Consequently, selective cleavage of the B═C bond can be achieved using pyridine- N -oxide, sulfur, and selenium, resulting in the formation of 1,3-dioxa-2,4-diboretane 3 , thioxoborane 4 , and selenoborane 5 , respectively. Furthermore, intriguing B═C bond insertions with CO 2 and CS 2 are observed, affording zwitterionic borenium/fluorenide 6 and dithiaboretane 7 . The former species 6 is readily converted to transient oxoborane and imidazolium enolate, showcasing the bora-Wittig reaction of alkylideneborane. This investigation highlights the potential of alkylideneborane as a versatile building block for synthesizing novel organoboron compounds through unconventional transformations.