A deprotonation pathway to reactive [B]CH 2 boraalkenes.

The BH compounds IMes(Ar F )BH(NTf 2 ) (Ar F : C 6 F 5 or FpXyl) were converted to the IMes(Ar F )BCH 2 boraalkenes in a three step reaction sequence of B-methylation with methyllithium, hydride abstraction and deprotonation. The BCH 2 boraalkenes reacted with elemental sulfur to give a thiaborirane product. They underwent [2+2] cycloaddition reactions with carbon dioxide or sulfur dioxide to give four-membered boron containing heterocycles. The boraalkenes added strongly Lewis acidic boranes at their CH 2 carbon atoms. The corresponding HB(C 6 F 5 ) 2 /boraalkene adduct reduced carbon monoxide to a -OCH(C 6 F 5 )- moiety inside a five-membered heterocycle at the B-CH 2 -B template. The boraalkenes reacted with the [(Me 2 S)AuCl] reagent to form the corresponding (boraalkene)AuCl complexes.