A BH Borenium-Derived Thioxoborane, Its Persulfide, and Their Li-Induced Reactions with Alkynes and with Carbon Dioxide.

Insertion of sulfur into the B-H bond of the BH borenium salt [IMes(CF)BH] followed by deprotonation gave the thioxoborane IMes(CF)B═S. Subsequent treatment with additional sulfur gave the corresponding boron persulfide, a NHC-stabilized boradithiirane. The B═S compound reacted with carbon dioxide in the presence of the lithium salt Li[B(CF)] by formal [2+2] cycloaddition to give a boron thiocarbonate-type product. The boron persulfide formally inserted phenyl acetylene into the B-S bond in the presence of Li[B(CF)] to give the respective five-membered heterocycle.