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(C6F5)BH]+ followed by deprotonation gave the thioxoborane IMes(C6F5)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(C6F5)4] 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(C6F5)4] to give the respective five-membered heterocycle.