Highly Colored Boron-Doped Thiazolothiazoles from the Reductive Dimerization of Boron Isothiocyanates.

Reduction of (CAAC)BBr2(NCS) (CAAC = cyclic alkyl(amino)carbene) in the presence of a Lewis base L yields tricoordinate (CAAC)LB(NCS) borylenes which undergo reversible E / Z -isomerization. The same reduction in the absence of L yields deep blue, bis(CAAC)-stabilized, boron-doped aromatic thiazolothiazoles resulting from the dimerization of dicoordinate (CAAC)B(NCS) borylene intermediates.