Fluoroboric acid adsorbed on silica-gel (HBF4-SiO2) as a new, highly efficient and reusable heterogeneous catalyst for thia-Michael addition to α,β-unsaturated carbonyl compounds

HBF4-SiO2 efficiently catalyses the thia-Michael addition to α,β-unsaturated carbonyl compounds and finds application in the one-pot synthesis of 2,3-dihydro-1,5-benzothiazepines.