Hafnium Trifluoromethanesulfonate (Hafnium Triflate) as a Highly Efficient Catalyst for Chemoselective Thioacetalization and Transthioacetalization of Carbonyl Compounds

A range of carbonyl compounds including aliphatic and aromatic aldehydes and ketones were converted to the corresponding thioacetals in high yields in the presence of a catalytic amount of hafnium trifluoromethanesulfonate (0.1 mol %, room temperature), The mild conditions tolerated various sensitive functional and protecting groups and were racemization-free when applied to alpha-aminoaldehydes. Transacetalization and chemoselective thioacetalization of aromatic aldehydes in the presence of aliphatic aldehydes and ketones were also documented.