Hafnium Trifluoromethanesulfonate (Hafnium Triflate) as a Highly Efficient Catalyst for Chemoselective Thioacetalization and Transthioacetalization of Carbonyl Compounds
摘要:
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.
In the presence of gallium chloride, dithioacetals reacted with allylstannanes to give the corresponding homoallyl sulfides in high yields. The present method could be applied to the chemoselective allylation of bis(dithioacetal) of keto aldehyde, and the dithioacetal arising from keto function reacted with allylstannane exclusively.
Phosphorus pentoxide supported on silica gel (P2O5/SiO2) efficiently acts as a highly active and reusable catalyst for cyclic and non-cyclic S,S-acetalization of a variety of carbonyl compounds under mild, solvent-free and ambient conditions. This method offers significant advantages such as high conversion, clean work-up, short reaction times and simplicity in operation.[GRAPHICS].
SAIGO, KAZUHIKO;HASHIMOTO, YUKIHIKO;KIHARA, NOBUHIRO;HARA, KEN-ICHI;HASEG+, CHEM. LETT.,(1990) N, C. 1097-1100