Useful Organocatalyst for Acid-free Acetalization

Schreiner et al. have reported the acetalization reaction using 1,3-bis[3,5-bis(trifluoromethyl)phenyl]thiourea (1) as a catalyst. Acidic catalysts, such as p-toluenesulfonic acid, are generally needed for acetalization. However, the use of 1 makes it possible to acetalize carbonyl compounds under neutral conditions, affording the corresponding acetal compounds in moderate to high yields.

In particular, 1 is useful for acetalization of carbonyl compounds bearing acid-sensitive groups, such as the TBDMS protecting group.