The acid-free, organocatalytic acetalization of various aldehydes and ketones with N, N′- bis [3, 5-bis (trifluoromethyl) phenyl] thiourea is presented. The neutral, double hydrogen bonding thiourea catalyst can be used at very low loadings of 0.01–1mol% at room temperature to furnish the respective acetals in 65–99% yield at turnover frequencies around 600h− 1. Acid-labile TBDMS-protected as well as unsaturated aldehydes can be ...
