trimethylsilylmethyl isothiocyanate with aldehydes or ketones afforded oxazolidine-2-thione derivatives, which involves the isothiocyanato carbanion as an intermediate. Imidazolidine-2-thiones were similarly prepared from imines. The reaction of bis(trimethylsilyl)methyl isothiocyanate with benzaldehyde in the presence of a catalytic amount of n-Bu4NF gave styryl isothiocyanate and 5-phenyl-4-trimethylsilyloxazolidine-2-thione