Thiocarbonyl fluoride generated in situ from difluorocarbene for cyclization of vicinal X-H substituted amines (X = N, O or S)

Abstract

Difluorocarbene has served as a versatile intermediate in organic synthesis. The transformation of difluorocarbene into thiocarbonyl fluoride, which was discovered by us previously, can be developed as a synthetic tool for the cyclization of vicinal X-H substituted amines to provide various five-membered heterocycles. However, aryl amines are required to be used and difluoromethylation of the NH bond or a newly generated S-H bond cannot be suppressed. Herein we describe the use of thiocarbonyl fluoride generated in situ as a thiocarbonyl source for the cyclization of vicinal X-H substituted alkyl amines (X = N, O, S) to provide imidazolidine-2-thiones, oxazolidine-2-thiones and thiazolidine-2-thiones. The use of alkyl amines constructs different heterocycles with those obtained from aryl amines. The free NH bond remains intact without being difluoromethylated.