1-Phenylsulfanyl-2,2,2-trifluoroethyl isocyanide (2a) readily and selectively trimerized to 4,6-bis(phenylsulfanyl)-1- (1-phenylsulfanyl-2,2,2-trifluoroethyl)-5-(2,2,2- trifluoroethylideneamino)-2-trifluoromethyl-1,2-dihydropyrimidine (5) at room temperature, while other alpha-phenylsulfanyl isocyanides such as phenyl(phenylsulfanyl)methyl isocyanide (2b) are stable. Heating of 2b resulted in formation of the corresponding nitrile as well as diphenyl disulfide and [bis(phenylsulfanyl)methyl]benzene.