General approach to 2-fluoroalkyl 1,3-azoles via the tandem ring opening and defluorinative annulation of N-fluoroalkyl-1,2,3-triazoles†
Rhodium-catalyzed transformation of N-fluoroalkyl-1,2,3-triazoles in the presence of tert-butyl carbamate or water provided an efficient route to 2-fluoroalkyl imidazoles and 2-fluoroalkyl oxazoles, respectively. The treatment of N-fluoroalkyl-1,2,3-triazoles with excess water gave fluoroalkylated ketamides which were cyclized in situ to 2-fluoroalkyl oxazoles or thiazoles. Trifluoromethyl- and other difluoroalkyl-substituted heterocycles were obtained by the present method. The mechanism of this cascade transformation involving carbene insertion, HF elimination and cyclization was proposed.