A New Class of Substrates for Nucleophilic 5‐endo‐trig Cyclization, 2‐Trifluoromethyl‐1‐alkenes: Synthesis of Five‐Membered Hetero‐ and Carbocycles That Bear Fluorinated One‐Carbon Units

Disfavored 5-endo-trig cyclizations were achieved in 2-trifluoromethyl-1-alkenes with a nucleophilic nitrogen, oxygen, sulfur, or carbon atom through 1) intramolecular S(N)2' reaction with loss of a fluoride ion or 2) intramolecular nucleophilic addition to the vinylic group. This reaction manifold provides a versatile method for the synthesis of indolines, indoles, pyrrolidines, tetrahydrofurans, 2,3-dihydrobenzo[b]thiophenes, tetrahydrothiophenes, and cyclopentanes that bear a fluorinated one-carbon unit such as a difluoromethylene, difluoromethyl, or trifluoromethyl group.