A metal-free sigmatropic rearrangement/cyclization/aromatization cascade reaction of hydroxy/aminophenyl propargyl alcohols with fluoroalkanesulfinyl chlorides: synthesis of 3-fluoroalkanesulfonyl benzofurans and indoles†

Abstract

A metal-free protocol to synthesize 2-alkyl-3-fluoroalkanesulfonyl benzofurans and indoles from o-hydroxyphenyl/o-aminophenyl propargyl alcohols or 2-propynolphenols/2-propynolanilines and fluoroalkanesulfinyl chlorides (R_FSOCl) was disclosed. The mechanism is proposed to involve a sequential [1,2]/[2,3]-sigmatropic rearrangement/intramolecular oxy-addition/1,3-H migration cascade of propargyl triflinates generated in situ via O-fluoroalkanesulfinylation of propargyl alcohols. The procedure utilizes readily available propargyl alcohols and R_FSOCl as starting materials and offers a broad substrate scope with excellent performance (55 examples, up to 98% yield).