Triflic Acid-Catalyzed Tandem Reactions of Cyclopropyl Alcohols with Sulfonamides for the Synthesis of Pyrrolidines

Abstract

Intermolecular tandem reactions of substituted cyclopropyl alcohols with sulfonamides for the synthesis of pyrrolidines can be catalyzed by triflic acid (TfOH). The desired pyrrolidines were provided in yields of 16%～83% with 10 mol% catalyst loadings at 100 ℃. A variety of cyclopropyl alcohols, such as the electron-withdrawing, electron-donating and bulkyl groups on aromatics, and sulfonamide with electron-withdrawing, and electron-donating substituents, could be tolerated under the optimized reaction conditions. An inexpensive and commercially available triflic acid reagent has been shown efficient for the synthesis of pyrrolidines, which is an alternative to metal-catalyzed reactions.