Synthesis of 2‐Fluoropyrroles via [4 + 1] Cycloaddition of α,β‐Unsaturated Imines with In Situ‐Generated Difluorocarbene

Abstract

2‐Fluoropyrroles are synthesized via the [4 + 1] cycloaddition of α,β‐unsaturated imines with difluorocarbene (:CF2), which is generated in situ from trimethylsilyl 2,2‐difluoro‐2‐(fluorosulfonyl)acetate (TFDA). The α,β‐unsaturated imines are treated with TFDA in the presence of a Proton Sponge catalyst, facilitating the catalytic generation of: CF2. The resulting carbene underwent [4 + 1] cycloaddition with imines through azomethine ylide intermediates, yielding 5,5‐difluoropyrrolines. Subsequent dehydrofluorination with 1,8‐diazabicyclo[5.4.0]‐7‐undecene produced the targeted 2‐fluoropyrroles.