C(sp3)–H functionalization of N-protected dialkylpyrrole derivatives with azodicarboxylates

Abstract

A metal-free, catalytic route to the activation of C(sp³)–H bonds in N-protected dialkylpyrroles to diazodicarboxylates is reported using HB(C₆F₅)₂ as the optimized catalyst. These reactions tolerate aryl and alkyl substituents on the pyrrole N-atom as well as variation in the azodicarboxylates giving rise to 41 examples. These reactions were also performed on a gram scale and conversion to the corresponding amino-esters is demonstrated. A DFT computation study reveals that the Lewis acid adduct of azodicarboxylates generates a Lewis acidic N-atom capable of hydride abstraction from dimethylpyrrole, ultimately effecting C(sp³)–H functionalization.