Synthesis of Tetrasubstituted 2-Aryl-3-arylsulfonyl Pyrroles: Unexpected Regioselectivity in Directed ortho-Metallation Reactions

Abstract

3-Arylsulfonyl pyrroles can be readily obtained from 3-Br-TIPS pyrrole via halogen-metal exchange and subsequent sulfonylation. The regioselectivity of the subsequent directed ortho-metallation (DOM) reaction in order to functionalise the C-2 position depends on the nature of the base (LTMP, n-or s-BuLi) and the Nsubstituent (SEM or Boc) used. The bulk of the N-substituent also strongly influences the yield of the subsequent Suzuki coupling with 2-iodo-3-arylsulfonyl pyrrole derivatives.