Reaction of acetophenone and benzylphenylketone oximes with phenylacetylene: synthesis of di- and triphenylpyrroles

Abstract

The reaction of oximes of aromatic ketones with phenylacetylene in the presence of superbase systems (MOH-DMSO, where M = Li, Na, K) has been extensively studied for the first time. The effects of alkaline metal cation, the ketoximes structure and the reaction conditions (temperature, duration) on the products composition have been evaluated. Acetophenone oxime reacts with phenylacetylene (МОН-DMSO, where M = Li, Na, K, 140 о С, 6 h) to afford 2,5-diphenyl-1H-pyrrole in 14-18% isolated yield. The reaction of benzylphenylketoxime with phenylacetylene (LiОН-DМSО, 120 о С, 12 h) delivers 2,3,4-, 2,3,5-triphenyl-1H-pyrroles (in 17% total yield) and 2,3,4-triphenyl-1-[(Z)-2-phenylethenyl]-1H-pyrrole (7% yield).

Gold-catalysed rearrangement of O-vinyl oximes for the synthesis of highly substituted pyrroles

“…This powerful transformation is underutilised due to the harsh reaction conditions that result in poor yields and low levels of product chemo-/regioselectivity. 5 However, due to the potential of the Trofimov reaction in synthesis, catalytic variants seeking to improve the yield and selectivity whilst removing the need for strongly basic conditions have been developed. For example, earlier this year Anderson et al described an iridium-catalysed isomerisation of O-allyl oximes under reductive conditions that afforded 4-methyl-5-unsubstituted pyrroles.…”