Synthesis of O-2-(acyl)vinylketoximes and their unusual rearrangements into 2-and 3-acyl-substituted pyrroles

O-2-(Acyl)vinylketoximes (freshly prepared from ketoximes and acylacetylenes in the presence of Ph3P as catalyst in up to 83% yields) rearrange upon heating (125-150 degrees C) to give 2- or 3-acylpyrroles, wherein the positions of the acyl substituents do not correspond to known O-vinyloxime rearrangements: the chemo- and regioselectivity of the rearrangements depend on the reaction conditions. The described rearrangement enables syntheses of previously inaccessible substituted 2- or 3-acylpyrroles. (C) 2010 Elsevier Ltd. All rights reserved.