The regioselectivity in the reactions of <i>N</i>‐aryl‐<i>C</i>‐ethoxycarbonylnitrilimines with acrylic acid derivatives

Abstract

Abstract The cycloaddition of a series of C ‐ethoxycarbonyl‐ N ‐arylnitrilimines 5a‐f to acrylic acid derivatives namely acrylamide, acrylonitrile and ethyl acrylate has been studied. Under thermal conditions 1,3‐dipolar cycloadditions proceed with complete regioselectivity to give 5‐R substituted 2‐pyrazolines 8–10 in high yield. The structures of the cycloadducts 8–10 were confirmed by 13 C nmr, 1 H nmr and ir spectra. The regioselectivity is interpreted in terms of HOMO(nitrilimine)‐LUMO(dipolarophile) interaction.