The role of the carbonyl group in the intermolecular 1,3-cycloaddition of azido(2-heteroaryl)methanones with activated olefins

Abstract

Treatment of the azido(2-heteroaryl)methanones 1–5 with methyl (E)-3-pyrrolidinoprop-2-enoate at room temperature yielded the methyl 1,2,3-triazolecarboxylate 6 and (2-heteroaryl) (pyrrolidino)methanones 1a–5avia an unusual 1,3-cycloaddition reaction. Analogous reactions of the azidomethanones 1 and 2 with the dipolarophiles methyl crotonate, methyl propiolate or methyl but-2-ynoate failed. In contrast, the strained 5-methylenebicyclo[2.2.1]hept-2-ene reacted smoothly with the carbonyl azides 1–5 to give triazoline adducts which subsequently formed the (2-heteroaryl)(6-methylene-3-azatricyclo[3.2.1.0]octan-3-yl)methanones 1b–5b by loss of molecular nitrogen.