1,3-Dipolar cycloadditions to nitrogen-substituted allenes

Abstract

A series of nitrogen-substituted allenes(2a–h) was treated with 3,5-dichloro-2,4,6-trimethylbenzonitrile oxide (4) in boiling tetrachloromethane. The reaction occurred predominantly (or exclusively) at the α,β double bond. Regardless of the site of cycloaddition, the carbon of the nitrile oxide bonded selectively to the central carbon of the allene. 4-Methylene-4,5-dihydroisoxazole monoadducts (5) reacted further to form spiro-diadducts. The stereochemistry of one diadduct was determined by X-ray diffraction analysis.