Cycloaddition behaviour of pyrazol-4-one N,N-dioxides toward unsaturated compounds. Stereochemical and mechanistic aspect

Abstract

The Cycloaddition behaviour of 2,5-disubstituted pyrazol-4-one N,N-dioxide 1a-c toward various unsaturated compounds 2 was investigated. The structures of the products were determined on the basis of the 1H and 13C NMR spectral data together with the X-ray crystallographic data. In general, the predominant formation of the exo 1,3-dipolar cycloadducts was observed. The cycloaddition behaviour of 1a-c toward 2 is discussed on the basis of the kinetic and computational data.