Mass spectrometric studies. IX. Benzylidenemalonic esters and related compounds

Abstract

Skeletal rearrangements resulting from alkoxy-group migrations are prominent in the mass spectra of some benzylidenemalonic esters, and involve elimination of C₃O₂ as a neutral fragment. Similar rearrangements of a chloride atom dominate the mass spectra of benzylidenemalonyl chloride, but migrations of alkyl and aryl groups are unimportant in the mass spectra of structurally related benzylidene β-diketones. The rearrangements observed have been rationalized as the result of a four-centre migration to a carbonium ion centre.