Non-electrophilic behaviour of alkyl-substituted metaphosphates in the gas phase: formation of alkenes by an unusual 1,2-methyl shift induced by hydrogen abstraction–a methyl analogue of the neophyl ester rearrangement

Pyrolytic expulsion of ethylene from 2-neopentoxy-1,3,2-dioxaphospholane in the gas phase yields a virtually quantitative mixture of 2-methylbut-1-ene and its more stable isomer, 2-methylbut-2-ene in the ratio 2 : 1; this can be rationalised, using deuterium-labelling studies, as being formed from a thermally generated metaphosphate by a cyclic, concerted elimination reaction involving, as the key step, an unusual 1,2-methyl shift induced by competing α- and γ-hydrogen abstraction reactions with loss of metaphosphoric acid.