retro-Cheletropic ene reactions with 2-carbena-1,3-dioxolane as chelefuge

N[β-(Hetero)arylvinyl] ketenimines and carbodiimides bearing adequately positioned 1,3-dioxolane functions experience a new class of tandem process consisting of a 6π electrocyclic ring closure followed by a rare retro-cheletropic ene reaction, the extrusion of 2-carbena-1,3-dioxolane. This mechanistic sequence is supported by a computational study using DFT methods, showing that the simultaneous recovery of aromaticity at two rings is the clue for the low energy barrier of the retro-cheletropic step. Moreover, the highly exergonic decomposition of 2-carbena-1,3-dioxolane into CO2 plus ethylene contribute to the success of the tandem sequences.