Not antiaromaticity gain, but increased asynchronicity enhances the Diels-Alder reactivity of tropone.

Tropone is an unreactive diene in normal electron demand Diels-Alder reactions, but it can be activated via carbonyl umpolung by using hydrazone ion analogs. Recently, the higher reactivity of hydrazone ion analogs was ascribed to a raised HOMO energy induced by antiaromaticity (L. J. Karas, A. T. Campbell, I. V. Alabugin and J. I. Wu, Org . Lett ., 2020, 22 , 7083). We show that this is incorrect, and that the activation barrier is lowered by increased asynchronicity.