Enediynes from aza-enediynes: C,N-dialkynyl imines undergo both aza-Bergman rearrangement and conversion to enediynes and fumaronitriles

reaction; see text] Aza-enediynes (C,N-dialkynyl imines) undergo thermal aza-Bergman rearrangement to beta-alkynyl acrylonitriles through 2,5-didehydropyridine (2,5-ddp) intermediates. Certain aza-enediynes also undergo an alternative process affording enediynes and fumaronitriles. Studies employing a specifically (l3)C-labeled aza-enediyne show that the conversion to enediyne is second order in aza-enediyne, proceeds by a "head-to-tail" coupling, and affords the (Z)-enediyne.