Reactions between Triazolinediones and Equilibrating Forms of Cycloheptatriene Derivatives Featuring 7,7-Spiro and 1,7-Fused Heterocyclic Rings

Abstract

Nitrile oxide−azaheptafulvene adducts consist of rapidly equilibrating mixtures of fused (1) and spiro (2) isomers, the relative stabilities of which are nicely reproduced by B3LYP/ 6-31G* calculations. The reaction between these compounds and MTAD affords only two diastereomeric adducts [9 (dominant) and 10], both deriving from the reaction of MTAD with 1 even in cases in which that isomer could not be detected by NMR spectroscopy. These adducts are formal Diels−Alder