Competitive [4 + 2]-Cycloaddition versus [1,5]-Hydrogen Sigmatropy in a Cycloheptatriene. An Efficient Route to 3-Azatricyclo[5.3.1.0^4,10]undeca-5,8-diene

Thermal rearrangements of N-acyl-7-aminocyclohepta-1,3,5-trienes 7b-e in octane or xylene provide [4 + 2]-cycloaddition products 8b-e and [1,5]-hydrogen sigmatropic rearrangement products 9b-e. The relative rate of formation for 8e/9e is 1.5 in refluxing octane. At a higher reaction temperature in xylene and longer reaction times, 7b afforded a second hydrogen-shift product 10b. No thermal [3,3]-carbon shift products were observed from IV-allyl cycloheptatrienes 9b-e or 10b in octane or xylene. The thermal behavior of 7b-e can be contrasted with that of O-allyl cyclohepta-1,3,5-triene 1.