Heat pyrolysis of the oxazines formed from 2-piperidineethanol produced 2, 3- dehydropiperidine enamines. The same results were observed when these oxazines were irradiated with microwaves. Various 2-substituted perhydrooxazines were synthesized by allowing 2-piperidineethanol or 2-piperidinemethanol to react with aldehydes or ketones.