Base catalysed syntheses of the novel tetrahydropyridine-2-thione, piperidine-2-thione and 6-aza-2-oxa-3-oxo-5-thioxobicyclo[2.2.2]octane ring systems

Abstract

In contrast to the acid catalysed condensations of 2-ethoxycarbonylthioamides with α,β-unsaturated ketones to dihydrothiazines, base catalysis yields 6-hydroxypiperidine-2-thiones; which can be dehydrated to tetrahydropyridine-2-thiones and, if the second substituent at the 6-position is electron releasing, the molecule can eliminate ethanol transannularly to give novel lactone bridged bicyclic systems.