Studies on bi-heterocyclic compounds. II. 5-substituted thiazolones

Reactions of 4-methyl-2(3H)-thiazolones (5) with various N-alkoxycarbonyl pyridinium salts (6a--f) led to (N-alkoxycarbonyl dihydropyridyl)thiazolones (7a--f), oxidation of which yielded a new class of 5-pyridylthiazolones (8a--f). These reactions were applied to the synthesis of other azaarylthiazolones. Some of these azaarylthiazolones, particularly 5-(4-pyridyl)thiazolones (8b, c) and 5-(4-quinolyl)thiazolones (14a,b), showed positive inotropic activity with little chronotropic effect on guinea pig left atria.