Utility and NMR studies of alpha,beta-unsaturated acylammonium salts: synthesis of polycyclic dihydropyranones and a dihydropyridone

摘要

Organocatalyzed, tandem Michael-lactonizations and a lactamization employing cyclic 1,3-dicarbonyl and an enamino ketone, respectively, were achieved through the intermediacy of alpha,beta-unsaturated acylammonium salts derived from commodity acid chlorides or in situ generated enol esters. 4-Dimethylaminopyridine (DMAP) promotes this process providing the corresponding polycyclic dihydropyranones and a dihydropyridone in good yields. The utility of this methodology was demonstrated in the formal synthesis of the alkaloid dielsine and the anticoagulant warfarin. Comparative C-13 NMR studies of acylammonium salt intermediates provide insights into the impact of their formation on the reactivity of the beta-carbon. (C) 2015 Elsevier Ltd. All rights reserved.