2-Aminobuta-1,3-dienes as annulation reagents for 4-quinolones and benzothiopyran-4-ones: an attractive route for the highly diastereoselective synthesis of acridine- and thioxanthene-derivatives

Abstract

Enamines regioselectively add to the CN⁺-bond of 4-silyloxyquinolinium triflates with high yields, and the BF₃·Et₂O mediated annulations of 4-quinolones with 2-aminobuta-1,3-dienes proceed with high diastereoselectivity to give substituted 1,2,3,4,4a,9,9a,10-octahydroacridine-3,9-dione derivatives; 4-silyloxy-1-benzothiopyrylium triflates and benzothiopyran-4-ones behave analogously.