Uwe Beifuss and Michael Taraschewski
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.