Formation of a pyridine ring fused to two octahydroacridine units

Formation of a pyridine ring fused to two octahydroacridine units 

Protocol 6 involves heating Mannich compound 10 in DMSO, apparently causing elimination of dimethylamine and formation of enone 20 as a reactive intermediate. The corresponding enone has been synthesized in the 9-butyl series,6,22 but comparable yields are obtained in pyridine cyclization reactions involving either the preformed enone or the Mannich HQ salt.7 Prior to addition of 10, ketone 9 is heated with ammonium chloride in DMSO to promote the formation of imine 21. Isomerization of this imine to the enamine tautomer 22, Michael addition of this nucleophile to enone 20, and elimination of water account for the formation of product 11. Like many polycyclic terpyridyl analogues, this product is sparingly soluble in DMSO and is readily isolated by filtration of the reaction mixture. 

Caution) Carry out all procedures in a well-ventilated hood, and wear disposable vinyl or latex gloves and chemical-resistant safety goggles. 

Dry the round-bottomed flask and stirrer bar in an electric oven (110°C, 2 h). 

Add the 5-benzylidene-2,3,5,6,7,8-hexahydroacridin-4(1 W)-one,/V,A/-dimethyl-(methylene)ammonium chloride, and acetonitrile to the flask. Stir the reaction mixture at room temperature under N2 for 36 h. 

---