Synthesis of naphtho[1,2‐b]‐, naphtho[2,1‐b]‐, and naphtho[2,3‐b]azepinones via proton‐induced cyclization of N‐1(2)‐naphthyl styrylacetamides

Abstract

On heating in polyphosphoric acid, N-1-naphthyl styrylacetamides undergo proton-induced intramolecular cyclization at position 2 of the naphthyl ring to provide 5-aryl-1,3,4,5-tetrahydro-2Н-naphtho[1,2-b]azepin-2-ones, while their N-2-naphthyl analogues, when similarly reacted, are cyclized at positions 1 and 3 of the naphthyl ring and at the amide nitrogen atom leading, respectively, to 1-aryl-1,2,3,5-tetrahydro-4Н-naphtho[2,1-b]azepin-4-ones, 5-aryl-1,3,4,5-tetrahydro-2Н-naphtho[2,3-b]azepin-2-ones, and 5-aryl-1-(2-naphthyl) pyrrolidin-2-ones.

Proton‐ and halogen‐induced cyclizations of 2‐(3‐butenyl)quinazolin‐4(3H)‐ones in the synthesis of pyrrolo[2,1‐b]‐ and pyrrolo[1,2‐а]quinazolinone derivatives

“…Taking into account the synthetic potential of protoninduced cyclizations (previously demonstrated by the preparation of thiazolo(imidazo)pyrimidones [86,87], benz-, naphth-, and thienoazepinones [88] through the treatment of the corresponding unsaturated substrates with sulfuric and polyphosphoric acids), we have tested a number of protic acids (HCl, CF 3 CO 2 H, H 2 SO 4 , polyphosphoric acid, CF 3 SO 3 H), so as to find the optimum conditions for the cyclization selectivity and to relate it to the nature of the substituents on the aromatic moiety of 2-homoallylquinazolin-4(3Н)-ones 1а-g.…”