Preparation of New Nitrogen-Bridged Heterocycles. XIII. : Syntheses of Some Tricyclic and Tetracyclic Indolizine Derivatives with Antiallergic Activity

Abstract

Alkaline treatment of 2, 3-annelated 1-ethoxycarbonylmethylpyridinium bromides was investigated as a method for the preparation of 1, 8-annelated indolizine derivatives. The reaction of 1-ethoxycarbonylmethyl-2, 3-cyclopentenopyridinium bromide (1) with ethanolic sodium ethoxide did not afford any significant products, but similar treatment of 1-ethoxycarbonylmethyl-2, 3-cyclohexenopyridinium bromide (8) gave the expected 1, 8-annelated 2(3H)-indolizinone, 8, 9-dihydro-7H-pyrrolo[3, 2, 1-ij]quinolin-1(2H)-one (9), in 53% yield. The reactions of the salt 8 with a base in the presence of some vinylating and alkylating or acylating agents afforded the corresponding 1-alkoxy- or 1-acyloxy-2-vinylpyrroloquinoline derivatives (26-35), which were further transformed to tetracyclic indolizines fused with a furan or a puran ring. Some of these tricyclic and tetracyclic indolizines showed antiallergic activity.