Novel syntheses of some new 3,4-dihydrospiro{benzimidazo[1,2-a]pyridine-3,3′-indolin}-2′-one derivatives

2-Methylbenzimidazole 1 reacted with 3-dicyanomethylidine-1-ethyl-2-oxoindoline 2 in ethyl acetate to afford 1-amino-2-cyano-3,4-dihydro-1'-ethylspiro{benzimidazo[1,2-a]pyridine-3,3'-indolin}-2'-one 6, which was used as a key intermediate in the synthesis of fused spiropolyheterocyclic derivatives of benzimidazopyridopyrimidine and/or benzimidazonaphthyridine nucleus incorporating an indoline moiety.