1. Center for Natural Sciences, College of Liberal Arts and Sciences, Kitasato University, 1‐15‐1, Kitasato, Sagamihara‐shi, Kanagawa‐ken 228‐8555, Japan;2. School of Pharmacy, Iwaki Meisei University, 5‐5‐1, Iino, Chuodai, Iwaki‐shi 970‐8551, Japan
Abstract:
Fused tetracycles, 6‐alkyl‐3‐alkoxy‐2‐cyano‐4,5,6a,11‐tetraazabenzo[a]fluorene derivatives ( 5a , b , c , d , e , f ), are synthesized from 2‐alkoxy‐5‐(benzimidazol‐2‐ylidene)‐3‐cyano‐6‐imino‐5,6‐dihydro‐pyridines ( 4b , c ), and when refluxed in ethyl orthoacetate or ethyl orthopropionate, the elecrophilic aromatic substitution occurs at the ortho position of the cyanopyridine ring in the fused tetracycles ( 5b , c , e , f ) to afford 6‐alkyl‐3‐alkoxy‐2‐cyano‐1‐ethyl‐4,5,6a,11‐tetraazabenzo[a]fluorenes( 6b , c , e , f ).
