NEW FINDINGS IN BISCHLER-NAPIERALSKI REACTION: FORMATION OF 12-AZONIANAPHTHAZULENES FROM 2-ARYL-1-NAPHTHYLFORMAMIDES AND THEIR UNEXPECTED TRANSFORMATION INTO BENZINDOLES THROUGH HYDRIDE REDUCTION

Article abstract of DOI:10.1016/0040-4039(95)00399-W

The Bischler-Napieralski Reaction (BNR) of N-<2-(2-alkoxy-4,5-methylenedioxyphenyl)-1-naphthyl>-N-methylformamides using POCl3 abnormally gave 12-azonianaphth<1.2-b>azulene derivatives, which could be effectively transformed into benzindoles with a 1-alkoxy-8-oxabicyclo<3.2.1>oct-2-ene skeleton through hydride reduction, as additional cyclized products.In contrast, the BNR of naphthylformamides with methoxy groups in place of a methylenedioxy function at the same position in the phenyl ring led to normal cyclization to give benzophenanthridinium chlorides quantitatively.The speculative mechanism for the abnormal BNR and the indole formation will be discussed.