The reaction between 2-aminoethylbenzene and an alkanoyl halide in the presence of pyridine forms an amide. The amide is converted to the Vilsmeier electrophile by reaction with phosphorous oxytrichloride. The cyclization is produced by attack of the benzene to said electrophile. A final oxidation generates isoquinoline.

bischer napieralski synthesis 01


bischer napieralski synthesis 02

[1] Nucleophilic addition to acid halide
[2] Elimination of hydrogen chloride
[3] Attack phosphorus oxytrichloride
[4] Cyclization by attack of benzene on the electrophile
[5] Recovery of aromaticity.
[6] Delete
[7] Oxidation