p-Toluenesulfonic acid → 4-Nitrobenzoxazole

Participants

Reaction Steps

Compounds of Formula I also can be prepared as illustrated by exemplary reaction in Scheme 3. Reaction of 2-amino-3-nitro-phenol and triethyl orthformate in the presence of a acid such as p-toluenesulfonic acid produced 4-nitrobenzooxazole. The nitro group was reduced to give the 4-amino-benzooxazole, which was converted to the methylamino-benzooxazole in two steps. Treatment of the compound with base, such as sodium ethoxide converted the 4-methylamino-benzooxazole into a 4-hydroxy-1-methylbenzimidazole. Reaction of 4-hydroxy-1-methylbenzimidazole with an aryl-aldehyde such as 5-bromoveratraldehyde and malononitrile in the presence of a base, such as piperidine produced the substituted 7-methyl-imidazo[4,5-h]chromene.

Provenance & Evidence