p-Toluenesulfonic acid → 4-Nitrobenzoxazole
Reaction equation
[NH2:1][C:2]1[C:7]([N+:8]([O-:10])=[O:9])=[CH:6][CH:5]=[CH:4][C:3]=1[OH:11].[C:12]1(C)C=CC(S(O)(=O)=O)=CC=1>>[N+:8]([C:7]1[C:2]2[N:1]=[CH:12][O:11][C:3]=2[CH:4]=[CH:5][CH:6]=1)([O-:10])=[O:9]Participants
3
Procedure
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.
Workup
- customCompounds of Formula I also can be prepared
- customas illustrated by exemplary reaction in Scheme 3
Sources & evidence
- ORD record
- ord-737a81b662f14cd4b3c93fb71816d133
- Source dataset
- uspto-grants-2009_05
- Patent number
- US07528164B2
Reaction notes
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