p-Toluenesulfonic acid → 3-[(3,5-Di-tert-butyl-4-hydroxyphenyl)methylidene]-1,3-dihydro-2H-indol-2-one

Participants

Reaction Steps

A mixture of 3,5-di-tert-butyl-4-hydroxybenzaldehyde (5.28 g; 22.5 mmol), 2-oxindole (3.0 g; 22.5 mmol), and p-toluene sulfonic acid (0.25 g) in toluene (100 ml) is heated under reflux for 18 hours. The reaction mixture is cooled and filtered. The residue is washed with ether and dried @80° C. under vacuum for 18 hours to give 3.4 g (43.2%) of a yellow solid, mp 224°-225° C. (lit. mp 227° C.*).

Provenance & Evidence