Methanol → 6-Hydroxyindoline

Participants

Reaction Steps

To a stirred mixture of 5.8 g of the crude acid above, 65 ml of methanol was added dropwise 5 ml of trifluoromethanesulfonic acid. This mixture was stirred and heated under reflux for 12 hr when TLC (silica gel developed with HOAc/MeOH/CH2Cl2 1:5:45 or 10% triethylamine in ethanol) showed little starting material left. The reaction mixture was cooled, diluted with 75 ml of saturated sodium bicarbonate solution and cooled overnight in the refrigerator. The solid was collected to give 4.3 g of still damp black material. This solid was chromatographed on 100 ml of silica gel packed in 5% methanol/methylene chloride. Elution with 200 ml of 10% methanol/methylene chloride gave 2.7 g (theory from 6-hydroxy indoline 5: 5.46 g or 49% for the two steps) of impure product.

Provenance & Evidence