Hydrochloric Acid → 7-Bromo-2-methyl-1H-indene

Participants

Reaction Steps

To a solution of 116 g (0.52 mol) of 4-bromo-6-chloro-2-methyl-1-indanone in 950 ml of THF-methanol (2:1, vol.) 38.3 g (1.02 mol) of NaBH4 were added in small portions for 2 hours at −5° C. (Caution: temperature must be lower than 0° C.). The mixture was stirred overnight at ambient temperature. The resulting mixture was poured over 1000 cm3 of ice and acidified with 10% HCl to pH=4. The organic layer was separated; the aqueous layer was extracted with 3×300 ml of methyl-tert-butyl ether. The combined organic fractions were dried over K2CO3 and evaporated to dryness. To the residue 1500 ml of toluene were added. This toluene solution was treated with a catalytic amount of pTolSO3H (ca. 2 g) for 2 hours at reflux. Then this mixture was cooled to room temperature and passed through a short Silica Gel 60 column (40-63 μm, d 60 mm, 140 mm). This column was additionally eluted with 250 ml of toluene. The chromatographed product was evaporated to dryness. Fractional distillation gave the title indene, b.p. 104-108° C./5 mm Hg. Yield 100 g (93%) of colorless solid.

Provenance & Evidence