1,3-Dibromo-5,5-dimethylhydantoin → 5-Bromo-2,3-dihydro-7-azaindole

Participants

Reaction Steps

A solution of 7-azaindoline (22.7 g, 189 mmol), p-toluene sulphonic acid monohydrate (2.95 g, 15 mmol) and 1,3-dibromo-5,5-dimethylhydantoin (27.4 g, 96 mmol) in methylene chloride (1500 ml) was stirred at ambient temperature for 3 hours. The reaction solution was then decanted from a black polymeric material; washed with 0.2 M sodium thiosulphate (4×250 mls) followed by brine and dried over magnesium sulphate. The filtrate was evaporated under vacuum to give a black solid which was extracted with boiling ethyl acetate (2×800 mls and 2×500 mls). The combined extracts were heated at reflux for a few minutes with decolourising charcoal, filtered and evaporated under vacuum to give 5-bromo-7-azaindoline (16.6 g, 44%).

Provenance & Evidence