Phosphorus oxychloride → 6,7-Dihydrobenzo[b]thiophene-4-carbonitrile

Participants

Reaction Conditions

Reaction Steps

Boron trifluoride diethyl etherate (120 drops) was added dropwise under nitrogen at ambient temperature to a stirred mixture of 6,7-dihydrobenzo[b]thiophen-4(5H)-one (130.5 g) and trimethylsilyl cyanide (98 g), the mixture was stirred at ambient temperature for 2 hours and at 100° C. for 1 hour, then it was allowed to stand at ambient temperature for 18 hours. Pyridine (650 ml) followed by phosphorus oxychloride (125 ml) were added, the mixture was heated at 140° C. for 2 hours whilst volatile materials were removed by distillation, then it was cooled to ambient temperature and added to crushed ice (2000 ml). Ether (2000 ml) was added and the mixture was filtered through Celite. The filter pad was washed with ether (500 ml), the aqueous phase was separated, and further product was extracted from it using ether (500 ml). The ethereal solutions were combined, washed with water (500 ml), 5M hydrochloric acid (2250+500 ml), water (500 ml) and saturated aqueous sodium chloride solution (500 ml), then they were dried (MgSO4) and the solvents were removed in vacuo to give crude 6,7-dihydrobenzo[b]thiophene-4-carbonitrile (88.3 g) as an orange oil which was used without further purification.

Provenance & Evidence