Water → 3,4-dihydrothieno[3,2-f][1,4]thiazepin-5(2H)-one

Participants

Reaction Steps

To 300 g of polyphosphoric acid warmed at 70° C. was added 19.5 g of 5,6-dihydro-4H-thieno[2,3-b]thiopyran-4-one 4-oxime portionwise with stirring for 20 minutes. The mixture was stirred at 80° C. for 2.5 hours, poured into chilled water and extracted with chloroform. The extract was washed with water, dried over magnesium sulfate and concentrated under reduced pressure. The resulting crude crystals were recrystallized from ethanol to give 10 g of 2,3-dihydrothieno[3,2-f]-1,4-thiazepin-5(4H)-one as white crystals, melting at 195°-196° C.

Provenance & Evidence