Phosphorus sulfide (P2S5) → 2-Methyl-5,10-dihydro-4H-thieno[2,3-b][1,5]benzodiazepine-4-thione

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Reaction Steps

Combine 2-methyl-4,9-dihydro-3-thia-4,9-diazabenzo[f]azulene-10-one (21 g, 0.09 mol) and phosphorus pentasulfide (53 g, 0.12 mol) in pyridine (350 mL) and stir at room temperature overnight, heat at reflux for 5 h. Cool to room temperature to allow precipitate to settle, collect solid by filtration, wash cake with cold ethanol/water and air-dry for a few minutes to obtain 29 g of crude material. Take up solid in a small amount of pyridine, add a like volume of ethanol/water, sonicate for a few minutes and collect again by filtration. Air-dry cake, then place in the vacuum oven at 40° C. for 48 h to obtain 15.9 g of the title compound as an orange solid, which was used directly on the next step without further purification: melting point: 259.0-259.5° C.; Mass spectrum (APCI): m/z=247.0 (M+1).

Provenance & Evidence