Carbon Dioxide → 4,5-Dihydro-8-phenyl-5-thioxo-3H,6H-1,4,5a,8a-tetraazaacenaphthylen-3-one

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Reaction Steps

A mixture of 7.6 g of 4,5-dihydro-7-phenylpyrazolo[1,5-a]pyrimidine-3-carboxamide (prepared as described in Example 3) in 304 ml of dry tetrahydrofuran was stirred and cooled at -78° C. (dry-ice, acetone), under nitrogen and 2.17 g of sodium hydride (60% dispersion in mineral oil) was added. The mixture was stirred at -78° C. for 30 minutes, then 4.84 g of 1,1'-thiocarbonyldiimidazole was added in one portion. The temperature was kept at -78° C. for 2 hours, then was allowed to warm slowly to room temperature while stirring was continued for 48 hours. The reaction mixture was quenched with 500 ml of water and neutralized to pH 6-7 with 5% aqueous hydrochloric acid. A crystalline solid formed which was collected by filtration, triturated with ether, filtered and dried to give 3.2 g of the desired product as white crystals, m.p. 289°-291° C.

Provenance & Evidence