Dichloromethane → 4-Isocyano-5,6-dihydro-1-benzothiophen-7(4H)-one

Participants

Reaction Steps

A sample of N-formyl-4,5,6,7-tetrahydro-7-oxobenzo[b]thiophen-4-amine (5.0 g) is dissolved methylene chloride (250 ml) under a nitrogen atmosphere and triethylamine (5.95 g) is added. Phosgene is then bubbled into the solution at 15° C and an exothermic reaction occurs. The temperature of the reaction mixture rises from 20° to 35° C and after 45 minutes, drops to 30° C. The flow of phosgene is terminated and nitrogen is then bubbled into the solution for about 20 minutes followed by ammonia gas. A brown precipitate is formed during the ammonia addition. The flow of ammonia gas is stopped when the reaction mixture becomes alkaline. The mixture is then flushed with nitrogen and is filtered to remove the precipitate. The filtrate is evaporated to dryness in vacuo, the residue is dissolved in ethanol (50 ml), the solution is filtered and evaporated to dryness in vacuo. The residue is scratched to afford a light brown solid, which is washed with water, dried and recrystallized from hexane-acetone to afford 2.1 g of the title isocyanide, m.p. 74° to 77° C.

Provenance & Evidence