Chlorosuccinimide → Succinimide

Participants

Reaction Steps

A solution of 10.73 g of 4-m-dithian-2-ylidene-6-fluoro-2,3-dihydro-4H-1-benzopyran in 107 ml of tetrahydrofuran was slowly added dropwise at room temperature to 26.7 g of freshly crystallized N-chlorosuccinimide dissolved in 210 ml of acetonitrile and 105 ml of ethanol. The mixture was stirred at room temperature for 3 hours, subsequently hydrolyzed by the addition of 100 ml of water, diluted with 1 l of water and extracted with three portions of ethyl acetate. The organic phases were washed twice with water and once with saturated sodium chloride solution, dried with sodium sulfate and concentrated to dryness in vacuo. Excess N-chlorosuccinimide and resulting succinimide were separated by filtration through a layer of silica gel 60 with hexane/ethyl acetate (19:1). The thus-obtained crude α-chloro-ethyl ester was dissolved in 85 ml of acetone, the solution was treated with 2.48 g of thiourea and the mixture was dried for 4 days. The initially clear solution liberated colorless crystals. These were separated, washed with acetone and recrystallized from ethanol/ethyl acetate, and there was obtained (±)-6-fluoro-2,3-dihydro-2'-iminospiro[4H-1-benzopyran-4,5'-thiazolidin]-4'-one hydrochloride of melting point 215°-217° C.

Provenance & Evidence