Phosgene → Methyl 2-[(oxomethylidene)sulfamoyl]cyclopent-1-ene-1-carboxylate

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Reaction Steps

In 75 ml of dry xylenes was placed 4.0 g of methyl 2-(aminosulfonyl)-1-cyclopentene-1-carboxylate (VIII), 6.5 ml of n-butyl isocyanate, and 0.05 g of DABCO. The mixture was heated to reflux (ca 138°) then contacted with an excess of phosgene which was condensed into the mixture from a dry-ice condenser until the reflux temperature dropped to 126°. Over several hours the temperaure increased to 135° and additional phosgene was condensed into the mixture, again, lowering the temperature to 129°. This process was repeated until no temperature increase could be observed, indicating complete consumption of the sulfonamide. The mixture was then cooled and the xylenes removed under reduced pressure to yield ca 5 g of an amber oil. An infrared spectrum (neat) exhibited a strong absorption at 2230 cm-1 indicating the title compound.

Provenance & Evidence