Cyclopropylacetylene is an hydrocarbon with the chemical formula .[1] Under normal conditions, the substance is a colorless liquid. Cyclopropylacetylene is a precursor pharmaceuticals and other organic compounds.
Several methods have been published on the synthesis of cyclopropylacetylene. The earliest preparation starts with the chlorination of cyclopropylmethylketone with phosphorus pentachloride.[2] Thereafter, the reaction product, 1-cyclopropyl-1,1-dichloroethane, is converted into cyclopropylacetylene via double dehydrochlorination. This occurs in presence of a strongly basic solution, such as potassium tert-butoxide in dimethyl sulfoxide:
However, the yield of this method is not substantial (20-25%).[3] A one-pot synthesis of cyclopropylacetylene has been reported in which 5-chloro-1-pentyne reacts with n-butyl lithium or n-hexyl lithium. Cyclohexane is used as a solvent. The reaction is a metalation followed by a cyclization. The reaction product is then cooled, and an aqueous solution of ammonium chloride is added slowly. There is a two-phase mixture: a heavy water phase and a lighter organic phase containing cyclopropylacetylene.[3]
Cyclopropylacetylene is used as reagent in organic reactions. It is, for example, a building block of the antiretroviral and psychotropic drug efavirenz. It can also be used in the azide-alkyne Huisgen cycloaddition.