Cyclopropylacetylene

Cyclopropylacetylene is an hydrocarbon with the chemical formula C
5H
6.[2] Under normal conditions, the substance is a colorless liquid. Cyclopropylacetylene is a precursor pharmaceuticals and other organic compounds.

Cyclopropylacetylene
Names
Other names
Ethynylcyclopropane
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.102.389
Properties
C5H6
Molar mass 66.103 g·mol−1
Appearance colorless liquid
Density 0.781 g/cm3 at 25°C[1]
Boiling point 51–53 °C (124–127 °F; 324–326 K)
Hazards
GHS pictograms
H225, H315, H319, H412
P210, P273, P280, P305+351+338
Flash point −17 °C (1 °F; 256 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Synthesis

Several methods have been published on the synthesis of cyclopropylacetylene. The earliest preparation starts with the chlorination of cyclopropylmethylketone with phosphorus pentachloride.[3] 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:

Synthesis scheme 1

However, the yield of this method is not substantial (20-25%).[4] 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.[4]

Synthesis scheme 2

Applications

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.

References
  1. https://www.sigmaaldrich.com/catalog/product/aldrich/663018
  2. "CYCLOPROPYL ACETYLENE". chemicalland21.com. Retrieved 31 May 2017.
  3. Hudson, C.E.; Bauld, N.L. (1972). "Quantitative analysis of cyclopropyl β hyperfine splittings". J. Am. Chem. Soc. 94 (4): 1158. doi:10.1021/ja00759a021.
  4. Corley, Edward G.; Thompson, Andrew S.; Huntington, Martha. "CYCLOPROPYLACETYLENE". orgsyn.org. p. 231. doi:10.15227/orgsyn.077.0231. Retrieved 31 May 2017.
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