Cyclopropylacetylene was prepared in a two-step procedure by dichlorination of cyclopropyl methyl ketone with phosphorus pentachloride (PCl5) followed by double dehydrohalogenation with a strong base. This sequence presented significant scale-up problems with low overall yields (20-25%).
Similarly, cyclopropylacetylene has been prepared by base-induced dehydrohalogenation of bromovinylcyclopropane . Cyclopropylacetylene has also been prepared from the 1-trimethylsilyl derivative of cyclopropylacetylene, which was prepared by treatment of 5-chloro-1-trimethylsilyl-1-pentyne with lithium diisopropylamide at ?78°C followed by warming to room temperature.
The general procedure for synthesizing cyclopropylacetylene from (1,1-dichloroethyl)cyclopropane was as follows: 1) 80 g of sodium hydroxide was mixed with 300 mL of ethoxyethanol and stirred at -60 °C, followed by the slow addition of 100 g of chlorocyclopropylacetylene at the same temperature. After the reaction was completed (the reaction process was monitored by gas chromatography analysis), atmospheric pressure distillation was performed to collect the 55 °C-65 °C fraction to obtain crude cyclopropylacetylene; 2) The crude cyclopropylacetylene was purified by distillation with continuous stirring. Finally, 59 g of cyclopropylacetylene with a purity greater than 98% was obtained, with a yield of 89%.
[1] Patent: CN105985223, 2016, A. Location in patent: Paragraph 0049; 0050; 0051; 0052
[2] Journal of Organic Chemistry, 1976, vol. 41, # 7, p. 1237 - 1240
[3] Synthesis, 1972, p. 703
[4] Journal of the American Chemical Society, 1972, vol. 94, p. 1158 - 1163
[5] Synlett, 1999, # 12, p. 1948 - 1950
