The 1,3-cycloaddition reaction of 2-diazopropane with diphenyldiacetylene leads to the mixture of 3,3-dimethyl-5-phenyl-4-phenylethynyl-3H-pyrazole, 3,3-dimethyl-4-phenyl-5-phenylethynyl-3H-pyrazole, and 3,3,3',3'-tetramethyl-4',5-diphenyl-4,5'-bi-3H-pyrazolyl. Photolysis of both 3H-pyrazoles gives the title phenylethynylcyclopropene.
Kuznetsov; Kuchuk; Tunik, Russian Journal of Organic Chemistry, 1998, vol. 34, # 2, p. 245 - 249