Diphenylacetylene, from decomposition

If the crude title product (from interaction of 3-chloro-3-phenyldiaziridine and diphenylacetylene) is not purified immediately after preparation, violent decomposition occurs. 

The only trisilacyclopentene reported to date (99) results from the base-catalyzed decomposition of 1,2-dimethoxytetramethyldisilane and diphenylacetylene. It is fairly stable to air but reacts with moisture to give the oxatrisilacyclohexene (100 Scheme 178) (78CC1029). 

The double-addition products of type XVI are surprisingly stable. Complex 36 i, e.g., can be crystallized from CH2Cl2/MeOH in the presence of hydrochloric acid without substantial decomposition. The most striking property of 36i is the conversion into the cyclobutadiene complex 33 (R = Ph), which is more conveniently prepared from 28a and PhC2Ph at 150 °C. As already mentioned, the reaction proceeds by a stepwise mechanism through complexes XIV—XVI. This reaction offers a new, facile preparation of 33. The cyclo-dimerisation of alkynes other than diphenylacetylene could not been substantiated, however. 

Oxidation of acetylenes with N-bromosuccinimide in DMSO gives -dicarbonyl compounds in some cases. The yield using diphenylacetylene is practically quantitative. Oxidation with peracid has been studied using di-t-butylacetylene, and the products obtained compared with those obtained by decomposition of the related diazoketone (123). The primary products from the former were the a -unsaturated ketone (124) and the cyclopropyl-ketone (125). An almost identical ratio of products (124) and (125) was... 

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