Trichlorocyclopropenyl cation

Since halogen attached to a cyclopropenyl ion can be displaced by a large number of nucleophiles, the trichlorocyclopropenyl cation 18 serves as a precursor, par excellence, for heterosubstituted cyclopropenyl cations, or cyclopropenes. A few of these are outlined in equation 23 without comment. The reader is referred to the review by Yoshida for a more detailed account of this area. 

Tetrachlorocyclopropene in the presence of Lewis acids or the trichlorocyclopropenyl cation are important starting materials in cyclopropenone syntheses In this method the cyclopropene or salt is reacted with benzene or derivatives of benzene bearing functional groups such as alkyl, alkoxy, hydroxy, or halogen to yield diaryl-substituted cations. Upon hydrolysis these cations yield the cyclopropenone. In some cases the monoaryl cation (32) can be obtained and converted to the aryl chlorocyclopropenone 33. Alternatively, the monoaryl cation can be reacted with a second aromatic species to give cyclopropenones with different aryl groups (equation 30). 

A, Favorskii method B, dihalocarbene method C, trichlorocyclopropenyl cation method. 

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See also in sourсe #XX -- [ ]

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