Cyclopropenones cyclopropenium salts

Following sections of this chapter discuss in turn cyclopropenium salts, cyclopropenones and other cyclopropene derivatives such as methylenecyclopropenes, also called triafulvenes. 

Cyclopropenones can be isolated from the organic phase either by extraction or by precipitation with strong acid42,43) in the form of stable, often well-defined proto-nation products, the hydroxy cyclopropenium salts 179 ... 

In accord with the relatively high basicity of cyclopropenone (pXb = - 5.2 0.3) and its derivatives (substituents at C(l) and C(2) increase the basicity alkyl more so than phenyl), these compounds are protonated in strong acids to give the corresponding hydroxy-cyclopropenium salts e.g. 321 (R = The salts generated in this manner can... 

Disubstituted cyclopropenones have been converted into trisub-stituted cyclopropenium salt s by treating them with either Orignard reagents [26,27], or a lithium alkyl [28],... 

Cyclopropenium salts, benzo, 162 Cyclopropenone, 164 preparation, 164 reactions, 167... 

Acetic anhydride (s. a. under H2O2) Cyclopropenium salts from cyclopropenones... 

A diaryl cyclopropenone (171) catalyses nucleophilic substitution of alcohols, for example, chlorination. Employing an activator such as oxalyl chloride [(COCl)2], a cyclopropenium salt (172) is generated and adds to the alcohol (to give 173), with the nucleophile then generating the product (with inversion of configuration), and regenerating the original cyclopropenone (171). The method shows considerable promise for dehydrations. ... 

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