Meerwein-Koelsch reaction

S) Attack on a polarized double bond in the Markovnikov sense is taken as evidence for a heterolytic reaction. If an addition follows the direction normally taken in the Meerwein-Koelsch reaction, a nonpolar reaction is indicated. Thus, for example, when benzenediazonium fluoborate is decomposed in ethyl crotonate, the product, after hydrolysis, is methylatropic acid. 

The reviews by Rondestvedt (1960, 1976) are outdated so far as the mechanism of the Meerwein reaction is concerned. This statement is substantiated by Rondestvedt s own comment in his 1976 review (p. 226) in which he states that the generally accepted mechanism involves the aryl radical. .., though the manner of its formation and its subsequent reaction are still controversial . Meerwein et al., in their original paper (1939), expressed the opinion that the reaction is ionic in nature. A radical mechanism was first proposed by Koelsch in 1943 (see also Koelsch and Bockelheide, 1944). He received immediate support from Bergmann et al. (1944) and Bergmann and Weizmann (1944), in spite of the fact that Koelsch s claim was based on rather uncertain and vague arguments. 

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See also in sourсe #XX -- [ ]

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