Benzophenones reactions with Grignard

Association between RMgX and Carbonyl Compounds Reactions of Benzophenone(s) with Grignard Reagents... 

Almost simultaneously, in 1963, another research group reported on the reaction kinetics of methylmagnesium species with benzophenone [40] (a preliminary communication of this work had appeared in 1961). These authors came to conclusions that differed considerably from the previous ones. Very explicitly they expressed as their opinion that ... the concept of the Grignard reaction with a ketone proceeding via a stable complex of the type described by Swain [see Ref. 38] is not supported by the published evidence [41] nor by the results of the present investigation. ... 

Maruyama and associates [53] proposed three mechanisms for reactions of Grignard reagents with benzophenone, in which differentiation is introduced for the C Mg bond strength in the respective reagent (see Scheme 17). 

Such differences in mechanisms can also be derived from the results of rate measurements (Table 1) of reactions of various Grignard reagents with benzophenone, carbon dioxide, and acetone, respectively. The reactivity series of Grignard reagents toward carbon dioxide [12] is comparable with the series for acetone [13], which led to the conclusion that both types of reactions follow the same mechanistic path a concerted mechanism. Steric requirements, therefore, are not the only parameter in the predictability of results of reactions of Grignard reagents and, in fact, are of little help when no other information on the reaction mechanism is available. 

Primary amines. Copper(I)-catalyzed Grignard reaction with the reagent gives (V-substituted imines. Acid hydrolysis releases the primary amines and the bis(trifluoromethyl)benzophenone. 

Figure 8.6 Grignard exchange reaction of C2F5I with MeMgCl followed by reaction with benzophenone in a microflow system...

In 1971 a study was made of the kinetics of the reactions of Grignard reagents with ben/ophenone using diethyl ether as the solvent 52. Included was an investigation of the products formed in the reaction. For r-bulylmagnesium chloride it was found that 50% of the product was the 1.4-dihydro-4-/-butylbenz.ophcnone. 44 4 was normal 1.2-addilion product and 69 was benzopinacol. 1.6-addilion to unstibslituied benzophenone had never been observed before, evidently because tile product easily oxidizes in air and decomposes thermally below IOO C. 

Kinetic isotope effects, which arc often a useful mechanistic tool, have been measured in several types of reactions of Grignard reagents including reactions with benzophenone. KIEs have been measured for the substitution of L1C and IJC... 

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