Organomagnesium reagents reactions with carbonyl compounds

The reaction of Grignard reagents with carbonyl compounds has no direct biological counterpart, because organomagnesium compounds are too... 

The conjugate addition of organocopper reagents to polyalkenic carbonyl compounds presents an opportunity in which either 1,4-, 1,6- and sometimes 1,8-addition can occur. Much of the early woik in this area was conducted in the study of the reaction of a dienoate or dienone with an alkylcuprate or a catalytic copper/organomagnesium combination. The predominant mode of addition for the reaction of a dienoate and a copper-based organomagnesium reagent was found to be 1,6 not 1,4.72 If the opportunity of 1,8-addition was present, then this mode prevailed.73 However, a truly systematic study has not been carried out with the various reagents. 

The complexities of their constitution in solution make studies of the mechanism of reactions of organomagnesium compounds extraordinarily difficult. Few reactions have stimulated such a wealth of elegantly planned and meticulously executed experiments as those of Grignard reagents with carbonyl compounds (see Section 6.1). Fortunately an admittedly grossly oversimplified rationale for the reactivity of organomagnesium compounds, and in particular for the influence of solvation, is adequate for most applications in organic synthesis. In a monomeric, unsolvated species (2),... 

Apart from these SET reactions, solvent effects in reactions of organomagnesium reagents with carbonyl compounds have been studied rather extensively. The reaction of ethylmagnesium bromide with benzophenone (Scheme 15) in diethyl ether yields 94% of the expected addition reaction product, 1,1-diphenyl-1-propanol, and 6% benzhydrol, resulting from a reduction reaction of the Grignard reagent [36]. In tetrahydrofuran this reaction yields 21 and 77%. respectively, of both products. 

The reduction of carbonyl compounds by reaction with hydride reagents (H -) and the Grignard addition by reaction with organomagnesium halides (R - +MgBr) are examples of nucleophilic carbonyl addition reactions. What analogous product do you think might result from reaction of cyanide ion with a ketone ... 

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