Grignard reagents as bases

W. Kosar, Grignard Reagents as Bases, in Handbook of Grignard Reagents (G. S. Silverman, P. E. Rakita, Eds.), Marcel Dekker Inc., New York, 1996, 441-454. 

Grignard reagents as bases alkyllithium reagents are not generally useful because of competing addition to the carbon-nitrogen double bond. Depending upon the experimental conditions e.g. solvent, temperature and base) and the nature of the N-substituent, deprotonation of the unsymmetrical ketimines (2 =... 

Reaction of a-sulphinyl carboxylic esters 421 with carbonyl compounds has usually been performed using a Grignard reagent as a base. No condensation products are obtained using t-butyllithium or sodium hydride367,496,497 (equation 251). The condensation products formed are convenient starting materials for the synthesis of a, p-unsaturated esters and /1-ketones497. 

The Bamford-Stevens reaction and the Shapiro reaction share a similar mechanistic pathway. The former uses a base such as Na, NaOMe, LiH, NaH, NaNHa, heat, etc., whereas the latter employs bases such as alkyllithiums and Grignard reagents. As a result, the Bamford-Stevens reaction furnishes more-substituted olefins as the thermodynamic products, while the Shapiro reaction generally affords less-substituted olefins as the kinetic products. 

The classic publication of a concerted mechanism appeared in the early 1950s [38] it picked up the idea of assistance by a second molecule of a magnesium species in reactions of Grignard reagents, as suggested earlier [41], based on erroneous observations (see p. 226). 

Use of a Grignard Reagent as a Base (Formation of Magnesium Unolates)... 

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