Reactivity of [TismPriBenz]MgH and [TismPriBenz]MgMe Towards Esters: Alkoxide Elimination and C–C Bond Formation

The reactivity of Mg–H and Mg–Me bonds of [Tism Pr i Benz ]MgH and [Tism Pr i Benz ]MgMe towards esters reveals additional pathways to those that have been observed for aldehydes and ketones, namely insertion and enolate formation. For example, [Tism Pr i Benz ]MgH and [Tism Pr i Benz ]MgMe react with the formate ester HCO 2 Me to afford the methoxy derivative, [Tism Pr i Benz ]MgOMe, via a process that is proposed to involve β-methoxide elimination from a [Tism Pr i Benz ]MgOCH(X)OMe intermediate (X = H, Me). Likewise, [Tism Pr i Benz ]MgH reacts with the acetate ester, MeCO 2 Et, to afford the ethoxide complex, [Tism Pr i Benz ]MgOEt. In contrast, while the methyl complex [Tism Pr i Benz ]MgMe likewise reacts with MeCO 2 Et to form [Tism Pr i Benz ]MgOEt, the β-keto ester enolate derivative, [Tism Pr i Benz ]Mg(κ 2 -etac) [κ 2 -etac = MeC(O)CHC(O)OEt], is also obtained via a reaction that involves the formation of a C–C bond. The latter compound is additionally obtained by the reaction of [Tism Pr i Benz ]MgMe with ethyl acetoacetate, MeC(O)CH 2 C(O)OEt, presumably via a reaction with the enol tautomer, MeC(OH)CHC(O)OEt. [Tism Pr i Benz ]MgOMe and [Tism Pr i Benz ]Mg(κ 2 -etac) have been structurally characterized by X-ray diffraction.