Diethyl malonate magnesium derivative

The malonic acid derivative (1573) was prepared from diethyl 1-piperi-dinylmethylenemalonate with propen-1-yl magnesium bromide at 0°C (61BSF2423). 

The first is the acylation of the magnesium derivative of diethyl malonate. The magnesium atom prevents 0-acylation with acid chlorides, and decarboxylation (p. 678) removes the redundant ester group. 

The preparation of diethyl benzoylmalonate (entry 12) represents the use of an acid anhydride, a function in which it is much more reactive than an ester, as the acylating agent. The reaction must be carried out in nonnucleophilic solvents to prevent solvolysis of the anhydride from competing with the desired reaction. Other limitations on the use of highly reactive acylating agents, such as acid anhydrides and acid chlorides, in reactions with enolates derive from the fact that O-acylation may be the dominant reaction. The magnesium salt of diethyl malonate (entries 12 and... 

---