Metallation Reactions with Magnesium Amides

The chemistry of magnesium bis-amides has been reviewed.21 Magnesium bis-amides have been used for the region- and stereoselective formation of enolates.2 a Enantioselective enolization with chiral magnesium amides has been applied in asymmetric synthesis.23 233 

---

C. Metalation Reactions with Magnesium Amide Bases. 537... 

Scheme 3.8 Metallation reactions of bis(benzene)chromium and bis(toluene)chromium with alkali metal alkyls and magnesium amides ...

The first alkaline earth metal inverse crowns were discovered in the late 1990s via the fortuitous reaction of traces of O2 with a mixture of an alkali metal and a magnesium amide to afford complexes of e formulae (see Scheme 3.9) M2Mg2 N(SiMe3)2 4(O2)x(O)... 

Alkynyl anions are more stable = 22) than the more saturated alkyl or alkenyl anions (p/Tj = 40-45). They may be obtained directly from terminal acetylenes by treatment with strong base, e.g. sodium amide (pA, of NH 35). Frequently magnesium acetylides are made in proton-metal exchange reactions with more reactive Grignard reagents. Copper and mercury acetylides are formed directly from the corresponding metal acetates and acetylenes under neutral conditions (G.E. Coates, 1977 R.P. Houghton, 1979). 

Trialkylsilylamines and hexaalkyldisilazanes are obtained by the treatment of the corresponding amines or metal amides with trialkylchlorosilanes (eq (61)) [56]. The reactions of trialkylchlorosilanes with magnesium or lead thiolates afford trialkylsilyl sulfides (eq (62)) [57]. 

A further application of the metal-template effect in the ortho-regioselective acylation of phenols is represented by the direct synthesis of salicyloyl chloride and derivatives by the reaction of bromomagnesium phenolates 4 with phosgene. The reaction affords the unstable salicyloyl chloride-magnesium complexes 5 by a pathway similar to the mechanism depicted in Scheme 5.2. These intermediates can be in situ converted into the corresponding acids 6 (Scheme 5.3), esters, amides, or ketones by reaction with suitable reagents. 

---