Crystal magnesium enolate

Magnesium alkoxide, simply prepared by dissolving magnesium in alcohol in the presence of a crystal of iodine, can be used to prepare magnesium enolates of bifunctional compounds. 

The first diastereoselective and enantioselective allylic alkylation of cyclohexanone (through the magnesium enolate 18a) with diphenylallyl acetate 19a was reported in 2000 by Braun and coworkers [16a]. (7J)-BINAP (23) served as the optimum chiral ligand, and the alkene 20 was obtained as an almost pure diastereomer with an enantiomeric excess of 99% ee. The relative configuration was proven by the crystal structure analysis the absolute configuration was assigned unambiguously by chemical correlation. A first diastereoselective and enantioselective Tsuji-Trost reaction of a lithium enolate derived from... 

If the organic layer is dried over magnesium sulfate and fractionally distilled at this point, both 2,4,4-trimethylcyclo-pentanone and 2-formyl-2,4,4-trimethylcyclopentanone, b.p. 49-50° (2 mm.), By 1.4495, may be isolated. The pot residue from this distillation contains a small amount of the enol form of 3,5,5-trimethyl-l,2-cyclohexanedione which crystallizes from petroleum ether as white needles, m.p. 92-93°. 

After almost half century of intensive, fundamental, and fruitful investigations of enolate structures, there is now clear evidence indicating that enolates of groups 1, 2, and 13 metals - lithium and boron being the most relevant ones - exist as the O-bound tautomers 1 the same holds in general for silicon, tin, titanium, and zirconium enolates [4]. Numerous crystal structure analyses and spectroscopic data confirmed type metalla tautomer 1 to be the rule for enolates of the alkali metals, magnesium, boron, and silicon [5]. 

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