Preparation of 1,2-diMagnesiummethylbenzene

The  1,2-dimagnesiummethylbenzene showing below is a useful reagent for metal ligand preparation.
This di-grignard reagent  can be made in high yield from corresponding dichloride compound.

1,2-Dibromomethylbenzene can't be used because it can cause problem.

steps:
1. activate Mg using 1,2-dibromoethane.
2. in diluted solution, slowly add dichloride into Mg in THF. control temperature at rt.
3. allow 8 hr stirring at rt.

yield is over 95% in reports.

activation of Magnesium for grignard reaction

Grignard: Initiating the reaction is the tricky part, people have used 1,2-dibromomethane, iodine, TMSCl - but for me the best working initiation technique is to place few equivalents of Mg turnings into an oven-dried flask with a large egg-shaped stirbar, flush it thoroughly with dry argon, add few drops of Br2 and dry-stir the Mg turnings in the Br2 vapors overnight. Then add freshly distilled ether solvent via canula (the bromine color disappears) and then carefully your substrate. I got some Grignards like BrMg(CH2)3MgBr by this technique that are hard to make by other methods (unless you want to mess with Rieke Mg). The Mg turnings are fairly fragile and crushing them in oxygen-free and nitrogen-free environment uncovers a highly-reactive newly-formed surface which is further protected by MgBr2 formation. MgBr2 is soluble in ether. Please note that one has to use Ar because N2 reacts with fresh Mg surfaces, to produce dark Mg nitride.


http://chemknowhow.com/forum/viewtopic.php?t=448

Prepartion of magnesium bromide diethyl etherate solution

Once I was going to make a MgBr2-OEt2 1M solution in Ether.
When the ether was added into MgBr2-OEt2 powder, two layers of liquid was resulted.

Turned out the button layer contains MgBr2 at 39%wt. the top layer contains 3%wt.
addition of some benzene can increase the solubility and make a clear solution.

reference:
digital.library.okstate.edu/OAS/oas_pdf/v32/p79_82.pdf

note:
In a preparation, 1.5 M clear solution was made using 27 ml of Et2O and 4 mL of benzene at 25 C.

Synthesis of Silyl Enol Ethers by Mg/TMSCl

Tetrahedron Letters 40 (1999) 1349-1352

Synthetic utility and importance of silyl enol ethers have been well established [1-2]. The
numerous methods for their preparation have been reported [3-14] although some difficulties
have been encountered in the actual preparation, especially in the large-scale production,
owing to requirement of troublesome procedure, low temperature such as -78"C, special
equipment, carcinogenic solvent and/or expensive reagents.

In this study, we wish to present novel Mg-promoted coupling of aliphatic carbonyl
compounds with trimethylsilyl chloride (TMSCI) at room temperature to give the
corresponding silyl enol ethers in excellent to good yields. This
reaction may provide a highly convenient method for the stereoselective preparation of (Z)-isomers.

ref.
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[4] Pawkinko S., Organo Silicon Chemistry, Walter de Gruyter, Berlin, 1986.
[5] Weber W.P., Silicon Reagents for Organic Synthesis, Spring-Verlag, Berlin, 1983.
]6] Negishi E., Organometallics in Organic Synthesis, John Wiley & Sons, New York, Vol.l, Chap. 6, 1980.
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[ I 1
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[12] Dedier J., Gerval P., and Frainnet E., J. Organomet. Chem., lS$, 183 (1980).
[13] House ]t.O., Czuba L.J., Gall M.,and Olmstead H.D., J. Org. Chem., 34, 2324 (1969).
[14] Cazeau P., Duboudin F., Moulines F., Babot O., Dunogues J., Tetrahedron., 43, 2075 (1987).
[15] Ishino Y., Maekawa It., Takeuchi H., Sukata K., and Nishiguchi I., Chem. Lett., 1995, 829.