Diorganomagnesium compound

In fact, the use of dioxane to precipitate MgX2 from solutions of Grignard reagents is a standard method of preparation for solutions of diorganomagnesium compounds. Numerous methods have been used to estabUsh the nature of Grignard reagents in solution and this work has been reviewed (9). 

Chiral modification of diorganomagnesium compounds with the dilithium salt oi (S)-l,l -bi-naphthalene-2,2 -diol gave reagents with the empirical formula 30. Good to excellent enantiose-lectivities were observed in addition reactions of aliphatic and aromatic reagents to aromatic aldehydes30,31, however, the selectivities were not satisfactory with allylic, vinylic and acetylenic reagents. 

The organometallic reagent was prepared by adding the diorganomagnesium compound to the dilithium salt of (S)-l,1 -binaph-thalcnc-2.2 -diol, itself prepared by addition of 2 equivalents of BuLi to the chiral diol. b n.r. = not reported. 

B. Diorganomagnesium Compounds Containing Multi-hapto-bonded... 

F. Donor-Acceptor Complexes of Diorganomagnesium Compounds with... 

III. DIORGANOMAGNESIUM COMPOUNDS A. Donor-base-free DIorganomagnesium Compounds... 

FIGURE 29. Molecular geometries of diorganomagnesium compounds 48 and 49 in the solid state... 

C. Diorganomagnesium Compounds Containing Intramoiecuiariy Coordinating Substituents... 

It is rather surprising that only a few diorganomagnesium compounds have been reported in which intramolecular coordination of a heteroatom-containing substituent is present. The synthesis of (2-Me2NCH2C6H4)2Mg (67) was reported. It has been used in a study on the infiuence of the presence of potentially intramolecular coordinating substituents on Schlenk equilibria However, it has never been structurally characterized. 

Making use of the same procedure, the ether-functionalized diorganomagnesium compounds 76a-76f were prepared from 3-butenyl ethers and MgH2 (equation 11)"". It should be noted that the addition reaction of allyl ethers to MgHi failed because in that case ether cleavage by MgH2 becomes a competing reaction. Also, for these compounds intramolecular O-Mg coordination in solution was established by NMR spectroscopic studies. 

The second route (Scheme 1) is a redistribution reaction, in fact the Schlenk equilibrium. This route may be used in the reverse direction for the preparation of pure diorganomagnesium compounds from organomagnesium halides. Addition of a ligand, usually dioxane, that forms an insoluble complex with magnesium dihalide, shifts the Schlenk equilibrium completely to the left side and allows isolation of pure diorganomagnesium compounds from the remaining solution. ... 

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