Di-Grignard compounds

Fig. 5.44. Electrophilic functionalization of an aromatic di-Grignard compound synthesis offi-BINAP. (Enantiomerically pure BINAP is one of the most important ligands in asymmetric catalysis, cf. Figures 17.76 and 17.77.)...

Fig. 5.37. Electrophilic functionalization of an aromatic di-Grignard compound synthesis of /M1INAR...

The best known compounds of this class are benzosilepines. The classical reaction is the cyclization of the di-Grignard compound of l,2-bis(j5-bromoethyl)benzene (388) by means of substituted dichlorosilanes (1/58/117/219) to afford 3-substituted 1,2,4,5-tetrahydro-3//-3-benzosilepines (389a-d) (equation 175)197. 389a and d can easily be brominated by means of NBS to yield the corresponding 1,5-dibromo compounds... 

The corresponding reactions of diiodoacetylene are very fast even at 0° and give 75-95% yields of alkyl and aryl iodides.436 As the di-Grignard compounds from acetylene are sparingly soluble in ether, the equilibrium... 

The alkine bromides (XI) were obtained according to Osbond and Wickens (26) by reacting the alldne bromides (VI) with the di-Grignard compound of propargylic alcohol in tetrahydrofuran catalyzed by cuprous chloride. In this way substances were prepared (Xla)-(XId) ... 

Hogenbiik M, Schat G, Akkerman OS, Bickelhaupt F, Smeets WJJ, Spek AL (1992) The first X-ray structure of a 1,1-di-Grignard compound bis(bromomagnesio)bis(tiimethylsilyl)meth-ane. J Am Chem Soc 114 7302-7303. doi 10.1021/ja00044a056... 

The stereochemistry of the 1,4-addition to A -octal-l-one and 1,1-di-methyl-A -octal-2-one has been investigated by House and Marshall, respectively. In summary, steric and stereoelectronic factors play a part in the mechanism of conjugate addition of Grignard compounds. With methylmagnesium iodide, the introduction of an axial methyl group into steroidal 5a-A -3-ketones (3) and 5 -A -3-ketones (6) is favored by stereo-electronic factors in the transition state. 

First examples of complexes of a,cj-digold alkylidenes have been prepared in moderate yields from the corresponding di-Grignard reagents with 2 equiv. of (Ph3P)AuBr as colorless, crystalline products. The structure of the dinuclear compound with the -(CH2)4- spacer has been determined (Equation (3)).19 Preparative efforts oriented at the synthesis of the analogous ethane, propane, and hexane derivatives were unsuccessful. 

Li, Na, or Grignard compounds of cyclopentadiene, indene, or fluorene add to di-substituted cyclopropenium cations forming cyclopentadienyl cyclopropenes, which can be transformed to calicenes by subsequent hydride abstraction and deprotonation, as shown by the following examples 9S91 and 9992 (cf. p. 13) ... 

For formation of 1,2-dilithio compounds and 1.2-di-Grignard reagents, but not by this method, see van Eikkema Hommes Bickelhaupt Klumpp Reel. Trav, Chim. Pays-Bas 1988, 107. 393. Angew. Chem. Ini. Ed. Engl. 1988, 27. 1083 [Angew. Chem. 100, 1100],... 

These compounds (92) are prepared by the reaction of the dibromoethyl material (91) with either the disodium salt (43JCS547) or the di-Grignard reagent (50JCS1917) derived from a monoalkyl- or monoaryl-arsine with best yields reported from the latter route (Scheme 19). 

In general, two procedures are most often reported for the preparation of platinacyclopentane compounds. The reaction of the di-Grignard reagent BrMg (CH2)4MgBr with dichloro(l,5-cyclooctadiene)platinum(II) is followed by the... 

The platinacycloheptane 112 was synthesised in 3% yield by the reaction of (COD)PtCl2 with a appropriate di-Grignard, and subsequent reaction with PPh3 displaced the COD ligand (Scheme 35). The products of thermal decomposition of 112 at 60 °C were found to be 1-hexene (83%) and 2-hexene (17%). Interestingly, compound 112 is reported to be less thermally stable than the five- and six-membered ring analogues.80... 

The halogen compound reacts with tetramethylene di-Grignard to yield 5,6,11 trisilaspiro-4,6-undecane as an oil. 

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