Di-Grignard

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. 

Organobis(cupratesY, spiroannelation.16 1,4-Dilithiobutane, prepared from 1,4-dichlorobutane and lithium in ether at 0°, on reaction with copper thiophenoxide (2 equiv.) forms a biscuprate, formulated as 1 for convenience. This dimetallic reagent adds to 3-halo-5,5-dimethyl-2-cyclohexenones (2) to form the spiro-[4.5]decanone 3 in yields as high as 96%. Cuprates prepared from other Cu(I) sources are less efficient, as is the cuprate prepared from di-Grignard reagents... 

When acetylene is passed through a 0.5 to 1 molar solution of C2HjMgBr, kept just below 30 C (compare exp. 13) the solution initially remains clear, but there is a fair chance that the characteristic precipitate of BrMgOCMgBr appears (clearly different from the coarser suspension which is sometimes formed when solutions of HOCMgBr are cooled). If acetylene is introduced at 50 C into a-solution of C2HjMgBr, the suspension of the di-Grignard derivative is formed immediately. 

The trimethylsilylation of the di-Grignard derivative of acetylene has to be carried out at temperatures that are considerably higher than those necessary for the silylation of ethynyl mono-magnesium bromide. This decreased reactivity may be ascribed to the slight solubility of the intermediate. 

FIGURE 77. Molecular geometry of the 1,1-di-Grignard reagent 169 in the solid state... 

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 are known as derivatives of arsolane and stibolane. No derivatives of bismolane have been reported. They have been prepared by similar methods to those used for the preparation of arsetanes (equations 1, 2) and also by the reaction of the di-Grignard from 1,4-dibromobutane and a dichloroarsine or dichlorostibine (equation 3). 

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). 

A system with two cyclohexasilanyl substituents on one phenyl ring is obtained from the phenyl- 1,4-di-Grignard reagent and ClSigMen83,84 (equation 17). 

This synthesis can be extended to di-Grignard reagents (equation 1). 

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