Metals reactions with Grignard

Whereas sulfolane is relatively stable to about 220°C, above that temperature it starts to break down, presumably to sulfur dioxide and a polymeric material. Sulfolane, also stable in the presence of various chemical substances as shown in Table 2 (2), is relatively inert except toward sulfur and aluminum chloride. Despite this relative chemical inertness, sulfolane does undergo certain reactions, for example, halogenations, ting cleavage by alkah metals, ring additions catalyzed by alkah metals, reaction with Grignard reagents, and formation of weak chemical complexes. 

A problem inherent in metallation reactions with Grignard reagents is the poor chemos-electivity of the reactions. The most common side-reactions are the competing nucleophile addition and the reduction of the carbonyl compounds. An interesting alternative would be to use the high electrophilicity of the Mg + cation and its tendency to form a multicoordinate complex. The preformation of a Mg(II) complex with a carbonyl compound or a carboxylic acid derivative enhances the acidity of the substrate to the point where a relatively mild base can be used. 

The work on vinyl sulphones and their reactions with Grignard reagents, in the presence of transition metal catalysts, all emanates from Julia s laboratory191-195, with the exception of a note196 that presents evidence for SET processes in the alkylation of vinyl sulphones by organometallic reagents. 

This type of reaction involves both oxidation and addition of groups, so it is known as an oxad reaction. Alkyl derivatives of PC13 can be prepared by the reactions with Grignard reagents and metal alkyls illustrated in the following equations ... 

TABLE 2. Structurally characterized organomagnesium amides synthesized from the reaction of metal amides with Grignard reagents... 

Dithioacetals (see also dithianes and dithiolanes) alkylation of 98 as acyl anion equivalents 75 carbanions of 87,97-102 cleavage of 14-18,98,102 desulfurization of 78 metal-catalysed coupling 127 reaction with Grignard reagents 127 reductive lithiation of 89 synthesis of 12-19,97-102 Dithioacids synthesis of 40... 

As mentioned in Section 4.2.2.6, dithioacetals can be used in coupling reactions with Grignard reagents in sequences leading to the formation of carbon-carbon single and double bonds. The metal-catalysed reactions depicted here exemplify their uses for olefination reactions, which opened the way to many useful synthetic applications [319],... 

Fundamental Reactions of Transition Metal Complexes Comparison of Transition Metal-catalysed Reactions with Grignard Reactions... 

The formation of disilane derivatives is not possible only with metals organometallic compounds also react with halosilanes. West et al.509 found formation of disilanes in the reaction with Grignard compounds ... 

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