Nitriles from organometallic compounds

With a,j -acetylenic nitriles, acetylenic organomagnesium compounds produce only the ketones resulting from 1,2-addition [4], Recently, the 1,4-addition of RMgX (R = saturated, vinylic, or allylic groups) and other organometallics to the conjugated structure of a-ethylidene-(Z)-1//-indole-2-acetonitrile has been observed [38] ... 

For an overall review, see Pombeiro, A.J.L. (1992) Electrochemical Behaviour of Complexes Derived from the Activation of Alkynes, Isocyanides and Nitriles , in A.J.L. Pombeiro and J.A. McCleverty (eds.). Molecular Electrochemistry of Inorganic, Bioinorganic and Organometallic Compounds, NATO ASI Series, Kluwer Academic Publishers, Dordrecht... 

Recently, we have studied the addition of organometallic compounds to aluminum-imines and silylimines which are easily prepared from nitriles and aldehydes ly treatment with diisobutyl aluminum hydride (DIBAH) and lithium hexamethyl disilyl... 

In spite of the fact that the above mechanism for formation of organometallic compounds during electrolysis of nitriles appears most probable to us, it is impossible not to mention another possible explanationfor this reaction. In electrochemical reduction of acrylonitrile organometallic compounds have been obtained from tin, sulfur, selenium, and tellurium, which are themselves reduced electrochemically. 

The experimental conditions for the syntheses starting from acid chlorides of hydroxamic acids and from nitrile oxides are somewhat different. In the former case the other component of the reaction is organometallic, usually an organomagnesium derivative of an acetylene or, less frequently, a sodium enolate of a /8-diketone. Nitrile oxides condense directly with unsaturated compounds. 

Not only alkenes and arenes but also other types of electron-rich compound can be oxidized by oxygen. Most organometallic reagents react with air, whereby either alkanes are formed by dimerization of the metal-bound alkyl groups (cuprates often react this way [80]) or peroxides or alcohols are formed [81, 82]. The alcohols result from disproportionation or reduction of the peroxides. Similarly, enolates, metalated nitriles, phenolates, enamines, and related compounds with nucleophilic carbon can react with oxygen by intermediate formation of carbon-centered radicals to yield dimers (Section 5.4.6 [83, 84]), peroxides, or alcohols. The oxidation of many organic compounds by air will, therefore, often proceed faster in the presence of bases (Scheme 3.21). 

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