Carbon Monoxide as a Raw Material in Organic Synthesis

Organo transition metal σ-complexes undergo carbon monoxide insertion reactions under comparatively mild conditions. Carbonylation of phenyl derivatives of transition metals known to form metal carbonyls yields benzophenone. Pentacyano benzylcobaltate is inactive towards carbon monoxide but the coordinatively unsaturated tricyano benzylnickelate absorbs carbon monoxide at 0°C in aqueous solution to give dibenzyl ketone. A variety of organolithium compounds are found to react with carbon monoxide at -70°C to give symmetrical ketones.Amines undergo carbonylation reaction with carbon monoxide in the presence of metal carbonyls or carbonyl selenide to produce 1, 3-dialkyl ureas. Especially, carbonyl selenide is an excellent carbonylating agent to amines and may be used as a catalyst.The halides which contain unsaturated bond at the β, γ-position of the halides are found to be reactive towards metal carbonyls (iron or nickel) and to give unstable σ-complexes as intermediates, whose decomposition yields dimers, ketones or β-epoxy ketones. The reaction of benzyl halides or iodobenzene with metal carbonyls (nickel or iron) in the presence of certain olefins gives benzylation or phenylation products of the olefins.Organolithium compounds add to metal carbonyls reductively to form lithium acyl- or aroylmetal carbonylates, which are found to be useful reagents, for organic synthesis. The synthesis of aldehydes, 1, 4-diketones and unsymmetrical ketones have been achieved by using these acyl- or aroylmetal carbonylate reagents.