Adiponitrile Synthesis via Hydrocyanation of Butadiene

These results could also be transferred to the synthesis of yS-lactones, depending on the oxygen location in the alkyne starting material. Several functional groups are tolerated, which broadens the synthetic applicability. If nitrogen-carrying substrates are employed, the two-step reaction results in the formation of the corresponding y-lactams 39b. 

The reduction of intermediately formed, isolable unsaturated nitriles opens up an easy route to regio- and stereo-chemically pure unsaturated aldehydes. The overall reaction is a regio- and stereo-selective hydroformylation of alkynes [61]. 

Newer investigations deal with the conversion of a-ketoalkynes to highly functionalized 3,5-substituted 5-hydroxy-3-pyrrolin-2-ones in a regioselective synthesis with KCN catalyzed by tetracyanonickelate(O) formed in situ from the system Ni(CN)2/CO/KCN in alkaline aqueous medium. This study is based on the catalytic hydrocyanation of alkynes in the presence of Ni(CN)4 introduced by Funabiki and co-workers [66]. 

The most outstanding example for the applieation of homogeneously catalyzed hydrocyanation is the DuPont adiponitrile process. About 75 % of the world s demand for adiponitrile is covered by hydrocyanation of butadiene in the presence of nickel(O) phosphite species. This process is discussed for the addition of HCN to dienes as an example, because in this case a well-founded set of data is available. Though it was Taylor and Swift who referred to hydrocyanation of butadiene for the first time [45], it was to Drinkard s credit that this principle was fully exploited for the development of the DuPont adiponitrile process [18]. The overall process is described as the addition of two equivalents of HCN to butadiene in the presence of a tetrakisphosphite-nickel(O) catalyst and a Lewis acid promoter. A phosphine-containing ligand system for the catalyst is not suitable, since addition of HCN to the tetrakisphosphine-nickel complex results in the formation of hydrogen and the non-aetive dicyano complex [67], In general the reaction can 

Equation (11) gives mechanistie proposals for the three different stages of the adiponitrile proeess. The initiating reaction stage affords via monohydrocyanation of butadiene two isomeric mononitriles, 3-PN 40 and 2M3BN 41 as the by-produet (cf. Table 3). A eopper-based catalyst has been reported that accomplishes the reaetion at this stage with 90% seleetivity to 3-PN [68], 

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