Hydrocyanation of Olefins and Dienes

Hydrocyanation of olefins and dienes is an extremely important reaction [32] (about 75 % of the world s adiponitrile production is based on the hydrocyanation of 1,3-butediene). Not surprisingly, already one of the first Rhone Poluenc patents on the use of water soluble complexes of TPPTS described the Ni-catalyzed hydration of butadiene and 3-pentenenitrile (Scheme 9.10). The aqueous phase with the catalyst could be recycled, however the reaction was found not sufficiently selective. 

Allyl complexes have contributed significantly to the development of the organometallic chemistry of nickel and the applications of nickel complexes in organic synthesis, for example, nucleophilic attack on coordinated allyl ligands. In addition, allylnickel complexes have been identified as key intermediates in the oligomerization and cyclization of olefins and dienes. For example, the Ni(0)-catalyzed hydrocyanation of butadiene to adiponitrile, the main component of a major commercial process for the production of nylon, involves Ni (7r-allyl) intermediates. Moreover, the 77-rearrangements of allylnickel species have helped explain the facile isomerization of olefins in the presence of nickel complexes. The Ni-catalyzed homoallylation of carbonyl compounds with 1,3-dienes also involves Ni(7r-allyl) complexes this subject has been reviewed recently. New applications include the cleavage of G-G bonds in the deallylation of malonates, the preparation of cyclopentenones by carbonylative cycloaddi-... 

Palladium-catalyzed hydrocyanation of olefins has been reported [31]. However, the corresponding reactions with conjugated dienes have not been reported explicitly. The analogous nickel-catalyzed hydrocyanation of conjugated dienes has been described [32] and is the basis for the commercial adiponitrile process. In this case, it has been shown [33] that the overall addition of HCN to the 1,3-diene occurs with cis stereochemistry consistent with path B in Scheme 8-1. 

Many other addition reactions of olefins, dienes, and acetylenes are known, which are catalyzed by metal carbonyls including Ni(CO)4, Fe(CO)5, and Co2(CO)8 and by carbonyl derivatives such as hydrocarbonyls or phosphine-substituted carbonyls. Among these are the hydro-carboxylation, hydroesterification, and hydrocyanation of olefins the synthesis of hydroquiniones from acetylenes, carbon monoxide, and water ... 

Familiar combinations include Y = H, X = olefin, acetylene, or diene Y = alkyl, X = CO Y = OH or OR, X = CO or olefin. Such reactions constitute important routes for addition to unsaturated molecules, and thus play a widespread role in catalytic reaction processes such as hydrogenation, hydrosilylation, and hydrocyanation of olefins, car-bonylation, etc. ... 

The addition of hydrogen cyanide (HCN) to carbon-carbon double bonds activated by electron-withdrawing groups in the presence of a base as a catalyst (a variation of the Michael Reaction) has been known for a long time. Nitriles were also obtained by hydrocyanation of branched olefins, such as isobutylene and trimethylethylene, in vapor phase reactions in particular the reactions over alumina (3) and cobalt-on-alumina (4) were reported in the late 1940s and early 1950s. Addition of HCN to conjugated dienes in the presence of cuprous salts (vapor and liquid phase) was reported as early as 1947 (5). 

Besides the class of traditional phosphines ligands, the related class of phosphite ligands has been utilized as ancillary ligation in various industrially relevant processes such as the hydrocyanation see Hydrocyanation) of dienes or hydroformylation see Hydroformylation) or the copolymerization of CO and olefins.The thermochemistry of ligand substitution of a variety of phosphite ligands has... 

In the first stage Lewis acids are absent and further hydroeyanation of the monoolefm products 3-PN 40 and 2M3BN 41 does not readily oeeur. The monoeyanation of butadiene is similar to HCN addition to olefins. An individual feature of hydrocyanation of conjugated dienes is the intermediate appearance of TT-allylic complexes 43, which participate in the successive carbon-carbon coupling. Equations (12) and (13) demonstrate the reaction of butadiene with the hydrido-nickel complex 42 leading to formation of nitrile 40 (a) and explain the generation of byproducts, i.e., the branched nitrile 41 via an alternative pathway (b) [68-70]. 

Although they are often considered as poorer ligands than diphosphines, they lead also to very efficient and attractive enantioselective catalytic systems as exemplified here. As recent examples, diphosphinites 19 and 20 have been involved successfully in hydrogenation of olefins (mostly itaconate derivatives and enamides, up to > 99.9 % ee) ([84-89] and functionalized ketones (21) (up to 86 % ee) [90], hydrocyanation (19) [91], standard Pd-mediated allylic alkylation (20) [92] (up to 86% ee) [93], and Diels-Alder reaction between a,/l-enals and dienes (eq. (4) 99 % ee) [94]. 

In the metal catalyzed hydrocyanation area, the stage is set for major improvements in enantioselectivity for simple styrene derivatives. Asymmetric hydrocyanation of dienes and functionaUzed olefins is another exciting area ripe for further explorations. 

The kinetics and mechanism of nickel-catalysed olefin hydrocyanation have been reported , and the addition of DCN to cyclohexa-1,3-diene catalysed by [Ni (p 0Ph 3 )i ] is found to occur with cis-stereochemistry indicating cis-migration of coordinated cyanide in the intermediate ir-allyl complex. The reactions of various organic bromides RBr (R Ph, PhCH=CH, allyl, MeCH=CHCH2) with a mixture of bicycloheptene or bicycloheptadiene and alkynes R C=CH (R =Ph, hexyl, etc) catalysed by Ni(0) or Pd(0) complexes produce bicyclic compounds such as (55) . PhCH=CHBr reacts with bicyclo [2.2.1]hept-2-ene and R2NH (R2 = (CH2), (CH2)5,... 

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