ca01 only detailed ToC 1..24

1.1.2 Nickel–Allyl Complexes 37
trated on a rotary evaporator and was separated by column chromatography (silica gel,
EtOAc/hexane) to afford 18 as an oil; yield: 0.112 g (82%).
1.1.1.6 Method 6:
Hydrocyanation of Dienes
The hydrocyanation of butadienes is the basis of DuPont s process for the production of
adiponitrile [hexanedinitrile (19), Scheme 11]. [33,34] The first step of the process involves
hydrocyanation of buta-1,3-diene to produce an isomeric mixture of pentenenitriles. In a
second step, nickel-catalyzed double-bond isomerization occurs to produce pent-4-enenitrile
followed by alkene hydrocyanation to produce adiponitrile (19). The details of the alkene
hydrocyanation reaction are discussed in further detail in Section 1.1.4.5.
Scheme 11 Hydrocyanation of Buta-1,3-diene [33,34]
HCN, Ni(0)
1.1.2 Product Subclass 2:
Nickel–Allyl Complexes
CN
+
CN
Ni(0)
CN
HCN, Ni(0) CN
NC
Nickel complexes with ç 3 -allyl ligands are important intermediates in a variety of catalytic
processes. The most straightforward methods of preparation involving the addition of
allyl electrophiles to nucleophilic nickel complexes and the addition of allyl nucleophiles
to electrophilic nickel complexes unambiguously lead to ð-allyl complexes. Aside from
these general classes of reactions, many other important catalytic processes potentially
involve ð-allyl intermediates although their intermediacy has not, in most cases, been established.
A very large variety of synthetic procedures involving nickel–ð-allyl complexes
have been developed including the addition of hard and soft nucleophiles, addition of
S N2-active and S N2-inactive electrophiles, and migratory insertions of alkenes and alkynes.
Synthesis of Product Subclass 2
1.1.2.1 Method 1:
Oxidative Additionof Nickel(0) with Allylic Electrophiles
A variety of nickel(0) complexes, when treated with allylic electrophiles, afford ð-allyl
complexes (see also Houben–Weyl, Vol. E 18, pp 64 and 76). [6,8] In early studies, tetracarbonylnickel(0)
was widely employed. However, owing to its extreme toxicity, it is now rarely
used. Direct treatment of bis(ç 4 -cycloocta-1,5-diene)nickel(0) (2) with allyl halides such as
20 is now the method of choice for the stoichiometric preparation of nickel–ð-allyl complexes.
In the absence of strong donor ligands such as phosphines, halo-bridged dimers
(e.g., 21) are typically obtained (Scheme 12). [35] In the presence of phosphines, monomeric
species such as 22 may be obtained. [35] Other less-electrophilic allylic substrates such as
allylic ethers and allylic alcohols also serve as precursors to nickel–ð-allyl complexes in
catalytic procedures. However, these precursors are less widely used than allyl halides in
the stoichiometric preparation of the ð-allyl complexes.
19
for references see p 79