_P.-Powell-auth.-Principles-of-Organometallic-Chemistry-Springer-Netherlands-1988

Five electron ligands
Nucleophilic reagents include R 2 Cd, NaCH(C0 2 Me) 2 , Ro-. R 2 NH, activated
aromatics such as 1, 3-dimethoxybenzene, allylSiMe 3 , BH; and CN-. Lithium
alkyls in dichloromethane at low temperatures give good results, but not in
diethyl ether. Tertiary amines and phosphines form quaternary salts.
The 2-methoxycyclohexadienyl complexes are particularly useful in synthesis.
The methoxy substituent directs nucleophiles to the remote end of the dienyl
system. This directive effect is strong enough to overcome the steric hindrance of a
methyl substituent at the 5-position, although a mixture of products is obtained
with the 5-ethyl complex.
OMe
(Me02C)2CH>c>
+ w' ~ Fe(CO)
...0 3
El
(only produci, R=H, Me)
(R=EI)
Spirocyclic compounds have been prepared by making use ofthe regioselectivity
of these reactions. Dienyl complexes were constructed which contained latent
nucleophiles in the side chain which were released on treatment with a mild base.
Similar reactions have also been used to introduce angular substituents into
bicyclic systems.
Fe(C0) 3
~OM o
~6~~3
~
CH(C02 Me)2
Pearson and his coworkers have used 1] 5 -dienyliron salts in approaches to the
synthesis of many natural products, including steroids, alkaloids and
sesquiterpenes.
9.6 References
Caulton, K.G. (1981) Coordination chemistry ofthe Mn and Re fragments, (C,H,)M(C0) 2 •
Coord. Chem. Revs., 38, 1.
Ernst, R.D. (1985) Open-chain metallocenes. Ace. Chem. Res., 18, 56.
Palier, J.W. (1978) Fluxional organometallics. Adv. Organomet. Chem., 16, 211.
Haaland, A. (1979) 3d-Metallocenes. Ace. Chem. Res., 12, 415.
Hunt, C.B. ( 19 77) Metallocenes. Educ. Chem., 14, 11 O.
Jonas, K. (1985) Reactive organometallic compounds obtained from metallocenes. Angew.
Chem. (Int. Edn), 24, 295.
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