Page 83 - Advanced Organic Chemistry Part B - Reactions & Synthesis

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SECTION 1.3
The Nitrogen Analogs of
Enols and Enolates:
cs
Enamines
0 10 1 and Imine Anions
C9
C8 N 6
O18 Li N1
C2
O201
C19
O20

Fig. 1.7. Crystal structure of lithium salt of SAMP hydrazone of 2-
acetylnaphthalene. Two molecules of THF are present. Reproduced
from Angew. Chem. Int. Ed. Engl., 27, 1522 (1988), by permission of
Wiley-VCH.

for the chloro-substituted group is observed. This reaction was used in the synthesis
of an ant alarm pheromone called S -manicone. Entry 3 is an alkylation of a methyl
group in an N,N-dimethylhydrazone. This reaction was used to synthesize analogs of
the antimalarial substance arteminsinin. Entries 4 to 6 take advantage of the SAMP
group to achieve enantioselective alkylations in the synthesis of natural products. Note
that in Entries 4 and 5 the hydrazone was cleaved by ozonolysis. The reaction in
Entry 6 was done in the course of synthesis of epothilone analogs. (See Section 13.2.5.
for several epothilone syntheses.) In this case, the hydrazone was first converted to
a nitrile by reaction with magnesium monoperoxyphthalate and then reduced to the
aldehyde using DiBAlH. 127

General References

D. E. Bergbreiter and M. Newcomb, in Asymmetric Synthesis, J. D. Morrison, ed., Academic Press,
New York, 1983, Chap. 9.
D. Caine, in Carbon-Carbon Bond Formation, Vol. 1, R. L. Augustine, ed., Marcel Dekker, New York,
1979, Chap. 2.
A. G. Cook, ed., Enamines: Synthesis, Structure and Reactions, 2d Edition, Marcel Dekker, New York,
1988
C. H. Heathcock, Modern Synthetic Methods, 6, 1 (1992).
V. Snieckus, ed., Advances in Carbanion Chemistry, Vol. 1, JAI Press, Greenwich, CT, 1992.
J. C. Stowell, Carbanions in Organic Synthesis, Wiley-Interscience, New York, 1979.

127
D. Enders, D. Backhaus, and J. Runsink, Tetrahedron, 52, 1503 (1996).