Chemistry Reference
In-Depth Information
5
ASYMMETRIC CARBON - HETEROATOM
BOND- FORMING REACTIONS
YOSHIJI TAKEMOTO
Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku,
Kyoto 606 - 8501, Japan
HIDETO MIYABE
School of Pharmacy, Hyogo University of Health Sciences, Minatojima, Kobe 650-
8530, Japan
5.1. INTRODUCTION
Asymmetric carbon-heteroatom bond formations have been developed as fundamen-
tally important reactions [1a,b]. This chapter highlights the enantioselective reactions
catalyzed by transition metal complexes as well as the chiral Lewis acids, except for the
asymmetric reactions using organocatalyst or Brønsted acid. Particularly, the recent
results of the allylic substitution, the aza-Claisen rearrangement, the addition of hetero-
atom nucleophile to alkenes and allenes, the aziridination of alkenes, the
α
- amination/
α
-oxygenation of carbonyl compounds, and so on are summarized.
5.2. ALLYLIC SUBSTITUTION
An important variant for transition metal-catalyzed carbon-heteroatom bond formation
is allylic substitution [1]. The allylic substitutions of 1,3-symmetrical substrates have been
widely studied including enantioselective versions. Much effort has been directed toward
controlling the regioselectivity as well as enantioselectivity in allylic substitution of
unsymmetrical substrates
1
or
2
(Scheme 5.1). Palladium complexes are general and
versatile catalysts for allylic substitution. However, the palladium-catalyzed allylic
