TRANSITION METAL -CATALYZED HOMOGENEOUS ASYMMETRIC HYDROGENATION - Catalytic Asymmetric Synthesis - page 421

Ir-P,N-ligand
H 2 ,I 2 ,rt,toluene

N R

N R
NHBz

N Bz
R=alkylgroups R=alkylgroups

50-90% ee (7.58)

In addition to the studies on the hydrogenation of indoles, quinolines, pyrole, and
pyridines, furans were also studied in asymmetric hydrogenation. Pfalz and others
reported a hydrogenation of furan derivatives using an Ir complex of pyridine-phosphi-
nite ligand. A range of 78-99% ee was achieved under 100 atm of hydrogen (Eq. 7.59)
[399]. Other attempts using Rh-ButiPhane or Ru catalysts only returned unsatisfactory
results [400] .

Ir catalyst
50-100 atm H 2 ,40 o C, CH 2 Cl 2

O

O

∗

R

R

78-99% ee

(7.59)

7.4. CONCLUSION

Chemists worldwide have witnessed the fast development of transition metal-catalyzed
homogeneous asymmetric hydrogenation during the past few decades. Hundreds of
catalytic systems with various structural and electronic properties have been prepared.
A large number of chiral building blocks and pharmaceutical products have been syn-
thesized through asymmetric hydrogenation. Many catalysts have also been employed
in industrial-scale processes. The highly effi cient and environmentally friendly natures
of homogeneous asymmetric hydrogenation will undoubtedly be further recognized in
both laboratory synthesis and industrial manufacturing. The development of asymmetric
hydrogenation will continue to be of great interest especially for some currently chal-
lenging substrates. The signifi cant impact of homogeneous asymmetric hydrogenation
on other areas of asymmetric catalysis will also be realized.

REFERENCES

1. For selected reviews on catalytic asymmetric hydrogenation, see: (a) de Vries , G. ; Elsevier , C. J.
(Eds.). Handbook of Homogeneous Hydrogenation . Weinheim : Wiley - VCH , 2007 . (b) Chaloner , P.
A. ; Esteruelas , M. A. ; Jo ó F. ; Oro , L. A. Homogeneous Hydrogenation . Dordrecht : Kluwer , 1994 .
(c) Brown , J. M. In Comprehensive Asymmetric Catalysis (Eds. Jacobsen , E. N. ; Pfaltz , A. ; Yama-
moto , H. ). Berlin : Springer , 1999 ; Vol. 1, Chapter 5.1, pp. 121 - 182 . (d) Noyori , R. In Asymmetric
Catalysis in Organic Synthesis (Ed. Noyori , R. ). New York : Wiley & Sons , 1994 ; Chapter 2, pp. 16 - 94 .
(e) Tang , W. ; Zhang , X. Chem. Rev. 2003 , 103 , 3029 .

2. (a) Ojima , I. (Ed.). Catalytic Asymmetric Synthesis . New York : VCH , 2000 . (b) Noyori , R. Asym-
metric Catalysis in Organic Synthesis . New York : Wiley , 1994 . (c) Jacobsen , E. N. ; Pfaltz , A. ; Yama-
moto , H. (Eds.). Comprehensive Asymmetric Catalysis . Heidelberg : Springer , 1999 ; Vol. 1 - 3 .

(d) Blaser , H. - U. ; Spindler , F. ; Studer , M. Appl. Catal. A Gen . 2001 , 221 , 119 .