Hypervalent Iodine-Catalyzed Oxidative Reactions:
The Curious Case of Organocatalysis
Pihko Group Seminar
Sep 5, 2011
Billy Yip
Outline
1.
Definition of Hypervalency
i.
Background
2.
Stoichiometic Uses1
i.
Overviews of Hypervalent Iodine Compounds
3. Examples involving Catalytic turnover2
i.
Alcohol Oxidation
ii.
Oxidative Dearomatization
iii. α-Oxidation of Ketone
iv. Other reactivities
4.
Conclusion
Key Reviews:
1 a) Stang and Zhdankin Chem. Rev. 1996, 96, 1123. b) Moriarty et al. J. Org. Chem. 2005, 70, 2893. c) Zhdankin
and Stang Chem. Rev. 2008, 108, 5299. d) Olofsson et al. Angew. Chem. Int. Ed. 2009, 48, 9052. e) Zhdankin et al.
J. Org. Chem. 2011, 76, 1185.
2 a) Ishihara et al. Chem. Commun. 2009, 2086. b) Kita et al. Chem. Commun. 2009, 2073. c) Ochiai et al. Eur. J.
Org. Chem. 2008, 4229.
Hypervalent Iodine Family
Recent Review on IBX:
A. Duschek, S. F. Kirsch Angew. Chem. Int. Ed. 2011, 50, 1524.
Stoichiometric Use of Hypervalent Iodine
Alcohol Oxidation
Unraveling Twisting in IBX
Oxidative Dearomatization
α-Oxidation of Ketone
Other Reactivities
Concluding remarks and Perspectives
Advantages of hypervalent iodine catalysis:
1. Readily available and cost-effective
2. Green oxidation (H2O2 , Oxone as terminal oxidant)
3. ”Metal-like” reactivities under ”metal-free” conditions
i.
ii.
Variable oxidation states (I/III) and (III/V)
Activation to hetero- and carbo-nucleophiles, alkynes, arenes
4. Versatile catalyst designs (iodoarene, iodide salts, solid-support…etc)
5. Versatile reactivities (SET, ionic pathways)
6. Environmentally-friendly co-product (low valent iodine, oxidant waste)
Challenges to be addressed:
1. Greener oxidant (other than mCPBA)
2. Better enantio-control
3. Better S/C ratio (higher turnover)
”… A motto in our research group became when
in doubt, think hypervalent iodine.” - Robert M. Moriarty
J. Org. Chem. (Perspective) 2005, 70, 2893-2903.