1. Asymmetric Photochemistry Liu-Zhu Gong Group Meeting September 12, 2009 Wei-Jun Liu 1.Fundemental Reaction 2.Solid-Phase 3.Solution-Phase Covalently-bound chiral auxilliaried Chiral complexing agents Chiral sensitizer Review: Rau, H. Chem. Review. 1983, 83, 535-547. Inoue, Y. Chem. Review. 1992, 92, 741-770. Konig, B. Chem. Review. 2006, 106, 5413-5430. Fagnoni, M. Chem. Review. 2007, 107, 2725-2756. Hoffmann, N. Chem. Review. 2008, 108, 1052-1103.

2. 1.Fundmental Reactions 1.1 [2+2] photocycloaddition Synlett 2002, 1305 J. Am. Chem. Soc. 2009, 131, ASAP.

3. Paternò-Büchi Reaction (between a ketone and alkene) J. Org. Chem. 2003, 68, 9899. J. Org. Chem. 2004, 69, 33. Ang. Chem., Int. Ed. 2003, 42, 1642

4. 1.2 Photochemical Rearrangments (di-ПЛ Synthesis 2001, 1175

5. The Herteroatom Variant Photochemical Rearrangments Ang. Chem., Int. Ed. 2002, 41, 4090

6. 1.3 Norrish-Yang Reaction Synthesis 2001, 1253

7. 1.4 Intermolecular Addition onto Double or Triple C-C Bonds J. Org. Chem. 2001, 66, 7320.

8. 1.5 Photo-oxygenation

9. Why Study Asymmetric Photochemistry? Prebiotic photochemistry ---- enantiomeric excess of biomolecules may have been generated by circularly polarized light (CPL) Environmentally benign processes ---- light is ubiquitous, generates no waste. Different mode of reactivity ---- access to novel, strained compounds which are thermally inaccessible or diffcult to synthesize and low reaction temperature Short excited lifetime low activation energy for reactions in excited states Why few Examples in Enantioselective Photochemical Transformations A few energy difference of a few kilocalories per mole is sufficient to give >99% stereodifferentiation. Inoue, Y. Chem. Review. 1992, 92, 741-770.

10. 2. Enantioselective Solid-Phase Photochemistry 2.1 Host-Gest Cocrystals Toda, Chem. Comm. 1995, 621

11. 100% ee Toda, Tanaka ACIE, 1999, 38, 3523 91-99.5% ee Tanaka OL, 2002, 4, 3255

12. 2.2 Ionic Chiral Auxiliary Scheffer ACR, 1996, 29, 203

13. 2.3 Chiral Modified Supercages of Zeolites Ramamurthy ACR, 2003, 36, 509

14. 3. Enantioselective Solution-Phase Photochemistry 3.1 Covalently-bound chiral auxillaries Meyer, JACS, 1986, 108, 306

15. Carreira, JACS, 1994, 116, 6622 JACS, 1997, 119, 2597

16. 3.2 Chiral Complexing Agents (Templated Photochemsitry) 3.2.1 Noncovalent Asseemblies EJOC, 2002, 2298

17. JOC, 1995, 60, 7984 Glycol-Metal Cation

18. Diaminotriazine-barbiturate ( 二氨基三唑－巴比妥酸盐）

19. CR, 2006, 106, 5413-5430

20. 3.2.2 Complementary DNA Strands as Templates CR, 2006, 106, 5413-5430

21. 3.2.3 Templates with a Covalently Bound Chromophore and Recognition Site The reaction did not proceed in the absence of the template

22. As an artificial functional model of a photolyase CR, 2006, 106, 5413-5430

23. 3.2.4 Photochemical reaction in a molecular flask The molecular flask is significantly larger than the guest and can therefore protect Substrates from the surrounding environment and thus controls the course of a Photochemical reaction. The syn isomers were the major. The syn isomers changed to the minor. Favorite temperate scaffolds Good availability Various sizes Inherent chirality CR, 2006, 106, 5413-5430 Cyclodextrin

24. Self-Assembled Molecular Cage

25. 3.2.5 Templates Containing a Shield Mori and Nakamura, TL, 1996, 37, 8523-8526

26. Bach, T. JACS, 1999, 121, 10650-10651

27. Bach, T. ACIE, 2000, 39, 2302-2304

28. Bach, T. JACS, 2000, 122, 11525-11526

29. Bach, T. ACIE, 2003, 42, 3693-3696

30. Bach, T. OL, 2001, 3, 601-603 Bach, T. CC, 2001, 607 Bach, T. CEJ, 2002, 8, 2464

31. Catalytic Enantioselective Photochemical Reaction Krische, J. JOC, 2003, 68, 15-21

32. Bach, T. Nature, 2005, 436, 1139-1140

33. Bach, T. ACIE, 2009, 48, 1-4

34. Polymer-Bound Chiral Temple Bach, T. ACIE, 2008, 47, 7957-7959

35. 3.3 Chiral Sensitizer

36. Inoue JCS CC, 1993, 718 Schuster, JACS, 1990, 112, 9635 Photosensitized ant-Markovnikov methanol additiong to 1,1-diphenylpropene [4+2] cycloaddition between electron-rich diene and electron-rich dienophile

37. Sens* 2b : up to 70% ee Switching the product chiralty by solvent lower temperature higher ee The higheat ee ever reported for an enantiodifferentiating photosensitization. Inoue, JACS, 2000, 122, 406-407

38. Garcia, JOC, 2002, 67, 5184-5189

39. 3.3 Activation of Substates by Chiral Catalysts (Organocatalysis) Cordova, JACS, 2004, 126, 8914 ACIE, 2004, 43, 6532

40. MacMillan Science, 2008, 322, 77 JACS, 2009, 131, 10875

41. 4 Photecatalysts A: Via electron transfer

42. B: Via H abstraction

43. 5. Conclusion Solid-Phase asymmetric photochemistry can work very well, but has limited. Solution-phase photochemistry is more attractive for the catalytic enantiosele- ctive photochemistry. More excellent catalysts as Bach’ catalysts and assymme- tric inducing model will be developed. Asymmetric photochemistry using chiral sensitizers is usually poorly selective.