Zink Organyle

1. Metallorganische Chemie 1 Zink Organyle Frankland 2 RI + 2 Zn -> R2Zn + ZnI2 Reformatsky Reagenz Simmons-Smith Reaktion 1984 Oguni asymmetrische Addition

2. Metallorganische Chemie 2 Reformatzky Reaktion

3. Metallorganische Chemie 3 Reformatsky Reagenz

4. Metallorganische Chemie 4 Reformatsky Reagenz

5. Metallorganische Chemie 5 Homo-Reformatsky Reagenz

6. Metallorganische Chemie 6 Homo-Reformatsky Reagenz

7. Metallorganische Chemie 7 Simmons-Smith

8. Metallorganische Chemie 8 Alkenaffinit�t von Zn-Organylen Paul Knochel Tet. Lett 1986, 27, 1039Paul Knochel Tet. Lett 1986, 27, 1039

9. Metallorganische Chemie 9 Simmons-Smith Reagenz

10. Metallorganische Chemie 10 Furukawa Reaktionen

11. Metallorganische Chemie 11 Simmons-Smith Reaktionen

12. Metallorganische Chemie 12 Stereoselektive Cyclopropanierung Substrate controlled: I. Arai, H. Yamamoto JACS 1985, 107, 8254, Tetrahedron 1986, 42, 6447 Reagent controlled: A.B. Charette JOC 1995, 60, 1081Substrate controlled: I. Arai, H. Yamamoto JACS 1985, 107, 8254, Tetrahedron 1986, 42, 6447 Reagent controlled: A.B. Charette JOC 1995, 60, 1081

13. Metallorganische Chemie 13 Oguni asymmetrische Addition

14. Metallorganische Chemie 14 Knochels asymmetrische Addition

15. Metallorganische Chemie 15 Asymmetrische Autokatalyse Soai K. et al Nature 1995, 378, 767Soai K. et al Nature 1995, 378, 767

16. Metallorganische Chemie 16 Asymmetrische Autokatalyse Soai K. et al Nature 1995, 378, 767Soai K. et al Nature 1995, 378, 767

17. Metallorganische Chemie 17 Enantioselektive Addition Soai K. et al Nature 1995, 378, 767Soai K. et al Nature 1995, 378, 767

18. Metallorganische Chemie 18 Transmetallierung Zn-Organyle

19. Metallorganische Chemie 19 Wo geht es weiter? Basisch Lewis S�ure Li Be Na Mg B K Ca Ti Al Si Ni Cu Zn In Cs Ba Pd Sn

20. Metallorganische Chemie 20 Indium

21. Metallorganische Chemie 21 Indium Vorteile

22. Metallorganische Chemie 22 Indium Vorteile

23. Metallorganische Chemie 23 Barbier Allylierung

24. Metallorganische Chemie 24 Allylierung von Ketonen L�semittelfrei In polar protischen L�sungsmitteln

25. Metallorganische Chemie 25 a- versus g-Angriff

26. Metallorganische Chemie 26 Stereoselektive Allylierung

27. Metallorganische Chemie 27 Diastereoselektivit�t

28. Metallorganische Chemie 28 Stereoselektivit�t The Cram chelate model predicts the stereochemical course of organometallic additions to �-alkoxy carbonyl compounds based on a complexation of the metal by the chelating oxygen. Would this ligation persist in the presence of competing water? Paquette et al. investigated this problem thorougly and found that in fact water was the solvent, which led to the best results. Scheme 9 shows the allyl addition to 3-hydroxybutanal which gave the anti-product in a 8.5:1 ratio when water was used as a solvent while no reaction occurred in water-free THF. Similar results were obtained with protected hydroxy groups although selectivities were significantly lower in these cases, especially with bulky protecting groups. The high anti-selectivity could be explained by a Zimmerman�Traxler-like transition state, with additional complexation of indium by the oxygen of the hydroxy function. In this case the allyl moiety attacks from the less hindered side, opposite to the methyl group (Scheme 9).The Cram chelate model predicts the stereochemical course of organometallic additions to �-alkoxy carbonyl compounds based on a complexation of the metal by the chelating oxygen. Would this ligation persist in the presence of competing water? Paquette et al. investigated this problem thorougly and found that in fact water was the solvent, which led to the best results. Scheme 9 shows the allyl addition to 3-hydroxybutanal which gave the anti-product in a 8.5:1 ratio when water was used as a solvent while no reaction occurred in water-free THF. Similar results were obtained with protected hydroxy groups although selectivities were significantly lower in these cases, especially with bulky protecting groups. The high anti-selectivity could be explained by a Zimmerman�Traxler-like transition state, with additional complexation of indium by the oxygen of the hydroxy function. In this case the allyl moiety attacks from the less hindered side, opposite to the methyl group (Scheme 9).

29. Metallorganische Chemie 29 Stereoselektivit�t Similar transition states explain the preferential formation of the syn-product in the allyl addition to a-hydroxy aldehydes. Nevertheless, for more sterically demanding substrates and especially with substituted allyl compounds, the minor anti-product is possibly formed via an open-chain transition state rather than via chelate control. The probable chelation should similarly account for a-thio and a-amino aldehydes.Similar transition states explain the preferential formation of the syn-product in the allyl addition to a-hydroxy aldehydes. Nevertheless, for more sterically demanding substrates and especially with substituted allyl compounds, the minor anti-product is possibly formed via an open-chain transition state rather than via chelate control. The probable chelation should similarly account for a-thio and a-amino aldehydes.

30. Metallorganische Chemie 30 Stereoselektivit�t

31. Metallorganische Chemie 31 Indium: katalytisch

32. Metallorganische Chemie 32 Indium: katalytisch

33. Metallorganische Chemie 33 Barbier: enantioselektiv

34. Metallorganische Chemie 34 Indium: Nitro-Reduktion

35. Metallorganische Chemie 35 Zinn TBTH Tributylzinnhydrid R3Sn-X

36. Metallorganische Chemie 36 Toxizit�t LD50 mg/kg Ratte R R3SnCl R2SnCl2 RSnCl3 Me <20 <230 <1350 Bu <350 <220 <2200 Ph <135 / /

37. Metallorganische Chemie 37 Lipophil Bu3SnCl ist l�slich in Hexan und unl�slich in MeCN Bu3SnBr/I TLC rf Hexan ca 0.9

38. Metallorganische Chemie 38 R3Sn Anion

39. Metallorganische Chemie 39 R3Sn Anion

40. Metallorganische Chemie 40 Reaktivit�t Oxidation Fragmentierung

41. Metallorganische Chemie 41 �Grob�-Fragmentierung

42. Metallorganische Chemie 42 Maskierte Acylanionen

43. Metallorganische Chemie 43 Maskierte Acylanionen