123.202 Lecture 7 - alkenes

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123.202 alkenes

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123.202 Lecture 7 - alkenes

  1. 1. LECTURE SEVEN alkenes ©mugley@flickr
  2. 2. hyd rogenation of alkenes H2 Pd/C H H syn addition
  3. 3. ©Oberazzi@flickr
  4. 4. surface reaction H H H H H H
  5. 5. surface reaction H H H H H H
  6. 6. surface reaction H H H H H H H delivered from same face
  7. 7. ©e-magic@flickr
  8. 8. importance of stereochemistry ? H2 Pd/C ? H2 Pd/C
  9. 9. importance of stereochemistry H2 H H Pd/C Z-alkene meso cis achiral
  10. 10. importance of stereochemistry H2 H H Pd/C E-alkene chiral trans
  11. 11. example O O H O O OMe OH O O OH resiniferatoxin ©VT Jenny@Horticulture in the desert
  12. 12. example O O H O O OMe OH O O OH resiniferatoxin 1000x
  13. 13. example OAc OAc OBn H2 OBn 10% Pd/C H H O O O 99% O OTBS OTBS H H H H H H O O H O O OMe OH O O resiniferatoxin OH J. Am. Chem. Soc., 1997, 119, 12976
  14. 14. hyd rogenation of alkynes H2 H Pd/C H H H full reduction
  15. 15. partial Z-alkene reduction cis H2 Lindlar catalyst H H syn addition
  16. 16. ©wonderferret@flickr
  17. 17. catalyst poisoning Pd/CaCO3/Pb ©Grant and Caroline@flickr
  18. 18. partial E-alkene reduction trans Na NH3(l) H H anti addition
  19. 19. ©carbonNYC@flickr
  20. 20. Na NH3 Na e [NH3]n ©P.P.Edwards@Oxford University
  21. 21. mechanism e H NH2 H H e H NH2 H radical permits H isomerisation
  22. 22. S HO N O O OH O epothilone C example
  23. 23. S TBSO N O O OTBS O i. H2, Lindlar cat. ii. HF (79%) H H S HO N O O OH O
  24. 24. hydrohalogenation & acid-catalysed hydration X H X H
  25. 25. step 1 H X H X nucleophile step 2 electrophile X mechanism H
  26. 26. H step 1 H H O H O H H nucleophile step 2 electrophile H H O mechanism H
  27. 27. H step 1 H H O H O H H step 2 H O H H O H H O H H
  28. 28. remember electrons ©Aidan O'Sullivan@flickr attack δ+ or +

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