123.202 alkenes

1. LECTURE SEVEN
alkenes ©mugley@flickr

2. hyd rogenation
of alkenes
H2
Pd/C H
H
syn
addition

3. ©Oberazzi@flickr

4. surface
reaction
H
H H H H H

5. surface
reaction
H
H H H H H

6. surface
reaction
H
H H H H H
H
delivered from
same face

7. ©e-magic@flickr

8. importance
of
stereochemistry
?
H2
Pd/C
?
H2
Pd/C

9. importance of stereochemistry
H2 H H
Pd/C
Z-alkene
meso
cis
achiral

10. importance of stereochemistry
H2 H H
Pd/C
E-alkene
chiral
trans

11. example
O
O
H
O
O OMe
OH
O O
OH
resiniferatoxin
©VT Jenny@Horticulture in the desert

12. example
O
O
H
O
O OMe
OH
O O
OH
resiniferatoxin
1000x

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. hyd rogenation
of alkynes
H2 H
Pd/C H
H H
full
reduction

15. partial Z-alkene
reduction
cis
H2
Lindlar
catalyst H H
syn
addition

16. ©wonderferret@flickr

17. catalyst
poisoning
Pd/CaCO3/Pb
©Grant and Caroline@flickr

18. partial E-alkene
reduction
trans
Na
NH3(l) H
H
anti
addition

19. ©carbonNYC@flickr

20. Na NH3 Na e [NH3]n
©P.P.Edwards@Oxford University

21. mechanism
e
H NH2
H H
e
H NH2
H radical
permits
H isomerisation

22. S
HO N
O
O OH O
epothilone C
example

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. hydrohalogenation & acid-catalysed
hydration
X
H X
H

25. step 1
H X H X
nucleophile step 2
electrophile
X
mechanism H

26. H step 1 H
H O H O
H H
nucleophile
step 2
electrophile
H H
O
mechanism H

27. H step 1 H
H O H O
H H
step 2
H O H H
O H H O
H H

28. remember
electrons
©Aidan O'Sullivan@flickr
attack δ+ or +