Synthesis of β-Vetivone More resources available ... - ChemistforChrist

Synthesis of β-Vetivone
The last step of the oxidation reaction with PCC we have already seen in the synthesis of JASMONE, here a little
reminder:
O
Thermodynamically more
stable due to being
a trisubstituted double
bond.
O
MeLi
Me
Jasmone
Synthesis of Posner JOC 1988, 53, 6031
MeO
O
S
O
O
MeTi(OiPr) 3
THF
Me CrO3, verd. H2SO4, Aceton
OH
Jones-Reagent
CrO 3
MeO
HO
Revisisiting: 1.4 Addition to chiral sulfoxides:
1.4 Addition to chiral sulfoxides:
µ O O
µ Decreasing Dipole-
R
S
Dipole interaction
R
O
S
R
O
Al (Hg)
created by reaction
of Al with HgCl 2
Chirality transfer on Carbon
OH
R
Al / Hg
O
S
O
S
Zn 2
O
OH
R
R
µ
Hydride
from above
O
R
S
O
µ
Cu-Organyl
will attack from
above!
R
DIBAL
ZnCl 2
O
O
S
tertiary alcohol,
H 2O is eliminated
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tertiary alcohol cannot be oxidized!
Me
O
S
O
Add metal
M = Zn, Ti
O
R
O
DIBAL
R
Raney-Nickel
EtOH
M
O O
S
Cu-Organyl
will attack from
below!
(Clayden, Greeves, Warren and Wothers, p.1266, reprint 2004, Oxford University press
O
S
Me
Me
O
O
51% yield
93% ee
Metal complexes
the oxygens and
attack leads to
the other isomer!
OH
R
Al / Hg
O R
S
O
Reduced
Dipol-Dipol
Interaction!
Hydride
from above
OH
R