Jasmone 1 - ChemistforChrist

Synthesis of JASMONE
one step
O
n-Bu Li
O
O
Li
Jasmone
Br
As discussed earlier not
a good E but used anyway
40%
(3 steps)
NaOH
Synthesis of Jasmone by Hiyama, Bull. Chem. Soc. Jpn. 1980, 53, 169-173
(Electrocylic reactions)
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www.chemistforchrist.de
O
1
O
2
3
AcOH,
H 2SO 4
H 2O
O
4
Problem: under the very acidic
hydrolysis condition E/Z isomerization
takes place! - 7% E Isomer is yielded
In an electrocyclic reaction a ring is always broken or formed. Rings may, of course be formed by cycloadditions
as well, but the difference with electrocyclic reactions is that just one new σ bond is formed (or broken) across
the ends of a single conjugated π system.
The types of pericyclic reactions are distinguished by the number of σ bonds made or broken.
Cycloadditions
2 new σ-bonds are formed
... or broken
∆σ = 2
Types of pericyclic reactions
Sigmatropic
rearrangements
One new σ-bonds is
formed as another is
broken.
∆σ = 0
Electrocyclic reactions
One new σ-bonds is formed
... or broken
∆σ = 1
Rules for electrocyclic reactions
All electrocyclic reactions are allowed
Thermal electrocyclic reactions involving (4n+2)π electrons are disrotatory:
one group rotates clockwise and one anticlockwise
Thermal electrocyclic reactions involving (4n)π electrons are conrotatory, in contrary reactions the two groups
rotate in the same way:
both clockwise both counterclockwise