Level 3 – Case 35
Solvolysis of Vinyl Iodonium Salts
Key point: Neighboring group participation.
Stereochemistry. Reactive intermediates
Ph
H
H
IPh
n-C 8 H 17
H
H
IPh BF 4
BF 4
solvolysis of
and
Solvolysis of Vinyl Iodonium Salts
The solvolysis in acetic acid (acetolysis) of E-styryl(phenyl)iodonium and E-1decenyl(phenyl)iodonium tetrafluoroborates 1 and 2 has resulted in a particular interest from a mechanistic point of view, as both substrates behave in a different
manner under the same conditions.
Ph
H
H
IPh
n-C 8 H 17
H
H
IPh BF 4
BF 4
1
2
Based on the following experimental data, discuss the mechanism of solvolysis of
1 and 2.
Experimental Data
Acetolysis of 1 yielded an 85:15 mixture of E/Z acetates
Z
3, together with iodobenzene and phenylacetylene, whereas acetolysis of 2 exclusively gave Z-alkene Z Z
4
and iodobenzene (Scheme 35.1). In addition, the acetolysis of 1 was two orders of
magnitude slower than that of 2.
Ph
H
H
IPh BF 4
AcOH
n-C 8 H 17
H
H
IPh BF 4
AcOH
Ph
H
H
OAc
n-C 8 H 17
H
OAc
H
PhI
Ph
H
OAc
H
PhC CH
PhI
1
2
3Z
4
E:Z (85:15)
Z
3E
Scheme 35.1