Chemistry Reference
In-Depth Information
SCHEME 4.14.
Hydrolysis of pivalic acid esters of
N
-arylydroxylamines.
tert
-butyl radical under these conditions.
95
Since no rearrangement product was
observed, it was tentatively concluded that this ester undergoes direct decomposition
to 4-nitrophenyl nitrene without the intermediacy of a nitrenium ion.
95
An alternative
explanation is rate limiting generation of the ion pair that undergoes rapid depro-
tonation to the nitrene.
Esters
were reduced to the corresponding amine by Fe
2
þ
.
95,96
Rate
accelerations of 10
4
in 1 mM Fe
2
þ
precluded a nitrenium ion mechanism.
96
The
reaction produced pivalic acid and was hindered by complexation of Fe
2
þ
by CN
.
95
Reduction was promoted more effectively by Cu
þ
than by Fe
2
þ
, and
N
-arylhydroxyl-
amines added to the mixture were oxidized to nitroso compounds, apparently by
single electron transfer from an arylamino radical or radical cation.
96
A single
electron transfer from Fe
2
þ
to the ester within a complex was proposed.
95,96
The
resulting arylamino radical or its conjugate acid could be reduced to the amine by
Fe
2
þ
or other species capable of electron or H-transfer.
N
-Acylated esters do not
61a-d
