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OH
7
(1 mol %)
8
(20 mol %)
O
NHTs
NTs
9
(2 mol %)
toluene, air (1 atm), 100 °C, 18 h
13
14
O
O
O
NTs
Ts
NTs
14a
, 75%
14b
, 98%
14c
, 80%
O
O
O
NTs
NTs
NTs
Ts
O
O
PhN
14d
, 72%
14e
, 77%
14f
, 74%
14g
, 78%
a
O
NHTs
n
O
NHTs
N
Ts
n
14i
, n = 1, 89%
14j
, n = 4, 82%
O
14h
, 50%
a
7
(2 mol %),
8
(20 mol %)
9
(4 mol %), toluene, air (1 atm), 100°C, 24 h
Scheme 7.6 Three-component biomimetic oxidation of N-tosylamino alcohols.
N-protected amino alcohols using such a three-component biomimetic
oxidation process (Scheme 7.6).
16
Furthermore, benzo-fused seven-membered lactam 14h was successfully
isolated, albeit only in moderate yields. Conversely, N-tosylamino-1-hexanol
13i did not produce the expected simple seven-membered cyclic lactam. In
this case, the first oxidation step led to aminoaldehyde intermediate IIb
(Scheme 7.5), but the latter did not cyclize to form hemiaminal IIIb. Instead
intermolecular O-nucleophilc attack of Ib was observed, providing a hemi-
acetal intermediate which underwent the second oxidation step affording
dimer 14i. Similarly, b-lactams were not formed from substrate 13j, which
also produced dimer 14j.
Hirao and co-workers reported a heterogeneous biomimetic multicatalytic
process for the oxidation of secondary alcohols using water as a solvent
(Scheme 7.7).
17
Gold NPs supported on PMAS catalyzed the dehydrogenation
of alcohols; the polymer not only stabilized the Au NPs but also played the
role of a redox-active mediator (i.e. ETM and oxygen-activating). This
heterogeneous system can be reused for four runs without any significant
decrease in catalytic activity.
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