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12.9.6 Other organic secondary oxidants
Trichlorocyanuric acid (TCCA)
110,171
and
N
-chlorosuccinimide (NCS)
69
have also been used as secondary
oxidants. The selectivity of the TEMPO-catalyzed reactions are generally preserved, and these reagents
were successfully applied toward the synthesis of multifunctional molecules (Schemes 12.37,
172
12.38,
173
and 12.39
174
). One advantage of these reactions is that the oxidant is a solid and a more careful stoi-
chiometric control over the oxidation can be achieved than, for instance, when using bleach. They can be
used in pure organic solvents or in buffered aqueous/organic solvent mixtures. Their disadvantages include
OH
OH
O
O
O
O
TEMPO (cat.), TCCA,
CH
2
Cl
2
, 25
°
C, 1 h
O
O
NC
NC
CHO
OH
(85 %)
Scheme 12.37
OTBS
OTBS
CHO
OH
TEMPO (cat.), NCS, Bu
4
NCl,
CH
2
Cl
2
, H
2
O, buffer, pH 8.6
OH
OH
O
O
O
O
(95 %)
Scheme 12.38
OH
OH
O
O
O
O
TEMPO (cat.), NCS, Bu
4
NCl,
CH
2
Cl
2
, H
2
O, buffer, pH 8.6, 25
°
C
O
O
O
O
OH
CHO
O
O
O
O
OTBS
O
O
O
O
OTBS
(88 %)
Scheme 12.39
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