US EPA

1577615 

Journal Article 

Oxidative deprotection of oximes, phenylhydrazones and semicarbazones using pyridinium chlorochromate in catalytic amount with t-butyl hydroperoxide and in the solid state on montmorillonite K-10 clay support under microwave irradiation 

Ganguly, NC; Datta, M; De, P 

2004 

Yes 

Journal of the Indian Chemical Society
ISSN: 0019-4522 

81 

4 

308-312 

WOS:000223694100008 

Pyridinium chlorochromate (PCC) and other oxochromium (VI)
reagents have been extensively employed in excess of the stoichiometric amount (2 equivalents or
more) for efficient cleavage of oximes to carbonyl compounds. The aim of this study is to replace
excess use of toxic chromium (VI) reagents and develop cleaner environment-friendly general
methods of cleavage of imine derivatives such as oximes, phenylhydrazones and semicarbones using
PCC in catalytic or stoichiometric amount. Two approaches of greening the deprotection process
the PCC are conceived of which the first one is based on the catalytic use of the reagent (0.1
equiv.) in combination with an excess of 70% t-butyl hydroperoxide as the cooxidant. Mild
selective regeneration of carbonyl compounds from oximes, phenylhydrazones and semicarbazones has
been accomplished in good-to-excellent yields (70-98%) by this method. With focus on rate
enhancement coupled with efficiency of cleavage, an alternative microwave-assisted solid-state
solventless protocol of deprotection employing a stoichiometric amount of PCC dispersed on
montmorillonite K-10 clay is also evaluated. It offers an expeditious efficient (74-98% yields)
general route of cleavage of the procarbonyl compounds. Absence of overoxidation, particularly
for oxidation-prone aryl aldehydes, is the key advantage of both these methods.