Issue 3, 2013
From the journal:

Organic & Biomolecular Chemistry

A mechanistic study on the Hooker oxidation: synthesis of novel indanecarboxylic acid derivatives from lapachol†

Kenneth O. Eyong,ab   Manohar Puppala,a   Ponminor Senthil Kumar,a   Marc Lamshöft,c   Gabriel N. Folefoc,*b   Michael Spiteller*c  and  Sundarababu Baskaran*a  

* Corresponding authors

a Department of Chemistry, Indian Institute of Technology Madras, Chennai, India
E-mail: sbhaskar@iitm.ac.in
Fax: (+91) 44-2257-0545

b Department of Organic Chemistry, University of Yaounde 1, BP 812 Yaounde, Cameroon

c Institute of Environmental Research and Analytical Chemistry, Dortmund University of Technology, 44227 Dortmund, Germany

Abstract

The Hooker oxidation is one of the most intriguing transformations wherein lapachol (1) is readily converted to norlapachol (2) in very good yield. This one-pot reaction involves a very intricate mechanism in which the alkyl side chain of lapachol is shortened by one carbon unit. Previous studies have unequivocally established the involvement of an indane carboxylic acid derivative 3, as a key intermediate (Hooker intermediate), and its simultaneous conversion to norlapachol (2) via the oxidative cleavage of vicinol diol and subsequent intramolecular aldol reaction of the resulting keto acid. However, the formation of the key Hooker intermediate 3 from lapachol (1) remains ambiguous. The present study has thrown some light on the formation of the key intermediate 3 from lapachol (1) via benzilic acid rearrangement of the corresponding labile o-diquinone intermediate 8 derived from lapachol. The involvement of o-diquinone intermediate 8 in the Hooker oxidation has been further established by trapping of this labile intermediate as the corresponding phenazine derivative 9. The involvement of benzilic acid rearrangement as a key step in the Hooker oxidation is further shown with a variety of o-quinones prepared from lapachol (1).

Graphical abstract: A mechanistic study on the Hooker oxidation: synthesis of novel indane carboxylic acid derivatives from lapachol

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Article information

DOI
https://doi.org/10.1039/C2OB26737C
Article type
Paper
Submitted
04 Sep 2012
Accepted
07 Nov 2012
First published
07 Nov 2012

Org. Biomol. Chem., 2013,11, 459-468

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A mechanistic study on the Hooker oxidation: synthesis of novel indane carboxylic acid derivatives from lapachol

K. O. Eyong, M. Puppala, P. S. Kumar, M. Lamshöft, G. N. Folefoc, M. Spiteller and S. Baskaran, Org. Biomol. Chem., 2013, 11, 459 DOI: 10.1039/C2OB26737C

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