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Synlett 2013; 24(4): 527-528
DOI: 10.1055/s-0032-1318134
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© Georg Thieme Verlag Stuttgart · New York

2,2,6,6-Tetramethylpiperidine-Based Oxoammonium Salts

Christopher B. Kelly
The University of Connecticut, Department of Chemistry, 55 North Eagleville Road, Storrs, CT 06269, USA   Email: Christopher.B.Kelly@uconn.edu
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Publication History

Publication Date:
18 January 2013 (online)

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Introduction

Oxoammonium salts have recently attracted much attention as environmentally friendly, shelf-stable alternatives to traditional oxidants.[ 1 ] In addition to being more sustainable, these salts have several advantages: 1) the spent ­oxidant is easily recovered and recyclable; 2) oxidations are performed under mild conditions and are simple to conduct; 3) oxidations are typically colorimetric processes and reaction progress can be monitored visually.[ 2 ]

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Scheme 1 Preparation of oxoammonium salts

Much of the work involving oxoammonium salts focusses on the conversion of alcohols into the corresponding carbonyl species.[3] [4] [5] [6] A range of functional groups can be ­accessed using this strategy including aldehydes,[ 2 ] carboxylic acids,[ 3 ] ketones (including the electron-deficient CF3 ketone)[ 6 ] and even esters.[ 5 ]

While highly effective for this type of transformation, several new applications for oxoammonium salts have been recently explored.[8] [9] [10] [11] These include several mechanistically interesting transformations such as exhaustive oxidation to give ene-triketones,[ 7 ] tandem dehydrogenative Povarov/oxidation reactions,[ 8 ] tandem α-alkylation/cyclization, α- and γ-alkylation of aldehydes,[ 9 ] and de­hydrogenative coupling of benzylic nitrogen/oxygen compounds with enolizable carbonyl groups.[ 10 ]