Tetrahedron report number 892 Azobenzenesdsynthesis and carbohydrate applications Florian Hamon a , Florence Djedaini-Pilard b , Francis Barbot a , Christophe Len a, c, * a Universite´ de Poitiers, Synthe `se et Re ´activite ´ des Substances Naturelles, UMR CNRS 6514, 40 Avenue du Recteur Pineau, F-86022 Poitiers Cedex, France b Universite´ de Picardie Jules Verne, Laboratoire des Glucides, UMR CNRS 6219, 33 rue Saint Leu, F-80039 Amiens, France c Universite´ de Technologie de Compie`gne, Transformations Inte´gre ´es de la Matie`re Renouvelable, EA 4297 UTC/ESCOM,1 alle ´e du re ´seau Jean-Marie Buckmaster, F-60200 Compie`gne, France article info Article history: Received 7 August 2009 Available online 29 August 2009 Contents 1. Introduction .............................................................................................................................. 10105 2. Synthesis of azobenzene derivatives ....................................................................................................... 10107 2.1. Oxidation reactions of aromatic primary amines ..................................................................................... 10107 2.2. Reduction reactions of aromatic compounds having nitro groups ..................................................................... 10109 2.3. Coupling of primary arylamines with nitroso compounds (Mills reaction) ............................................................. 10110 2.4. Diazo-coupling via diazonium salts ................................................................................................. 10110 2.5. Oxidation of hydrazo derivatives .................................................................................................... 10113 2.6. Reduction of azoxybenzene derivatives .............................................................................................. 10113 2.7. Other methods ..................................................................................................................... 10115 3. Synthesis of azobenzene carbohydrates ..................................................................................................... 10116 3.1. Carbohydrate derivatives having one azobenzene moiety ............................................................................. 10116 3.2. Dimers and polymers linked with one azobenzene moiety ........................................................................... 10120 4. Conclusions .............................................................................................................................. 10121 Acknowledgements ....................................................................................................................... 10121 References and notes ...................................................................................................................... 10121 Biographical sketch ....................................................................................................................... 10123 1. Introduction Advances in molecular and supramolecular organization are a major challenge in organic chemistry. The control of molecular and supramolecular assembly may be obtained under ambient condi- tions by external inputs such as electricity, pH, redox potential, magnetic fields, and light. Various photochemical reactions are described in the literature: E/Z isomerization, tautomerization, electrocyclic reactions, heterolytic cleavage, and homolytic cleav- age. The use of light-powered reactions is the most reliable strategy to convert photochemical energy into reversible physical motion without waste (Fig. 1). Azobenzene derivatives have been used as photoresponsive functional devices utilized as smart polymers, 1 liquid crystals, 2 molecular switches, 3 and machines. 4 Azobenzene derivatives have received considerable experimental and theoretical attention. Azobenzene exists as two isomers: the isomer E (or trans) and the isomer Z (or cis) (Fig. 2). The E isomer is 50 kJ mol 1 more stable thermodynamically than the Z form. Consequently, the different spatial arrangements lead to different physical and chemical properties. The E to Z-photoisomerization of azobenzene induces a change of the dipole moment (m E-azobenzene¼0.5 D vs m Abbreviations: Ac, acetyl; BBCP, bis(2,2 0 -bipyridyl)copper(II) permanganate; Boc, tert-butoxycarbonyl; s-Bu, sec-Butyl; t-Bu, tert-butyl; Bz, benzoyl; CAN, cerium ammonium nitrate; CD, cyclodextrin; DCC, dicyclohexylcarbodiimide; DIB, diac- etoxyiodobenzene; DMF, dimethylformamide; DTBB, 4,4 0 -di-tert-butylbiphenyl; Et, ethyl; Fmoc, fluorenylmethyloxycarbonyl; HABA, 4-hydroxyazobenzene-2-carboxylic acid; HOBt, 1-hydroxybenzotriazole; Me, methyl; i-Pr, iso-Propyl; PTSA, para-tol- uenesulfonic acid; THF, tetrahydrofuran; p-Tol, para-tolyl; Tf, triflate; Ts, tosyl. * Corresponding author. Tel.: þ33 (0)5 49 36 63 89; fax: þ33 (0)5 49 45 37 02. E-mail address: christophe.len@utc.fr (C. Len). Contents lists available at ScienceDirect Tetrahedron journal homepage: www.elsevier.com/locate/tet 0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.tet.2009.08.063 Tetrahedron 65 (2009) 10105–10123 Contents lists available at ScienceDirect Tetrahedron journal homepage: www.elsevier.com/locate/tet