tempo and dichlorodicyanobenzoquinone

A mild and efficient oxidation of 3β-hydroxysteroids to the corresponding 3-keto steroids can be carried out at room temperature, using DDQ in the presence of catalytic TEMPO. Oxidation of saturated 3β-hydroxysteroids gave the corresponding ketones in excellent yield. The 5-unsaturated 3β-hydroxysteroids are oxidized selectively to 4-en-3-one or 4,6-diene-3-one derivatives according to the amount of DDQ in reaction. This is a good method for the synthesis of 4,6-diene-3-one from the corresponding 3β-hydroxy-5-ene steroids. Meanwhile, configurations of the oxidation compounds 2a, 2b, 3b, 2c, 2f and 2g were identified by X-ray diffraction. A possible mechanism is presented and discussed.

Topics: Benzoquinones; Cyclic N-Oxides; Hydroxysteroids; Temperature

Dimerization enthalpies and equilibrium constants have been determined for the radical anion of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), the radical cations of N,N,N',N'-tetramethyl-p-phenylenediamine, N,N-dimethyl-p-phenylenediamine, 2,3,5,6-tetramethyl-p-phenylenediamine, N,N,N',N'-tetraethyl-p-phenylenediamine, N,N-diethyl-p-phenylenediamine and N,N,N'-trimethyl-p-phenylenediamine. Neutral radicals investigated are 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and galvinoxyl. Solvent used was acetone, EtOH/Et2O-mixture (2:1 volume), propionitrile/butyronitrile-mixture (1:1 M) and dichloromethane. Measured dimerization enthalpies deltaHdim vary from -72.1 to -16.6 k/mol.

Topics: Acetone; Benzhydryl Compounds; Benzoquinones; Chemistry, Physical; Cyclic N-Oxides; Dimerization; Electron Spin Resonance Spectroscopy; Free Radicals; Methylene Chloride; Models, Statistical; Nitriles; Phenylenediamines; Temperature; Tetramethylphenylenediamine; Thermodynamics