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Diaryl, dialkyl and alkyl aryl sulfides are oxidized by cerium (IV) ammonium nitrate in H2 O/CH 2 Cl 2, in the presence of tetra-n-butylammonium bromide, at room temperature, to give sulfoxides in yields ranging between 90 and 100%.

Les reactions du titre sont realisees sous diverses conditions: a) reaction avec le nitrate d'ammonium cerique (CAN) dans l'acide acetique et l'acetonitrile aqueux ; b) oxydation electrochimique dans l'acetone aqueuse et dans AcOH−CH 3 CN ; c) autooxydation photochimique en presence d'anthracenedicarbonitrile-9,10 ou CAN dans CH 3 CN ; d) oxydation photochimique par CAN dans CH 3 CN

Les β-eliminations syn et anti a partir d'une serie de 31 dihalogeno-2,3 dihydro-2,3 benzofurannes sont etudiees du point de vue cinetique dans t-BuOK-t-BuOH, en presence et en l'absence de 18-crown-6, et dans EtOK-EtOH

Addition d'acetone, butanone-2, methyl-3 butanone-2, acetylacetate d'ethyle au butadiene-1,3. Obtention de composes d'addition 1,2 et 1,4

Aromatic compounds undergo homolytic malonylation by reaction with cerium(IV) ammonium nitrate and dimethyl malonate in methanol at room temperature.

1,4-diketones and 4-ketoaldehydes dimethylacetals can be prepared in good yields (65%–82%) by the cerium(IV) ammonium nitrate promoted reaction of ketones with isopropenyl acetate and vinyl acetate, respectively.

"Isoretinolq I was prepd. in 55% yield by methylation of II, obtained by reaction of III with the (chlorodihydrofuryl)copper IV. Oxidn. of I with Me2SO contg. N,N'-dicyclohexylcarbodiimide gave a stereoisomeric mixt. of retinal. Similarly, Me2C:CHCH2CH2CMe:CHCH:C:CMeCH2CH2OH was prepd. from geranyl bromide and IV and oxidized to give 4,5-dehydrofarnesal, Me2C:CHCH2CH2CMe:CHCH:CHCMe:CHCHO, which was reduced to give 4,5-dehydrofarnesol, Me2C:CHCH2CH2CMe:CHCH:CHCMe:CHCH2OH. [on SciFinder (R)]

1,4-diketones and 4-ketoaldehydes dimethylacetals can be prepared in good yields (65%–82%) by the cerium(IV) ammonium nitrate promoted reaction of ketones with isopropenyl acetate and vinyl acetate, respectively.

The torsional barriers of 2'-substituted 2-arylpyridines have been probed experimentally (by using dynamic NMR spectroscopy) and computationally (by using density functional theory). Due to the compressibility of the lone pair, the torsional barriers of the arylpyridines are up to 4.2 kcal/mol smaller than those of the carba-analogous biphenyls. Furthermore, the ground states of the 2-arylpyridines are less twisted than those of the biphenyls. Finally, due to an out-of-collinearity distortion, the intramolecular repulsion is attenuated in both rotational transition states, in the syn coplanar conformer (in which the pyridine nitrogen and the substituent R face each other) and in the anti coplanar conformer (in which they are on opposite sides of the molecule).

Novel planar chiral N,O-ligands derived from (R)-(+)-and (S)-(-)-2,4-dimethyl[2]paracyclo[2](5,8)quinolinophane were synthesized and employed as catalyst in the enantioselective addition of diethylzinc to aromatic aldehydes. On the basis of the ee values, ranging from 30% to 75%, and the configuration of the obtained 1-phenyl-1-propanols a plausible structure of the transition state for the alkylation process of the aldehydes is discussed.

Rate ratios were obtained for the base-catalyzed 1,4-dehydrochlorination of (E)- and (Z)-Me3CCCl:C:C:CClCMe3 to give Me3CC.tplbond.CC.tplbond.CCMe3. In the KOMe/MeOH or KOCMe3/Me2SO systems the reactivity of both isomers was similar. With KOCMe3 in Me3COH, THF or C6H6 the 2 isomers exhibited similar reactivity when 18-crown-6 was present, but the E isomer was much more reactive in its absence. These findings suggested a conveyor-belt-type transition state with an aggregate of the base interacting with the H and Cl atoms undergoing elimination. [on SciFinder (R)]

Treatment of the title compound with chloride ions in acetonitrile leads mainly to the formation of trans-2,3-dichloro-2,3-dihydrobenzofuran. Since a nucleophilic displacement of bromide anion by chloride anion can be excluded, a mechanism involving the equilibrium 2Cl− + Br2 ⇋ 2Br− + Cl2 is suggested.

The lack of a significant leaving group effect and the preferential departure of the ‘poorer’ leaving group suggest an irreversible E1cb mechanism for the title reactions.

The oxidation of 1,2- diphenylethane and 2,3-dimethyl-2,3-diphenylbutane by cerium(IV) ammonium nitrate and Co(OAc)3 in acetic acid show that a radical cation mechanism is plausible only in the reaction of the former oxidant.