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A new mild and efficient method for the deoxygenation of diarylmethanols is reported. The reaction employs catalytic hydrochloric acid in ethanol at reflux for 48 h. This reaction works on a variety of diarylmethanol substrates and mitigates the need for expensive and toxic reagents such stannanes and silanes used in alternative procedures. In addition, this reaction can be used in tandem with the deprotection of acid-sensitive silyl ether protecting groups in a one-pot procedure. Key words: deoxygenation, diarylmethanols, reduction, silyl ether deprotection. On rapporte une nouvelle meethode douce et efficace de desoxygenation des diarylmethanols. La reaction fait appel a une quantite catalytique d'acide chlorhydrique, dans l'ethanol au reflux, pendant 48 h. La reaction donne de bons resultats avec une variete de substrats diarylmethanols et elle atteenue le besoin pour des reactifs toxiques et dispendieux, tels les stannanes et les silanes utilises dans des meethodes alternatives. De plus, cette reaction peut etre utiliseee en tandem avec la deprotection d'ethers silyles sensibles aux acides utilises comme groupes protecteurs dans des methodes monotopes. Mots-cles: desoxygenation, diarylmethanols, reduction, deprotection d'eether silyle., Introduction Diarylmethane is a reoccuring structural motif in numerous natural products, including alangifolioside, (1) itoside K, (2) mastigophorene C, (3) and terrestrols F-H (4) (2-4, 5a-5c, Fig. 1). A possible [...]

A series of [C.sub.2]-symmetric compounds with different core sizes and varying lengths and numbers of alkoxy side chains were prepared, and the factors influencing their liquid crystalline mesophase behaviour were investigated. The compounds studied were based on benzophenone, dibenzylidene-acetone, and 1,9-diphenyl-nona-1,3,6,8-tetraen-5-one cores with either 1 or 2 linear alkoxy side chains. The side chains were varied in length from [C.sub.6][H.sub.13] to [C.sub.12][H.sub.25]. The liquid crystalline mesophase behaviour of the compounds was investigated using differential scanning calorimetry, polarizing optical microscopy, and small-angle X-ray scattering (SAXS). It was found that a number of the molecules were able to self-assemble into smectic and nematic liquid crystalline phases. Key words: mesophase, C2 symmetric, SAXS, benzophenone, dibenzylidene-acetone and 1,9-diphenyl-nona-1,3,6,8-tetraen5-one. On a realise la synthase d'une serie de composes de symetrie [C.sub.2] comportant des coeurs de tailles differentes et des quantites diverses de chaines laterales alcoxyles de longueurs variables et on a etudie les facteurs qui influencent leur comportement comme mesophase de cristal liquide. Les composesetudies ont des coeurs a base de benzophenone, de dibenzylideneacetone et de 1,9-diphenyl-1,3,6,8-tetraen-5-one et des chaines laterales alcoxyles lineeaires en positions 1 ou 2. Les longueurs de chaines laterales varient de [C.sub.6][H.sub.13] a [C.sub.12][H.sub.25]. On a etudie; leur comportement comme mesophase de cristal liquide en faisant appel a la calorimeetrie a balayage differentiel, a la microscopie optique polarisante et par la diffusion des rayons-X a angle faible (DXAF). On a trouve qu'un certain nombre de molecules peuvent s'autoassembler en phases de cristal liquide smectique et nematique. Mots-cles: mesophase, symetrie [C.sub.2,] diffusion des rayons X a angle faible (DXAF), benzophenone, dibenzylideneacetone, 1,9-diphenyl-1,3,6,8-tetraen-5-one. [Traduit par la Redaction], Introduction Liquid crystals are a growing field of research with applications in a wide variety of devices, including photovoltaic solar cells, (1) light-emitting diodes, (2) and displays. (3) Traditionally, molecules [...]

A new method for the preparation of peroxymonophosphoric acid ([H.sub.3]P[O.sub.5]) has been developed. It utilizes a biphasic solution to moderate the vigorous reaction between phosphorous pentoxide ([P.sub.2][O.sub.5]) and hydrogen peroxide ([H.sub.2][O.sub.2]). [P.sub.2][O.sub.5] is suspended in carbon tetrachloride (C[Cl.sub.4]), and concentrated [H.sub.2][O.sub.2] is slowly added while being vigorously stirred at low temperature. Careful control of the reaction temperature through the slow addition of [H.sub.2][O.sub.2] is critical. Using typical preparation conditions ([P.sub.2][O.sub.5]:[H.sub.2][O.sub.2] = 0.5:1, [H.sub.2][O.sub.2] 70 wt %, 2[degrees]C, 120-180 min), ~70% of the [H.sub.2][O.sub.2] is effectively converted to [H.sub.3P[O.sub.5]. Increasing the concentration of [H.sub.2][O.sub.2], as well as the mole ratio of [P.sub.2][O.sub.5]:[H.sub.2][O.sub.2], leads to an even higher % conversion of [H.sub.2][O.sub.2] to [H.sub.3]P[O.sub.5]. The addition of glacial acetic acid to the [P.sub.2][O.sub.5]:[H.sub.2][O.sub.2] suspension at the end of the 120-180 min reaction ([P.sub.2][O.sub.5]:[H.sub.2][O.sub.2]:C[H.sub.3]COOH = 0.5:1:0.3) leads to the formation of peracetic acid in addition to [H.sub.3]P[O.sub.5], and to an overall increase in the conversion ratio of total peroxy acids based on [H.sub.2][O.sub.2] (>95%). Key words: peroxymonophosphoric acid, synthesis, stability, conversion ratio.

Contrary to previous reports, the reaction mechanism of chlorine dioxide (OClO *) with benzyl alcohols involves both radical cation and benzyl radical mechanisms dependent on pH. The primary reaction product between OClO * and 1-(3,4-dimethoxy-phenyl) ethanol at pH 8 is 3,4-dimethoxyacetophenone. At pH 4 no acetophenone was observed; the majority of the degradation products were chlorinated and aromatic ring-oxidized compounds. A primary kinetic isotope effect ([k.sub.H]/[k.sub.D] = 2.05) was observed in the reaction of OClO * with 1-(3,4-dimethoxy-phenyl)-([1.sup.-2]H) ethanol at pH 8, but was absent at pH 4 ([k.sub.H]/[k.sub.D] [approximately equal to] 1). Similarly, the corresponding methyl ether (4-(1-methoxy)ethyl-1,2- dimethoxybenzene) was substantially less reactive at pH > 6. On the basis of these results, competing pH-dependent reaction mechanisms have been proposed, where at high pH OClO * reacts with benzyl alcohols via a OClO *-benzyl alcohol complex. Key words: chlorine dioxide, mechanism, kinetic isotope effect, aromatic radical cation, benzyl radical.

Thermal decomposition of bis(perfluoro-2-N-propoxyprionyl) peroxide in dense carbon dioxide and fluorinated solvents was studied.