Foi desenvolvido um método simples e eficiente para a síntese de β-estirenos α-fenilselenosubstituídos, através da reação do α-(fenilselenobenzil)fosfonato de dietila e NaH na presença de aldeídos. A reação destes produtos com n-BuLi e posterior captura do ânion com aldeídos ou DMF levou à formação, exclusivamente, de álcoois de configuração Z e aldeídos α,β-insaturados de configuração E, respectivamente. Além disto, a hidrólise dos selenetos na presença de TiCl 4 levou à formação de α-arilacetofenonas em bons rendimentos.A new and efficient method was developed to prepare α-phenylseleno-β-substituted styrenes by reaction of diethyl α-phenylseleno benzylphosphonate with NaH and aldehydes. Seleniumlithium exchange by reaction with n-BuLi yielded the vinyl lithium species, which were captured with several electrophiles, like aldehydes and DMF, affording exclusively (Z)-allyl alcohols, and (E)-α-phenyl-α-β-unsaturated aldehydes, respectively in good yields. The hydrolysis of the vinyl selenides in presence of TiCl 4 allowed the corresponding α-aryl acetophenones.Keywords: Horner-Wittig reactions, vinyl selenides, transmetallation, α-β-unsaturated aldehydes, Z-allyl alcohols IntroductionOrganoselenium compounds constitute useful intermediates in organic synthesis and much attention has been devoted to their preparation and synthetic utilization. 1 Among the different classes of these compounds, vinyl selenides constitute a very useful intermediate, because of the versatile reactivity of the selanyl group and the presence of carbon-carbon double bond. 2 Considerable efforts have been directed to preparation of vinyl chalcogenides by the Wittig-type reaction, including the synthesis of vinyl selenides diand trisubstituted by Wittig 3,4 and Horner-Wittig reaction. 5,6 An interesting aspect of this approach is the possibility to synthesize vinyl selenides with homologation of the carbon skeleton. 7 To the best of our knowledge, the only methods reported for the preparation of α-phenylseleno-β-substituted styrenes involve the reaction of Z-α-(phenylseleno)vinyl p-toluensulfonates with Ph 2 Cu(CN)Li 2 in presence of catalytic amounts of Pd(PPh 3 ) 2 Cl 2 (only three examples) 8 and the hydroselenation of phenylacetylene using aluminum phenylselenolate anion (one example), 9 while the Wittig-type reaction have not been considered as a general synthetic strategy to date. Recently, we have described practical and utile methodologies for the preparation of vinyl sulfides, 10 selenides, 10,11 tellurides, 10,12 ketene telluroacetals, 13,14 ketene (Te,S)-acetals 15 and α-phenyltelluro-and α-phenylseleno acrylonitriles 16 based on Wittig-type reactions. Due to our continuous interest on the synthesis and reactivity of new vinyl chalcogenides, 17 we report here the application of the Horner-Wittig reaction to the synthesis of α-phenylseleno-β-substituted styrenes 6 (Scheme 1, Table 1). The Se/Li exchange followed by capture of the intermediate vinyl lithium with electrophiles, and the hydrolysis of some obtained vinyl selenides ar...
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