Synthesis and reactivity of alpha-phenylseleno-beta-substituted styrenes: preparation of (Z)-allyl alcohols, (E)-alpha-phenyl-alpha,beta-unsaturated aldehydes and alpha-aryl acetophenones

Abstract

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...

(Z,Z)-Selanediylbis(2-propenamides): Novel Class of Organoselenium Compounds with High Glutathione Peroxidase-Like Activity. Regio- and Stereoselective Reaction of Sodium Selenide with 3-Trimethylsilyl-2-propynamides

“…Vinyl selenides are important intermediates for organic synthesis [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ]. These compounds have been used for the preparation of a number of valuable products [ 4 , 5 , 6 , 7 , 8 , 9 ]. Vinyl selenides have found application in the synthesis of functionalized ketones, ( Z )-allyl alcohols, and unsaturated aldehydes [ 4 ].…”

Synthesis of 2,2‐diarylvinyl phenyl selenides by dehydration of 2‐hydroxyalkyl phenyl selenides

“…To a far less extent, functionalization of the vinylic chalcogen analogues, that is, non‐saturated phenyl vinyl selenides, have been investigated despite their potential applications in construction of versatile ethylene derivatives and vinyl synthons . Vinyl selenides have been prepared utilizing mercury reagents in stoichiometric quantities, by heavy metal cross‐coupling such as carboselenation involving unavailable precursors or via complex pre‐synthetic steps . In search for general access to vinyl selenide synthons from more readily available precursors, it was envisioned that phenyl vinyl selenides would form upon dehydration of 2‐hydroalkyl phenyl selenides.…”

Water-Dependent Selective Synthesis of Mono- or Bis-Selanyl Alkenes from Terminal Alkynes

“…An interesting class of selenium compounds are the selanyl alkenes, which exhibit pharmacological properties and are versatile intermediates in organic synthesis . They can be converted to ( E )‐ and ( Z )‐alkenes with total control in the stereochemistry of the double bond via Se−Li transmetalation or the iron‐catalyzed coupling with Grignard reagents . Besides, selanyl alkenes are easily hydrolyzed to ketones under mild reaction conditions .…”

“…They can be converted to ( E )‐ and ( Z )‐alkenes with total control in the stereochemistry of the double bond via Se−Li transmetalation or the iron‐catalyzed coupling with Grignard reagents . Besides, selanyl alkenes are easily hydrolyzed to ketones under mild reaction conditions . In view of the importance of selanyl alkenes, several procedures for their preparation have been described and the most common and atom‐economic protocols involve the addition of organoselenols, or the respective selenolate anions generated in situ, to alkynes…”