Phenyl selenide anion

Taber (42) and Kondo and co-workers (43) have found the stereospecific opening of J 2T + V22 with thiophenoxide. Using phenyl selenide anion as the reagent, Isobe and collaborators (44) discovered the conversion 123 124. 

Tetraethylammonium borohydride reduces diphenyl diselenide to phenylselenolate anion. When an acyl halide is added to the toluene solution of phenylselenolate anion, the corresponding acylation product is isolated in good yield (equation 4). Resin-supported phenyl selenide anion underwent acylation with acetyl chloride under mild reaction conditions. ... 

The Sn2 cleavage of esters and lactones is achieved with sodium phenyl selenide generated by the reaction between sodium hydride and benzene selenol, instead of the more usual sodium borohydride reduction of diphenyldiselenide. When generated under the former conditions the phenyl selenide anion is a potent nucleophile and good yields of seleno-acids are obtained from a wide range of esters and lactones (Scheme 3). ... 

In a range of anions PhZ (Z = O, S, Se, Te), for example, the thiophenolate ion (PhS ) effectively traps aryl radicals (Ar ), whereas the anion of phenyl selenide (PhSe ) is 20 times less active, and the phenolate anion (PhO ) is absolutely inactive. The reaction of aryl radicals with phenyl-telluride ions (PhTe ) proceeds in an abnormal fashion—both asymmetrical and symmetrical tellurides are produced (Rossi and Pierini 1980). 

Alternatively, the ambident oi-hetero substituted allyl anions have been utilized as homoenolate equivalents. For example, in the presence of HMPA, allyl phenyl sulfides (251),192 allyl phenyl sulfones (252)192b c and allyl phenyl selenides (253)192d e add to a,(3-enones in a l,4(0)-mode, while allyl phenyl sulfoxides (254) and allyl phosphine oxides (255) afford 1 A j-addition exclusively, irrespective of solvent used.193 Hua has shown that additions of either chiral sulfoxide (254 R1 = R2 = R3 = R4 = H, R5 = p-tolyl) or allyl oxazaphospholidine oxide (256) occur with excellent enantioselectivity (>95% ee).194 Similarly, Ahlbrecht reports that the a-azaallyl (257) adds exclusively in a 1 A j-mode to acceptor (59) to afford 1,5-diketones (Scheme 86).195... 

HomoallyUc alcohols. The anion (LDAi of ally I phenyl selenide reacts with a trialkylborane in THE at -78° to form an ate complex (a) which rearranges at 0° to the complex b. An allylic rearrangement of b to c occurs at 25°. Reaction of b with an... 

Epoxide opening by benzeneselenolate anion gave the rphenyl selenide with high regioselectivity (Table 8, entry 4)22. Oxidation and rearrangement yielded (+)- ra/t. -2-cyclohexene-1,4-diol. A similar approach was the key step in the synthesis of a ( + )-chorismate-prephenate analog (Table 8, entry 5)24. 

Treatment of benzylmethylphenylselenonium tetrafluoroborate with potassium r-butoxide gave a 9 1 mixture of methyl phenyl and benzyl phenyl selenides but no products which would have resulted had the appropriate ylide been formed (Scheme 66, a). This demonstrated that at least this salt is extremely susceptible to nucleophilic attack, even by nucleophiles as hindered as the r-butoxide anion (Scheme 66, a). ... 

The reaction of an aldehyde and benzeneselenol with gaseous hydrogen bromide in benzene in the presence of anhydrous calcium chloride results in an a-bromoalkyl phenyl selenide (1) in high yield. The corresponding anion reacts with aldehydes or ketones to form a Jj-hydroxy selenide (2). which can serve as a precursor to epoxides (6, 29) and olefins (6, 85-86). 

Photonucleophilic aromatic substitution reactions of phenyl selenide and telluride with haloarenes have also been proven to involve the S jlAr mechanism, with the formation of anion radical intermediates. Another photonucleophihc substitution, cyanomethylation, proves the presence of radical cations in the reaction mechanism. Liu and Weiss have reported that hydroxy and cyano substitution competes with photo substitution of fluorinated anisoles in aqueous solutions, where cation and anion radical intermediates have been shown to be the key factors for the nucleophilic substitution type. Rossi et al. have proposed the S j lAr mechanism for photonucleophihc substitution of carbanions and naphthox-ides to halo anisoles and l-iodonaphthalene. > An anion radical intermediate photonucleophilic substitution mechanism has been shown for the reactions of triphenyl(methyl)stannyl anion with halo arenes in liquid ammonia. Trimethylstannyl anion has been found to be more reactive than triphenylstannyl anion in the photostimulated electron- transfer initiation step. 

Recent examples of the rearrangement or alkynylation pathway include conversions of arylethynyl- and er -butylethynyl(phenyl)iodonium tosylates 24 and 25 to alkynylphosphonates, -selenides, and -tellurides with the appropriate anion salts in DMF (Scheme 50) [145-147], and a similar synthesis of push-pull selenides and tellurides from alkynyliodonium triflates containing electron-withdrawing groups in the alkynyl moiety [148]. 

Phenyl trimethylsilyi selenide benzeneselenol. The reaction of this anion, generated in. situ from diphenyl diselenide and sodium in THF, with chloro-trimethylsilane gives phenyl trimethylsilyi selenide in 72% yield..The product is sensitive to oxygen, but is stable under N2 indefinitely. It reacts rapidly with an alcohol to form benzeneselenol in high yield. 

Alkyl phenyl selenoxides bearing a P-hydrogen undergo facile syn elimination to form olefins under much milder conditions than the corresponding sulfoxides. The selenium anion formed from (PhSe)2 is an excellent nucleophile and easily opens the epoxide to give the corresponding hydroxyl selenide. This intermediate is not isolated but... 

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