Selenides, 3-hydroxy phenyl

An alternative approach is to use the readily available P-hydroxy phenyl selenides as Ritter substrates. Amide formation occurs with retention of configuration, indicating that fission of the carbon-oxygen bond is assisted by the neighboring phenylseleno group (Scheme 61). Diphenyl diselenide and iodine react with 1,5-dienes to give carbocyclic products. Initial formation of the episelenonium ion is followed by intramolecular attack and subsequent Ritter reaction (Scheme 62). ... 

Formation of CK-configurated cyclobutanones has also been observed with 2-methylcyclopen-tanone and 2-methylcyclohexanone/8 However, stereoreversed eyclobutanone formation can be achieved by opening the intermediate oxaspiropentane with sodium phenyl selenide, oxidation of the resulting / -hydroxy selenide with 3-chloroperoxybenzoic acid and subsequent rearrangement in the presence of pyridine/18 Thus, from one oxaspiropentane 8, either stereoisomeric eyclobutanone cis- or lrans-9 was produced. The stereoreversed eyclobutanone formation proceeds from a stereohomogenous / -hydroxy selenoxide and is thought to be conformationally controlled. 

Diisobutylaluminum phenyl selenide, 117 Triphenyltin hydride, 335 Hydroxy sulfur compounds Diisobutylaluminum hydride, 115 Methylthiomethyllithium, 192 Thiophenol, 53, 312... 

Bipheny]yl)- E2, 838 5-Hydroxy- -5-oxid XII/1, 240 5-(Methy]-phenyl-iminio)-5-phenyl- E2, 889 5-Phenyl- E2, 892 5-Phenyl- -9-selenid E2, 93... 

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. 

The stereospecific conversion of cyclohexene into the corresponding amido selenide 54 is illustrated in Scheme 8. These amidoselenenylation reactions are commonly employed for the preparation of allylic and saturated amides by oxidative or reductive deselenenylation. Propionitrile, butyronitrile, benzonitrile and ethyl cyanoacetate may be used in place of acetonitrile. Styrene gave poor results and other electron-rich olefins such as 1-methylcyclohexene or 2,3-di-methylbut-2-ene did not give the amidoselenenylation products. The reaction can also be effected starting from the hydroxy- or methoxyselenenylation products of alkenes, in the presence of water and trifluoromethanesulfonic acid in this case the nitriles are used in stoichiometric amounts [48c]. This methodology was employed to prepare the amidoselenenylation products of styrene, 55, and of electron-rich olefins. It was necessary, however, to replace the phenyl-... 

The reaction involving the alkylation of p-hydroxyalkyl selenides to give p-hydroxyalkylselenonium salts which are then cyclized with a base is by far the most general. It allows Ae synthesis of a large variety of epoxides such as tenninal, a,a- and a,p-disubstituted, tri-33-> and tetra-substituted, 3,i88 as oxaspiro[2.0.n]-hexanes, -heptanes and -octanes (Scheme 161, g Scheme 162, d Scheme 164, d Scheme 165, b) - and vinyl oxiranes (Schemes 166 and 181)33 -239 from both p-hydroxy-alkyl methyl33- 3 3 22>.222j36,263 phenyl selenides. ... 

Sion of j3-hydroxy selenides (1) into olefins. The starting materials are generally prepared from alkyl phenyl selenides, readily available by reaction of tosylatcs. 

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). 

Di-(2-hydroxy-2-propylphenyl) selenide gives the selenurane analogue (45a CH, in place of CF H in place of Bu ) of the sulphurane (45a) through a simple procedure (Brz followed by EtjN). Easy access to higher valency states for selenium derivatives may account for some differences in properties of bivalent sulphur compounds compared with their selenium analogues for example, phenyl vinyl selenide PhSeCH=CH2 does not polymerize with benzoyl peroxide, as does the vinyl sulphide, but gives the dibenzoate PhSeCH(OCOPh)CH2(OCOPh) via the selenurane PhSe-(OCOPh)2CH=CH2. ... 

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. 

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