Selenoxides diphenyl selenoxide

No oxidizing agent is required for the sulfuric acid promoted cyclization of iV,iV-diphenyl-hydroxylamine to carbazole (13CB3304). The parallel conversion of diphenyl sulfoxide and diphenyl selenoxide to dibenzothiophene (23CB2275) and dibenzoselenophene (39CR(199)53l) is effected by treatment with sodamide. 

This reaction depends upon the facile solvolysis of (J-haloselenides and the facile oxidative elimination of a selenoxide, which was discussed in Section 6.6.3. An alternative method, which is experimentally simpler, involves reaction of alkenes with a mixture of diphenyl diselenide and phenylseleninic acid.189 The two selenium reagents generate an electrophilic selenium species, phenylselenenic acid, PhSeOH. 

DIHYDROXYLATION Osmium tetroxide-Dihydroquinine acetate. Osmium tetrox-ide-Diphenyl selenoxide. Osmium tetroxide-Trimethylamine N-oxide-Pyiidine. Thallium(l) acetate-iodine. Triphenylmethylphosphonium permanganate. 

Sulfuric acid promotes cyclization of (V./V-diphenylhydroxylamine (14) to carbazole (11) (13CB3306). The parallel conversions of diphenyl sulfoxide (15) and diphenyl selenoxide to dibenzothiophene (10) (23CB2275) and dibenzoselenophene (39CR(i99)53i) are effected by sodamide. 

Dibenzoselenophene has been obtained by the sodamide promoted cyclization of diphenyl selenoxide (153) (34CR(l99)53l), and via diazotization of o-aminodiphenyl selenide (154) (39JCS151). 

By elimination reactions of selenides or selenoxides Diphenyl diselenide, 125 Hydrogen peroxide, 145 Other elimination reactions Chloromethyldiphenylsilane, 74 m-Chloroperbenzoic acid, 76 Hydrogen peroxide, 145 Iodomethyltrimethylsilane, 315 Lithium 4,4 -di-/-butylbiphenylide, 162... 

Diphenyl selenium dichloride, (C6H5)aSeCl2, is formed when diphenyl selenoxide is treated with hydrochloric acid. It crystallises in glistening prisms, M.pt. 179° to 180° C.4 A similar product is obtained when diphenyl selenide is dissolved in an excess of concentrated nitric acid and concentrated hydrochloric acid added.5... 

Diphenyl selenoxide, (C6H5)2SeO.—This oxide may be prepared in several ways (1) Diphenyl selenium dichloride is treated with sodium hydroxide.6 (2) Diphenyl selenium dibromide is allowed to react with sodium hydroxide.7 (3) 7 grams of diphenyl selenide are slowly treated with 10 c.c. of 46 perhydrol. 8 (4) Diphenyl selenoxide... 

Phenyl methyl selenium dihydroxide, (C6H5)(CH3)Se(OH)2.— The dibromide (10 grams) is triturated with a suspension of 12 grams of silver oxide in 100 c.c. of water until the yellow colour disappears. Filtration, evaporation and desiccation yield about 8 c.c. of the hydroxide as a viscous oil. When heated at 100° C. at 15 mm., or at 170° C. at 760 mm., it decomposes, yielding phenyl methyl selenide, diphenyl diselenide and formaldehyde. The formation of formaldehyde is in agreement with the view that phenyl methyl selenoxide may exist in two isomeric forms, which, being unstable, decompose thus ... 

Treatment of the hydronitrates in aqueous solution with sodium carbonate causes evolution of carbon dioxide. Evaporation to dryness, followed by extraction with alcohol or benzene, then yields oils which are probably the selenoxides. These oils with concentrated hydrochloric acid are converted into white solids, crystallisable from benzene, xylene, alcohol or dry ether. These solids are the dichlorides of the original selenides, and when prepared by this method their melting-points are as follows Phenyl methyl selenium dichloride, M.pt. 122° C. phenyl ethyl selenium dichloride, M.pt. 64° to 65° C. diphenyl selenium dichloride, M.pt. 142° C. 

The readily available reagent diphenyl selenoxide has been used as a mild and selective oxidant in the synthesis of aporphines (and homoaporphines). When the benzylisoquinoline (13) was treated with one equivalent of the reagent at room temperature in methanol, and the product was O- methylated with diazomethane, the aporphine (14) was obtained in 80% yield. The alternative use of chloranil, which is a commonly used oxidant for catechols, yielded less than 10% of (14).20... 

Oxidation of A-diethylphosphito to A-diethylphosphono derivatives 151 has been performed using 2-picoline A-oxide, MCPBA, diphenyl selenoxide, or 7-butyl hydroperoxide (TBHP). The latter was selected as the most efficient reagent. Similarly, the N-phosphitylated /3-sultams undergo reactions of oxidative addition of elemental sulfur and selenium giving 2-thio- and 2-selenophosphono /3-sultams 152 and 153, respectively, in satisfactory yields (Scheme 46) <1999HAC61>. 

Tanaka H, Ishihara M, Ichino K, Ito K (1988) Synthesis of Natural Coumarinolignans Oxidative Coupling of 7,8-Dihydroxycoumarins and Phenylpropenes in the Presence of Diphenyl Selenoxide. Heterocycles 27 2651... 

QUINONES Benzeneseleninic anhydride. Diphenyl selenoxide. l-Methoxy-3-methyl-l-trimethylsilyloxy-1,3-butadiene. 

Oxidation of catechols. In accordance with earlier reports, diphenyl selenoxide selectively oxidizes o- and p-hydroquinones and has no efiect on simple phenols. An example is the oxidation of 3,5-di-f-butyIcatechol in methanol at 0° to the corresponding o-quinone, possibly via a selenurane (a) (equation I). 

The first example of a catalytic approach to the selenium promoted conversion was reported by Torii, who described an oxyselenenylation-deselenenylation process using catalytic amounts of diphenyl diselenide [115]. The electrophilic species was produced from the diselenide by electrochemical oxidation in the presence of the alkene 233 in methanol or in water. As indicated in Scheme 36, the addition product is electrochemically oxidized to afford the selenoxide which by elimination gives the allylic ether or alcohol 234 and the phenylselene-nic acid which continues the cycle by adding again to the alkene 233. 

Although the first alkynylselenonium salt, ethylmethylphenylethynyl sele-nonium picrate,was prepared as early as 1965 [10], it is only very recently that the first reactions of selenonium salts have been reported [11]. Among these salts, acyclic dimethyl(phenylethynyl)selenonium tetrafluoroborate (9) was prepared by methylation of methyl phenylethynyl selenide (10) with Meer-wein s reagent. The acyclic derivative 11 and the cyclic analogue 12 were synthesized by treatment of trimethyl(phenylethynyl)silane (13) and triflu-oromethanesulfonic anhydride with diphenyl selenoxide (14) and dibenzose-lenophene 5-oxide (15), respectively (Scheme 2). 

Simultaneously, 79 [36] and other selenoxides (dibenzyl [37], diphenyl [38] andbis(p-methoxyphenyl)selenoxide [39]) were applied as selective agents for the oxidation of various functional groups. 

Quinoxaline is alkylated with selenuranes, which are formed by the reaction of diphenyl selenoxide and carboxylic anhydrides, under irradiation. This reaction is presumed to proceed by a radical pathway accompanying decarboxylation. 

Likewise, diphenyl selenoxide has been shown to convert aromatic amines to the corresponding azobenzenes, while, in contrast to their sulfur analogs, benzeneseleninic acid and its anhydride are well established as versatile oxidants in organic chemistry. ... 

---