Diphenylseleninic anhydride

In the presence of HMDS 2 phenol reacts with diphenylseleninic anhydride 1354 to give, via 1355, 1356, which is further oxidized via 1357 to give the N-phe-nylselenoquinonimine 1358 in 45% yield [102] (Scheme 8.40). 

Interestingly the allenic thioacetal (123) was obtained from the a-hy-droxythioacetal (122). ° The diphenylseleninic anhydride oxidation of 3/3-t-butyltellurocarbonyloxy-5a-cholestane (124) provided the ester (125) whereas reduction with NaHTe gave the ether (126) and the dimeric ether (127). ° ... 

Aromatic Substitution - Phenols can be oxidized directly to ortho-quinones with diphenylseleninic anhydride.1,6 Blocking of the para-posit ion is unnecessary and yields are good. 

Diphenyl-l-propanol, 649 Diphenyl selenide, 240 Diphenylseleninic anhydride, 240-241 Diphenyl sulfide, 241... 

There are two new methods for dethioacetalization—photosensitized autoxida-tion and, specifically for dithiolanes, oxidation using Ph2Sc203 (diphenylseleninic anhydride). ... 

The reaction of phenols with diphenylseleninic anhydride and hexamethyldisilazane gives the corresponding phenylseleno-imines (eq The products thus obtained can be converted to the aminophenol or reductively acetylated using zinc and acetic anhydride The use of ammonia or tris(trimethylsilyl)amine in place of HMDS gives only trace amounts of the selenoimines. 

Oxidation.—Diphenylseleninic anhydride and benzeneseleninyl chloride have both been used to oxidize primary amines to carbonyl compounds (Scheme 8). 

To obtain hop alpha acids, oxidation of 14 has to be carried out at the aromatic carbon atoms carrying the alkenyl side chains. A number of oxidation methods are available, for example reaction with antimony pentachloride at -50°C and hydrolysis in the presence of siiver(l) ions (85) oxidation with iead(IV) acetate in acetic acid (83) or with trifiuoroacetic acid and hydrogen peroxide (87) base-cataiyzed reaction with benzoyl peroxide (88) oxidation with diphenylseleninic anhydride in dichloromethane (89). These reagents and reaction conditions however are deleterious to the very unstable 4-deoxy-alpha acids. Oxidation with air oxygen in controlled conditions is therefore appropriate. 

Diphenylseleninic anhydride, (PhSeO)20, has been used for the oxidation of phenols. The relatively new phenylselenimine (54) has been formed from (53) in the presence of hexamethyldisilazane, while the phenolate ion derived from 2,6-xylenol (55) resulted in the o-hydroxydienone dimer (56). 

Phenols react with hexamethyldisilazane in the presence of diphenylseleninic anhydride, forming phenylseleno-imines, with a strong preference for ortho reaction. The resulting imines are easily reduced to amino-phenols. ... 

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