Benzeneselenenic acid

A 30% solution of hydrogen peroxide in water was purchased from Mallinckrodt Chemical Works. The reaction requires 2 molar equivalents of hydrogen peroxide, the first to oxidize the selenide to the selenoxide and the second to oxidize the elimination product, benzeneselenenic acid, to benzeneseleninic acid. The submitters recommend that the hydrogen peroxide solution be taken from a recently opened bottle, or titrated to verify its concentration. 

Alkyl phenyl selenones undergo substitution reactions with a number of nucleophiles with concomitant formation of benzeneselenenic acid. 

Aromatization of cyclohexenonesf This reaction is possible by selenenylation of (lie lithium enolate of the cyclohexenone, followed by oxidation of the resulting xclcnide. To obtain satisfactory yields of the phenol, an aromatic amine is added in llu oxidation step to react selectively with the benzeneselenenic acid formed. For this pin pose, 3,5-dimethoxyaniline is the most satisfactory amine. 

Oxyselenation ofalkeues, - Treatment of olefins with 1 or 2, water, and an acid catalyst (e.g., p-TsOH) in CH2CI2 affords j3-hydroxy selenides in excellent yield. Unsaturated carboxylic acids, phenols, alcohols, thioacetates, and urethanes react with 1 or 2 and an acid catalyst ( —78- 25°) to afford products of oxidative cyclization. These reagents are superior to benzeneselenenyl halides for selenium-induced ring closures. This reaction is also useful for synthesis of 14- and 16-membered lactones. Benzeneselenenyl halides and benzeneselenenic acid do not promote macrolide formation under similar conditions. 

Disubstituted alkenes. Under controlled conditions to prevent a-deprotonation or C—Se cleavage (DME or ether, 0°) alkyllithium reagents (with the exception of methyllithium) add to phenyl vinyl selenide to give a-lithioalkyl phenyl selenides (2), which can be trapped with electrophiles to give 3. On oxidation, these products form alkenes (4) by elimination of benzeneselenenic acid. The reagent thus functions as CH=CH. 

Baeyer-Villiger oxidation, 56, 196, 324, 509 Barium manganate, 23 Barium oxide, 23 Beckmann rearrangement, 472 Benzal chlorides, 465 Benzeneboionic acid, 23-24 7) -Benzenechiomium tricarbonyl, 117 Benzeneselenenic acid, 24 Benzeneselenenic anhydride, 2S Benzeneselenenyl bromide, 25-32 Benzeneselenenyl chloride, 25-32 Benzeneseleninic acid, 32 Benzeneseleninic anhydride, 32-34 Benzeneselenocyanate-Copper(II) chloride, 34-35... 

P-Hydroxy selenides are conveniently prepared from epoxides by treatment with sodium phenylse-lenide (Scheme 32) and by the addition of benzeneselenenic acid and its derivatives to alkenes (Scheme 33), - -" although in some cases these reactions are not regioselective. Useful phenylseleno -etherification and -lactonization reactions have been developed which can be regioselective (equation 42 and Schemes 34 and 35). -" " Selenide- and selenoxide-stabilized carbanions have been used in addition reactions with aldehydes and ketones, - and the reduction of a-seleno ketones also provides a route to P-hydroxy selenides. ... 

A similar removal of benzeneselenenic acid from l,l-dichloro-la-phenylseleninyl-la,9b-di-hydro-l//-cyclopropa[/]phenanthrene (2) at ambient temperature was used to generate 1,1-dichloro-l//-cyclopropa[/]phenanthrene as a short-lived intermediate which was trapped by addition of methanol.Elimination of the elements of HSe Mcj from 3, derived from la-methylselenacyclopropa[/]phenanthrene and la,9b-dihydro-l//-cyclopropa[/]phenanthrene after alkylation, gave a mixture of the alternative cyclopropene, which were both trapped with furan. 

The initial oxidation of the hydrazide 48 is expected to generate the corresponding acyl- or aroyldiazene 50 and benzeneselenenic acid. Further reaction of these species produces the hypothetical intermediate 51, followed by nitrogen extrusion leading to selenol ester formation (Scheme 13). 

Benzeneselenenic acid, CeHaSeOH. Mol. wt. 173.07. The reagent is generated in situ from benzeneseleninic acid and diphenyl diselcnide ... 

Benzeneselenenic acid can be prepared and used in the same way as methane-selenenic acid it reacts somewhat more readily. 

The thermolysis of 2,2-dimethyl-2,3-dihydrobenzo[6]selenophen oxide (215) proceeded by sy/i-elimination of selenoxide and intramolecular addition of the intermediate benzeneselenenic acid, Cleavage of 5-triselenan by its reaction with bromine offers a preparative pathway to bis-(bromomethyl) selenide. A series of naphthalene and tetracene dichalcogenides (216 X, Y = S, Se, or Te) were... 

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