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Se-Phenyl areneselenosulfonates: their facile formation and striking chemistry

Gancarz, Roman A.; Kice, John L. (Dep. Chem., Texas Tech Univ., Lubbock, TX 79409, USA). J. Org. Chem., 46(24), 4899-906 (English) 1981. CODEN: JOCEAH. ISSN: 0022-3263. DOCUMENT TYPE: Journal CA Section: 25 (Noncondensed Aromatic Compounds) Section cross-reference(s): 22 Benzeneseleninic acid reacts rapidly at 0° with 2 mol arom. sulfinic acids to form Se-Ph areneselenosulfonates I (R = H, Me, Cl) in high yield. In contrast to thiosulfonates, PhSSO2C6H4R-4, areneselenosulfonates are extremely photosensitive and undergo quite rapid photodecompn. The principal products of this photodecompn. are the sulfonic anhydride II and PhSeSePh. In the presence of added alkenes the facile photodissocn. of I can be used to initiate a free-radical chain reaction that results in the addn. of I to the alkene to form b-phenylseleno sulfones in good yield. The b-phenylseleno sulfones can be converted to synthetically useful a,b-unsatd. sulfones by oxidn. of the b-phenylseleno group to the corresponding selenoxide and subsequent elimination of PhSeOH. Photoaddn. of I to 2,5-norbornadiene gives a 5-(phenylseleno)-exo-3-nortricyclyl aryl sulfone as the almost exclusive product, while photoaddn. to 1,5-cyclooctadiene gives a mixt. of approx. equal amts. of the 1,2-adduct, 5-(phenylseleno)-6-(arylsulfonyl)-1-cyclooctene, and the product of transannular addn., 6-(phenylseleno)-exo-2-(arylsulfonyl)-cis-bicyclo[3.3.0]octane. Besides their extraordinary ease of photodissocn., I also react extremely readily with nucleophiles: Nu- + PhSeSO2C6H4R-4 ? PhSeNu + 4-RC6H4SO2-. Kinetic studies show that the reactivity of PhSeSO2C6H4R-4 with cyanide ion in such a reaction is 70000 times larger than the reactivity of the corresponding thiosulfonates, PhSSO2C6H4R-4.

Selenium compounds as reagents and catalysts for oxidation of organic compounds

Selenium compounds as reagents and catalysts for oxidation of organic compounds. Mlochowski, Jacek; Brzaszcz, Monika; Giurg, Miroslaw; Wojtowicz, Halina (Inst. Chem. Org., Biochem. i Biotechnol., Politechnika Wroclawska, Wroclaw 59-370, Pol.). Wiadomosci Chemiczne, 55(1-2), 9-44 (Polish) 2001 Wydawnictwo Uniwersytetu Wroclawskiego. CODEN: WICHAP. ISSN: 0043-5104. DOCUMENT TYPE: Journal; General Review CA Section: 21 (General Organic Chemistry) Review on applications of selenium and its compds. in oxidn. reactions. One of such compds. is selenium(IV) oxide, easily available reagent for hydroxylation of activated a-positions particularly at allylic and propargylic sites. It also can introduce carbonyl functionality at activated positions. Used in combination with hydrogen peroxide or tert-butylhydroperoxide it acts as oxygen-transfer agent. Both of these hydroperoxides can be used in the presence of selenium(IV) oxide for epoxidn., 1,2-dihydroxylation and a-carbonylation of alkenes, for oxidn. of aldehydes into carboxylic acids, sulfides to sulfoxides or sulfones, secondary amines to nitrones and for other reactions. Benzeneseleninic acid, other areneseleninic acids and their anhydrides are known as stoichiometric oxidants or activators of other oxygen donors. They have been successfully applied for oxidn. of many org. compds., among them alkenes, alcs., phenols, amines, hydrazones, sulfides, 1,3-dithiolanes and azines. Org. diselenides, the precursors of seleninic acids, have been used as oxygen-transfer catalysts for oxidn. of various functional groups with hydrogen peroxide, t-butylhydroperoxide and other oxygen donors while di-Me and di-Ph selenoxides are efficient stoichiometric oxidants (e.g. for conversion of halomethyl or hydroxymethyl group into formyl group). Most recently, selenenamides, particularly 2-phenyl-1,2-benzisoselenazol-3(2H)-one (ebselen) and its analogs were found as efficient catalysts for hydrogen peroxide and t-butylhydroperoxide oxo functionalization of olefins, oxidn. of azomethine compds. and sulfides.