Selenides reactions with alkenes

Oxyselenation. In the presence of hydrogen peroxide the selenide reacts with alkenes to form acctoxyselenated products yith loss of formaldehyde. The reaction apparently involves formation of the selenoxide, and indeed no reaction occurs in the absence of H2O2. Presumably the selenoxide then loses formaldehyde to form methaneselenenyl acetate, CHaSeOAc, which is the actual reagent. Examples ... 

Synthesis of alkenes. Terminal alkenes are formed in good yield by oxidation of primary alkyl 2-pyridyl selenides with a slight excess of H202 (equation I). The same reaction with primary alkyl phenyl selenides proceeds in much lower yield. 

Reactions of phosphines and phosphites have received some attention but their preparative value is limited. The zwitterion formed from diphenylmethylphosphine and benzyne rearranges to ylide (124) which can be captured by Wittig alkenation, with cyclohexanone, in about 20% yield.159 Some synthetically useful reactions of tellurium and selenium compounds with arynes have been reported. For example, heating diphenyl iodonium carboxylate and bis(p-ethoxyphenyl) ditelluride in dichlorobenzene affords the compound (125).160 The corresponding reactions with diphenyl selenide and diphenyl sulfide... 

Treatment of a,a-dicyanoalkyl phenyl selenide (14) with vinyl ether initiated by AIBN under benzene refluxing conditions generates methyl ketone (15) (eq. 4.8). An electrophilic a,a-dicyanoalkyl radical is first formed, and then it adds to vinyl ether, followed by hydrolysis. Diethyl 3-iodoalkylphosphonate (17) can be formed through AIBN-initiated addition reaction of diethyl 1-iodomethylphosphonate (16) to alkene (eq. 4.9). This is an atom-transfer reaction. Both reactions (eqs. 4.8 and 4.9) do not require Bu3SnH. 

Maradyn, D.J. and Weedon, A.C. (1994) The photochemical cycloaddition reaction of2-cydohexenone with alkenes trapping of triplet 1,4-biradical intermediates with hydrogen selenide. Tetrahedron Letters, 35, 8107-8110. 

The stereoselective formation of /3-hydroxy selenides has also been reported 36 in the reaction of alkenes with, V-(phenylseleno)phthalimide or the succinimide derivative in aqueous acetonitrile or dichloromethane. The use of phenylselenenyl chloride under these conditions gives similar results (Table 5)37. 

Table 9. /3-Acylaminoalkyl or /5-Acylaminocycloalkyl Phenyl Selenides by Reaction of Alkenes with Phenylselencnyl Chloride, Nitriles, Trifluoromethanesulfonic Acid, and Water64...

The reaction of phenylselenenyl chloride with alkenes in acetonitrile containing trifluorometha-nesulfonic acid and a small amount of water afforded /J-acetylamino selenides 10 in good to excellent yield34 3S. 

Further reaction of Aese species with carbonyl compounds and hydrolysis of the resulting alkoxide leads to p-oxidoalkyl selenoxides which have been transformed into allyl alcohols on thermal decomposition (Schemes 51, 52 and 54, entry a see Section 2.6.4.4) or reduced to p-hydroxyalkyl selenides or to alkenes (Scheme 53). P-Oxidoalkyl selenoxides derived from cyclobutanones react in a different way since Aey rearrange to cyclopentanones upon heating (Scheme 54, b. Schemes 120 and 121 and Section 2.6.4.5.3). 

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. ... 

Trimethylsilyl-l-alkenes. The lithium reagent is prepared from the corresponding selenide by treatment with BuLi. Its reaction with alkyl halides provides the allylsilanes. 

Atomic selenium was monitored in flashed CSe2 by kinetic absorption spectroscopy, and its rate of reaction with ethylene was measured in the temperature range 302-412 K. The rate of appearance of a new spectrum in the far ultraviolet (intense bands at 2259 and 2208 A) was symmetrical with atomic decay, and was assigned to ethylene selenide, i.e. selenirane (1) (Equations (la) and (lb)). Absorption spectra of flashed CSe2 and alkene mixtures show band systems in the 2000-2300 A region which do not occur in flashed saturated-hydrocarbon and CSe2 mixtures. The band centers obtained from their spectra are listed in Table 4. 

Balczewski, P., Pietrzykowski, W.M., and Mikolajczyk, M., Studies on the free radical carbon-carbon bond formation in the reaction of a-phosphoryl sulfides and selenides with alkenes. Tetrahedron, 51, 7727, 1995. 

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