A-Phenyl selenide

From halides. Halides are easily converted into selenides. Since halides are also suitable radical precursors, this transformation is usually done when side reactions of halides with nucleophiles can occur. An example of this type is reported in Eq. (1). The bromide 5 was converted into a phenyl selenide, which could stand DIBALH reduction and imine formation. Tin mediated cyclization of 6 afforded the cyclopentylamine 7 in 72% yield [5]. 

Reaction between the palladium pincer complex 115 and trimethylstannylphenylselenide 116 is assumed to result in formation of a phenyl selenide-coordinated complex 117 (Equation 24) <2005JOC9215>. 

It has been produced most frequently from a f-butyl ketone (45), although a phenyl selenide (46) was also employed in some investigations. 

The 7 a-bromo steroid (9) can also be treated with sodium phenyl selenolate (41). The resultant 7 P-phenyl selenide (13) can be oxidized and the corresponding phenyl selenoxide elirninated to form the 7-dehydtocholesteryl ester (11). 

Diseleno acetals and ketals are cleaved more rapidly than their dithio counterparts a methyl derivative is cleaved more rapidly than a phenyl derivative. Methyl iodide or ozone converts diseleno acetals and ketals to vinyl selenides. ... 

Trifluoromethyl thiirane is formed by the action of tris(diethylamino)-phosphineon l-chloromethyl-2,2,2-trifluoroethyldisulfide [S2] (equation 73) Difluoromethyl phenyl selenide is prepared by treatment of lithium phenyl-selemde with chlorodifluoroniethane via a carbene mechanism [Si] (equation 44) Bis(2,2,2-trifluoroethyl)diselenide is formed in the reaction of 2,2,2-trifluoroethyl mesylate with lithium diselenide [84] (equation 74). 

The number of reported reactions in which the radical derived from the decomposition of AIBN plays a role in the termination process has increased considerably. Often these reactions are not radical chain reactions, since the initiator is used in stoichiometric amounts. A few examples of rearomatization of cyclohexadienyl radicals by disproportionation have been reported herein. Below are some other examples, where the phenyl selenide 61 reacts with (TMSfsSiH (3 equiv), AIBN (1.2 equiv) in refluxing benzene for 24 h to give the coupling product of radicals 63 and 64 in good yields (Scheme 9).i24,i25 these cases,... 

A variety of compounds have been examined which are in the phosphinic acid class. They include a phenyl cyclopentyl ester,184 a phosphinothioic anhydride,185 a dipheny1phosphinamide, 86 a red bis(di-t-buty1thiophosphinamide) and its selenide analogue,187 the anisylphosphor inane (67),1 88 the thioamide (68),1 89 and the phospholenium amide (69, Y = i-Pr2N).190... 

In a range of anions PhZ (Z = O, S, Se, Te), for example, the thiophenolate ion (PhS ) effectively traps aryl radicals (Ar ), whereas the anion of phenyl selenide (PhSe ) is 20 times less active, and the phenolate anion (PhO ) is absolutely inactive. The reaction of aryl radicals with phenyl-telluride ions (PhTe ) proceeds in an abnormal fashion—both asymmetrical and symmetrical tellurides are produced (Rossi and Pierini 1980). 

T(—H) can also be formed in a two-step process involving radical cation formation produced by photosensitizers operating through a type I mechanism, followed by deprotonation. Cadet has also developed the photolabile phenyl sulfide precursor that upon irradiation at 254nm generates T(—H). " The corresponding phenyl selenide" and methoxy-substituted sulfides" were developed by the Greenberg... 

Transfer of a metal carbene moiety from a metal carbene complex to a heteroatom other than oxygen, sulfur, and nitrogen is possible. One such example is the report by Uemura and co-workers, who disclosed catalytic asymmetric reaction of ethyl diazoacetate with ( )-cinnamyl phenyl selenide 193 (Equation (30))." The reaction afforded 194 as a diastereomeric mixture (58 42). Using Rh2(5[Pg.173]

Formation of CK-configurated cyclobutanones has also been observed with 2-methylcyclopen-tanone and 2-methylcyclohexanone/8 However, stereoreversed eyclobutanone formation can be achieved by opening the intermediate oxaspiropentane with sodium phenyl selenide, oxidation of the resulting / -hydroxy selenide with 3-chloroperoxybenzoic acid and subsequent rearrangement in the presence of pyridine/18 Thus, from one oxaspiropentane 8, either stereoisomeric eyclobutanone cis- or lrans-9 was produced. The stereoreversed eyclobutanone formation proceeds from a stereohomogenous / -hydroxy selenoxide and is thought to be conformationally controlled. 

Utilizing selenoxide syn elimination as the key step, a two-step procedure has been developed for the conversion of ketones to enones.22 Cyclobutyl phenyl ketone (52) and 3-phenylcyclobu-tanone (55) were both transformed via the phenyl selenides to the corresponding 1-cyclobutenyl phenyl ketone and 3-phenyIcyclobut-2-en-l-one in 74 and 26% overall yield, respectively.22... 

OH - Br. A primary or secondary alcohol can be converted to the alkyl phenyl selenide by reaction with phenyl selenocyanate and tri-n-butylphosphine (7, 252-253). Reaction with Br2 and triethylamine (7, 34-35) replaces the SeC6H5 group by Br. 

Phenyl selenides.2 In the presence of a ruthenium catalyst, prepared by reaction of RuCly with 3 equivalents of potassium, lithium benzencselenolate reacts with a wide variety of tertiary amines to form phenyl selenides in excellent yield. Anhydrous diglyme is used as solvent. 

Atkenes from sic-dihaiides. The reaction of /c-dihalides with NaSeCH3 or NaSeC6H5 in ethanol or THF-HMPT (3 1) results in alkenes. The reaction involves a formal a rr-elimination in the case of wc-dibromides or uie-chloroiodidcs, but a formal xyn-elimination in the case of w c-dichlorides. Elimination to form alkenes also occurs with /K-haloalkyl phenyl selenides. 

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. 

The only example of the generation of a monocyclic heterocycle by y-bond formation is provided by the thermally promoted conversion of the bisallenyl selenide (143) into the selenophene (144) (78TL1493). The cyclization is conveniently formulated as proceeding via an intramolecular ene reaction. Another electrocyclic process appears to be involved in the conversion of allyl phenyl selenide (145) into 2-methyl-2,3-dihydrobenzo[6]seleno-phene (146) (71TL49). The origin of the minor amount of 2-methylbenzoselenophene (147) which is also formed has not been established. Access to 3-keto-2,3-dihy-drobenzo[h]selenophenes (148) (71KGS333) and 2-arylidene-3-keto-2,3-... 

Another example of oligomer preparation by C-C bond formation is outlined in Figure 16.30. In this synthesis, nitroalkyl phenyl selenides are converted into nitrile oxides in the presence of support-bound terminal alkenes, forming isoxazolines. Oxidative elimination of the selenide yields a new alkene, which can then be subjected to further 1,3-dipolar cycloaddition with a new nitrile oxide. Although this synthesis is short and easy to perform, the cycloadditions proceed with low diastereoselectivity... 

Alkenes from organomercurials.1 Photoinitiated reaction of diphenyl diselenide with the organomercurial 1 provides a mixture of the corresponding a- and P-phenyl selenides, which undergo oxidative elimination to 2. The reaction provides a key step in a total synthesis of K-76 (3), which counteracts the inflammatory... 

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