An indium-TMSCl promoted reaction of diphenyl diselenides and aldehydes: novel routes to selenoacetals and alkyl phenyl selenides

The reaction of diphenyl diselenides with aldehydes in the presence of In-TMSCl has been investigated. Aliphatic aldehydes provide the corresponding selenoacetals, whereas aromatic aldehydes lead predominantly to alkyl phenyl selenides under the same reaction conditions. This constitutes a new approach for the synthesis of selenoacetals and selenides from aldehydes.     

Metallation of benzyl selenides and of α-aryl selenoacetals. Scope and limitations.

α-Metallo benzylselenides and α-metallo selenoacetals derived from aromatic aldehydes have been conveniently prepared by metallation of the corresponding carbon acids. KDA in THF proved among the various basic systems tested, the most efficient.α-Metallo benzylselenides and α-metallo selenoacetals derived from aromatic aldehydes have been conveniently prepared by metallation with KDA of the corresponding carbon acids. These reactions have been used for the synthesis of arylalkanes, including those bearing a trialkylated benzylic carbon, from aromatic aldehydes.     

α-Phenylselenenylation of aldehydes and ketones with diphenyl diselenide mediated by KF/Al2O3

The utility of KF/Al₂O₃ for the synthesis of α-phenylseleno aldehydes and ketones from the corresponding aldehydes or ketones and diphenyl diselenide has been investigated. Simple stirring of a mixture of aldehyde or ketone and diphenyl diselenide in the presence of KF/Al₂O₃ at room temperature selectively produces the corresponding α-phenylseleno aldehyde or ketone in good to excellent yields.     

A convenient method for the synthesis of α-phenylselenenyl carbonyl compounds

Treatment of ketones or aldehydes with selenium dioxide and diphenyl diselenide in the presence of acid catalyst afforded the corresponding α-phenylselenenyl carbonyl compounds in good yields.     

Synthesis and anti-hiv-1 activities of 6-arylthio and 6-arylselenoacyclonucleosides

6-Arylthio and 6-arylselenoacyclonucleosides was synthesized and tested for the ability to inhibit replication of HIV-1. Lithiation of acyclonucleosides with LDA followed by reaction with the electrophiles phenyl disulfide, diphenyl diselenide, 2,2′-dipyrdyl disulfide or 2,2′-dipyridyl diselenide afforded 6-(arylthio or arylseleno)acyclonucleosides 5a-c, 6, 7, 9, 15a-c, 17a-c . Compounds 19a-c and 20a-c were obtained by deprotection of corresponding TBDMS derivatives. Dehydrated products 16a , and 18a-c were also formed during the reactions. 5-Ethyl-6-(α-pyridylthio or α-pyridylseleno) disubstituted acyclouracils 6 and 7 were more active against HIV-1 in both MT-2 and CEM-IW cell lines than AZT, DDC, DDI or D4T. The EC₅₀ of 6 against HIV-1 in CEM-IW cell was in the nanomolar range with a therapeutic index of 1100.     

Highly selective anti-markownikoff type oxidation of olefinic bonds of allylic alcohol derivatives. Specific synthesis of β-alkoxy α-phenylseleno carbonyl compounds

On treatment with diphenyl diselenide and benzeneseleninic anhydride, 3-$\text{t}$-butyldimethylsiloxy-1-alkenes were converted to the corresponding α-phenylseleno aldehydes exclusively.     

二苯基二乙基季镂盐及二苯基二苄基季镂盐与取代芳醛的相转移催化Wittig反应

众所周知,三苯基型稳定季鏻盐的 Wittig反应具有 Z-式选择性,其 PTC-Wittig 反应亦具有 Z-式选择性,三苯基型半稳定季鏻盐的 Wittig 反应的立体选择性较差,其产物的Z/E 约为1∶1～1∶1.5。我们曾报道二苯基烯丙基型半稳定季鏻盐与芳醛的 PTC-Wit-     

Photochemical substitution of olefins and aromatic compounds with difluoromethyl radicals bearing ester and phosphonate groups

Efficient and selective substitution of cyclic and acyclic vinyl ethers with photo-generated difluoromethyl radicals bearing ester and phosphonate groups, in the presence of 2,4,6-trimethylpyridine and diphenyl diselenide was successfully carried out to provide the corresponding regioselective unsaturated difluoromethylene adducts selectively. The reaction involves phenylselenyl transfer at an early stage followed by elimination of phenylselenol from the adducts once formed to provide the unsaturated difluoromethylene adducts selectively. This novel photochemical method was successfully extended to aromatic and heteroaromatic substitutions to provide the corresponding α-aryl-α,α-difluoroacetates and α-aryl-α,α-difluoromethylphosphonates in good to moderate yields.     

Iodosobenzene Diacetate and Diphenyl Diselenide: An Electrophilic Selenenylating Agent of Double Bonds

Phenylseleno-acetoxylation, hydroxylation, etherification and lactonization products are obtained in good yields from the reaction of alkenes with diphenyl diselenide and iodosobenzene diacetate, in acetonitrile.

     

Comparative Behavior of Aromatic Disulfide and Diselenide Monolayers on Polycrystalline Gold Films Using Cyclic Voltammetry, STM, and Quartz Crystal Microbalance

A comparative investigation of the self-assembled monolayers of diphenyl disulfide (DDS), diphenyl diselenide (DDSe), and naphthalene disulfide (NDS) on polycrystalline gold films using STM, QCM, and electrochemical techniques is presented. The geometric constraint imposed by the rigid naphthalene ring for NDS inhibits the cleavage of the S-S bond, thus adversely affecting the monolayer organization and stability relative to the monolayers formed with DDS and DDSe. A comparative analysis using techniques like cyclic voltammetry and quartz-crystal microbalance indicates that, for DDS, the facile cleavage of the S-S bond leads to strong binding of the adsorbate molecules at the preferred surface sites, resulting in a rather well-organized self-assembled structure. The STM pattern of NDS reveals a periodic domain (i.e., less than 10 nm in size) while no such small domains are seen in the case of DDS and DDSe due to the orientational flexibility of the rings. Copyright 2001 Academic Press.     

Electrophilic Reaction of Phenyl Bis(Phenylthio) Sulfonium Cation as an Active Species for the Oxidative Polymerization of Diphenyl Disulfide

Computer modeling predicts that the methyl bis(methylthio) sulfonium cation can act as an efficient electrophile for sulfide bond formation in which the sulfur atoms at the side position of the cation react with the phenyl ring of an aromatic molecule. The electrophilic reaction mechanism of phenyl bis-(phenylthio) sulfonium cation with anisole was examined using computer simulation. The reaction between phenyl bis- (phenylthio) sulfonium cation, which is a homogeneous structure of thecation, and anisole shows the efficient formation of 4-phenylthioanisole with diphenyl disulfide as a by-product. In the oxidative polymerization of diphenyl disulfide, the formation process of polyp-phenylene sulfide) includes an elementary reaction between the phenylthio group at each side position of the phenyl bis(phenylthio) sulfonium cation and the carbon at the para position of the phenyl ring.     

Ionic liquid/PPh3 promoted cleavage of diphenyl disulfide and diselenide: a straight-forward metal-free one-pot route to the synthesis of unsymmetrical sulfides and selenides

A metal-free cleavage of diphenyl disulfide and diphenyl diselenide has been achieved using ionic liquid/triphenyl phosphine (PPh₃) and a convenient protocol for the one-pot synthesis of unsymmetrical sulfides and selenides by condensing ‘in situ’ generated thiolate or selenate anion with alkyl halides has been developed. In addition, 1,4-conjugate addition of the generated thiolate anions to activated alkenes has also been demonstrated. The ionic liquid, 1-methyl-3-pentyl imidazolium bromide, [pmIm]Br plays a crucial role in promoting the course of the reactions and shows superior activity and selectivity compared to other solvents. The [pmIm]Br has been reused for at least five times without appreciable loss of activity.     

Reduction of diphenyl diselenide and analogs by mammalian thioredoxin reductase is independent of their gluthathione peroxidase-like activity: a possible novel pathway for their antioxidant activity

Since the successful use of the organoselenium drug ebselen in clinical trials for the treatment of neuropathological conditions associated with oxidative stress, there have been concerted efforts geared towards understanding the precise mechanism of action of ebselen and other organoselenium compounds, especially the diorganyl diselenides such as diphenyl diselenide, and its analogs. Although the mechanism of action of ebselen and other organoselenium compounds has been shown to be related to their ability to generally mimic native glutathione peroxidase (GPx), only ebselen however has been shown to serve as a substrate for the mammalian thioredoxin reductase (TrxR), demonstrating another component of its pharmacological mechanisms. In fact, there is a dearth of information on the ability of other organoselenium compounds, especially diphenyl diselenide and its analogs, to serve as substrates for the mammalian enzyme thioredoxin reductase. Interestingly, diphenyl diselenide shares several antioxidant and neuroprotective properties with ebselen. Hence in the present study, we tested the hypothesis that diphenyl diselenide and some of its analogs (4,4'-bistrifluoromethyldiphenyl diselenide, 4,4'-bismethoxy-diphenyl diselenide, 4.4'-biscarboxydiphenyl diselenide, 4,4'-bischlorodiphenyl diselenide, 2,4,6,2',4',6'-hexamethyldiphenyl diselenide) could also be substrates for rat hepatic TrxR. Here we show for the first time that diselenides are good substrates for mammalian TrxR, but not necessarily good mimetics of GPx, and vice versa. For instance, bis-methoxydiphenyl diselenide had no GPx activity, whereas it was a good substrate for reduction by TrxR. Our experimental observations indicate a possible dissociation between the two pathways for peroxide degradation (either via substrate for TrxR or as a mimic of GPx). Consequently, the antioxidant activity of diphenyl diselenide and analogs can be attributed to their capacity to be substrates for mammalian TrxR and we therefore conclude that subtle changes in the aryl moiety of diselenides can be used as tool for dissociation of GPx or TrxR pathways as mechanism triggering their antioxidant activities.     

Semisynthetic tellurosubtilisin with glutathione peroxidase activity

Reaction of the hydroxyl group of serine-221 of subtilisin with phenylmethanesulfonylfluoride followed by nucleophilic substitution with sodium hydrogen telluride, a semisynthetic telluroprotein, tellurosubtilisin, was prepared. Tellurosubtilisin, which displays high substrate specificity for aromatic thiols, exhibits remarkable peroxidase activity and catalyzes the reduction of hydrogen peroxide by 3-carboxy-4-nitrobenzenethiol 20 000 times more efficiently than diphenyl diselenide.     

Highly enantioselective addition of dimethylzinc to arylaldehydes catalyzed by (2S)-1-ferrocenyl-methylaziridin-2-yl(diphenyl)methanol

Asymmetric addition of dimethylzinc to a wide variety of aromatic aldehydes is described in the presence of a catalytic amount of chiral β-amino alcohol [(2S)-1-ferrocenyl- methylaziridin-2-yl(diphenyl)methanol], and a reaction enantioselectivity of up to 97.5% ee was achieved in this transformation in the absence of additional metals such as Ti or Ni. The results showed that this particular addition reaction, characterized by the lower reactivity of dimethylzinc with aldehydes, was more sensitive to structural variations in substrate aldehydes than the corresponding diethylzinc addition. A possible transition state for the catalytic asymmetric addition has been proposed on the basis of previous studies.     

Photochemical generation of difluoromethyl radicals having various functional groups and their highly regioselective addition to olefins and aromatic substitution

Difluoromethyl radicals bearing ester, phosphonate, nitrile, cyclic carbonate, and carbamate groups were generated by the photoinitiated S-CF₂ bond cleavage of electrosynthesized α,α-difluorosulfides, and their addition to olefins and aromatic substitution were successfully carried out to provide the regioselective adducts and substitution products in moderate yields. The yields of substitution products increased by the addition of diphenyl diselenide and 2,4,6-trimethylpyridine.     

Biscarbamoyl diselenides as new carbamoylating reagents. Lewis acid promoted carbamoylation of aromatic compounds

The reaction of biscarbamoyl diselenides with aromatic compounds in the presence of Lewis acids resulted in Friedel-Crafts type carbamoylation (Gatterman amide synthesis) to give corresponding aromatic amides in good yields. This methodology was successfully applied to aroylation and benzylation by use of dibenzoyl diselenide and dibenzyl diselenide, respectively.     

Carbon-13 NMR studies of diphenyl dichalcogenides, (C6H5)2X2 (X = S,Se, Te)

The ¹³C NMR chemical shifts and spin-lattice relaxation times for diphenyl disulfide, diselenide and ditelluride have been measured and assigned. The shielding effects experienced by the carbon atoms re qualitatively discussed in terms of the inductive and mesomeeric properties of the dichalcogen group. The attempt to calculate the magnetic shielding tensors for the ¹³C nuclei in terms of the Pople theory gave unsatisfactory results.     

Electrochemical cyclization of unsaturated hydroxy compounds. Part I. Phenylselenoetherification

One-step cyclization of alkenols has been accomplished by electrooxidative phenylselenoetherification. The reaction was performed by electrolysis of unsaturated alcohols and diphenyl diselenide in methylene chloride containing tetraethylammonium bromide.     

New chiral thio- and seleno-substituted ferrocenylamines

A new class of chiral thio- and seleno-substituted ferrocenylarnines were prepared by the dilithiation of R-(+)-N,N-dimethyl-1-ferrocenylethylamine followed by the reaction with either a disulfide or diselenide.