Using chiral nonracemic electrophilic-organoselenium-reagents-asymmetric alkoxy-, hydroxy-, azido- and amido-selenenylation of alkenes were effected with high diastereoselectivity. These reagents ...have also been employed in catalytic amounts to promote one-pot selenenylation-deselenenylation processes. The asymmetric cyclization of properly substituted alkenes diastereoselectively afforded lactons, tetrahydrofurans oxazolines, thiazolines, pyrrolidines, isoxazolidines, 1,2-oxazines, and cyclic nitrones. Enantiopure dioxane, morpholine, tetrahydrofuran, oxazolidin-2-one and aziridine derivatives were prepared from alkenes, PhSeX, and optically active nucleophiles or substrates.
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Chiral, nonracemic azidoselenides such as 2 are useful intermediates for the synthesis of enantiomerically enriched nitrogen‐containing compounds (e.g. 3). The asymmetric electrophilic ...azidoselenenylation of a variety of alkenes with the sulfur‐containing chiral selenenyl triflate 1 and sodium azide occurred with high facial selectivity to provide an array of azidoselenides, which were further elaborated.
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The first example of a kinetic resolution process promoted by an electrophilic selenium reagent is reported. Racemic allylic alcohols react with half equivalents of a selenenylating agent in methanol ...leading to the regiospecific formation of the corresponding addition products with a very high level of facial selectivity (98% de). The unreacted alcohol can be recovered in a optically enriched form (92% ee).
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The synthesis of the new chiral non‐racemic sulfur‐containing diselenide, di‐2‐methoxy‐6‐(1 S)‐1‐(methylthio)ethylphenyl diselenide, is described. When treated with ammonium persulfate this ...diselenide is transformed into the corresponding selenenyl sulfate, which acts as a strong electrophilic reagent and adds to alkenes, in the presence of methanol or water, to afford the products of selenomethoxylation or selenohydroxylation, respectively, with excellent diastereoselectivities. Starting from alkenes containing internal nucleophiles, asymmetric cyclofunctionalization reactions also resulted in good chemical yields, complete regioselectivities, and high diastereoselectivities. This sulfur‐containing diselenide can also be used in catalytic amounts to promote one‐pot selenenylation–deselenenylation processes, from which several types of products can be obtained in high yield and with good enantiomeric excess.
Excellent diastereoselectivities have been achieved with the new sulfur‐containing optically active diselenide 1 in both enantioselective addition reactions to alkenes (see scheme) and ring‐closure reactions. The efficient transfer of chirality is attributed to a strong interaction between the selenium and sulfur atoms. The diselenide 1 can also be used in catalytic amounts to promote one‐pot selenenylation–deselenenylation processes, from which several types of products can be obtained in high yield and with good enantioselectivity.
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A new and convenient method for the stereospecific synthesis of variously substituted 1,3‐oxazolidin‐2‐ones from the easily available β‐hydroxyalkyl phenyl selenides is presented. After ...transformation into the N‐tosyl or N‐benzoyl carbamates, the selenides were oxidized to the corresponding selenones. The key step of the process is the ring‐closure reaction, which occurs by stereospecific intramolecular nucleophilic substitution of the selenone group by the nitrogen atom of the carbamate. Enantiomerically pure 1,3‐oxazolidin‐2‐one derivatives can be easily prepared by using enantiomerically pure β‐hydroxyalkyl phenyl selenides as starting materials.
A stereospecific intramolecular nucleophilic substitution of the selenonyl group by the nitrogen atom of the carbamate in a ring‐closure reaction (see scheme; R=Ts or Bz) is the key step in the stereospecific synthesis of 5‐ and 4,5‐substituted‐1,3‐oxazolidin‐2‐ones from β‐hydroxyalkyl phenyl selenides.
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The first example of a kinetic resolution process promoted by electrophilic selenium reagents is reported. Racemic allylic alcohols react with half equivalents of a selenenylating agent in methanol ...leading to the regiospecific formation of the corresponding addition products with a very high level of facial selectivity (from 95:5 to 98:2 dr). The unreacted alcohols can be recovered in an optically enriched form (from 90 to 94% ee).
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Propargylic amines can be valid precursors for the synthesis of beta3-amino acids. This can be effected by a selenium-mediated conversion of the carbon-carbon triple bond to a, Se-phenyl ...selenocarboxylate intermediate. The reactive Se-phenyl selenocarboxylate intermediates can be trapped with water, alcohols, or the amine of an amino acid derivative to give beta3-amino acids, beta3-amino esters, or mixed peptides, respectively.
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Propargylic amines can be valid precursors for the synthesis of β
3
-amino acids. This can be effected by a selenium-mediated conversion of the carbon-carbon triple bond to a, Se-phenyl ...selenocarboxylate intermediate. The reactive Se-phenyl selenocarboxylate intermediates can be trapped with water, alcohols, or the amine of an amino acid derivative to give β
3
-amino acids, β
3
-amino esters, or mixed peptides, respectively.
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