Rhodium-catalyzed asymmetric arylative ring opening of bicyclic hydrazines

The development of a novel asymmetric ring opening of bi- and polycyclic hydrazines with aryl organometallic reagents is presented. The application of this reaction to the most simple bicyclic hydrazine 1a gives a straightforward regio- and diastereoselective access to synthetically useful trans 3,4-disubstituted hydrazinocyclopentenes in an enantioenriched form.     

Enantioselective haloetherification by asymmetric opening of meso-halonium ions

A new approach to enantioselective haloetherification reactions via desymmetrization of in situ-generated meso-halonium ions is described. The combination of N-haloamides as a halogen source and sodium salts of chiral phosphoric acids as catalysts can be used for the cyclization of symmetrical ene-diol substrates, yielding the haloetherification products under practical conditions in enantioenriched form.     

The generation and properties of episulfonium intermediates. 8. Regioselectivity in the nucleophilic ring opening of episulfonium ion derivatives of some unsymmetrical alkyl- and arylolefins

Conclusions The ring opening of episulfonium complex derivatives of trimethylethylene, styrene, and 2,3,4,5,6-pentafluorophenylethylene proceeds with the predominant formation of adducts according to the Markownikoff rule, while this reaction yields comparable amounts of the regioisomers for isopropylethylene.Communication 7: [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2521–2526, November, 1979.     

Iridium-catalyzed asymmetric ring opening of azabicyclic alkenes by amines

The enantioselective ring-opening reactions of azabicyclic alkenes with primary and secondary aromatic amine nucleophiles are reported using an iridium catalyst generated in situ from 1.5 mol % of [Ir(COD)Cl](2) and 3 mol % of (S)-BINAP. The reaction affords the corresponding trans-1,2-diamine derivatives in moderate to good yields with moderate to high enantioselectivities (up to 97% ee). The trans-configuration of the 1,2-diamino product 2g was confirmed by X-ray crystallography.     

Rhodium-catalyzed asymmetric ring opening of oxabicyclic alkenes with phenols

The scope of the rhodium-catalyzed asymmetric ring opening reaction of oxabenzonorbornadiene has been extended to include phenolic nucleophiles. The enanatioenriched, functionalized dihydronaphthalene products are highly valuable intermediates for which no other practical methods of preparation are available. A new catalyst system has been developed which allows the use of less reactive o-halophenols. The utility of these products has been demonstrated through their application in the synthesis of benzofuran polycyclic materials.     

Rhodium-catalyzed asymmetric ring opening of oxabicyclic alkenes with organoboronic acids

The first rhodium(I)-catalyzed asymmetric addition of organoboronic acids to oxabicyclic alkenes is reported. This asymmetric ring-opening (ARO) reaction can proceed in high yield under very mild conditions with electronically diverse organoboronic acids, in a highly diastereoselective and enantioselective manner. [structure: see text]     

N-Methylative aziridine ring opening and asymmetric synthesis of MeBmt

Asymmetric synthesis of MeBmt, an unusual amino acid constituent of cyclosporine A, was achieved from aziridine-(2R)-carboxaldehyde through the highly stereoselective addition of (E)-crotylboronate and the subsequent N-methylative aziridine ring opening as key steps.     

Copper-catalyzed asymmetric ring opening of oxabicyclic alkenes with organolithium reagents

A highly efficient method is reported for the asymmetric ring opening of oxabicyclic alkenes with organolithium reagents. Using a copper/chiral phosphoramidite complex together with a Lewis acid (BF(3)·OEt(2)), full selectivity for the anti isomer and excellent enantioselectivities were obtained for the ring opened products.     

Rhodium-catalyzed asymmetric ring opening of oxabicyclic alkenes with sulfur nucleophiles

The synthesis of 2-sulfanyl-1,2-dihydro-naphthalen-1-ols is described. This methodology is based on rhodium catalysis and enables various thiols to undergo an asymmetric SN2' ring opening of oxabenzonorbornadiene. Under the reaction conditions ([Rh(COD)Cl](2) (2.5 mol %), (S)-(R)-PPF-P(t)Bu(2) (6 mol %), AgOTf (7 mol %), NH(4)I (1.7 equiv), galvinoxyl (5 mol %), THF, 85 degrees C), aryl- and alkyl-sulfide adducts are obtained in good to excellent yield and in high enantiomeric excess (>90% ee).     

Rhodium-catalyzed asymmetric ring opening of azabenzonorbornadiene with substituted piperazine nucleophiles

We have developed an asymmetric ring opening reaction of azabenzonorbornadiene with substituted piperazine. By increasing the amount of catalyst (from 2.5 to 5%) and ligands (5 to 10%) as well as addition of ammonium iodide, the products can be obtained in high yield and the reaction time shortened dramatically, but the ee values were rather low.     

Copper-catalyzed asymmetric ring opening of oxabicyclic alkenes with Grignard reagents

[reaction: see text] Simple Grignard reagents were applied in copper-catalyzed asymmetric ring-opening reactions of oxabenzonorbornadiene derivatives using spiro phosphoramidite ligands. Excellent anti-stereoselectivities and good enantioselectivities were achieved.     

Catalytic asymmetric ring opening of meso-epoxides with aromatic amines in water

[reaction: see text] An operationally simple and environmentally benign protocol for the catalytic asymmetric ring opening of meso-epoxides with aromatic amines has been developed. The reactions proceeded smoothly in the presence of 1 mol % of Sc(OSO3C12H25)3 and 1.2 mol % of a chiral bipyridine ligand in water to afford beta-amino alcohols in high yields with excellent enantioselectivities.     

Cr(salen) catalysed asymmetric ring opening of monocyclic terpene-epoxides

The racemic Cr^III(salen) complex was found to be an efficient catalyst for the asymmetric ring opening (ARO) with TMSN₃ of cyclic 1,2-epoxy-terpenes bearing C₄-substituents.     

Generation and properties of episulfonium intermediates. 7. Generation of episulfonium ions from 1,3-butadiene and isoprene

Conclusions It has been shown to be possible to generate episulfonium intermediates by reacting divinyl or isoprene with a variety of arylsulfenyl cations. The formation of these intermediates and their reaction with the acetate anion occurs with strict regioselectivity, attacking only one of the double bonds of the diene system.For part 6, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2300–2306, October, 1979.     

Alkylative ring opening of N-methylaziridinium ions and a formal synthesis of tyroscherin

Alkylative ring-opening reactions of stable 2-substituted N-methylaziridinium ions proceeded with various alkyl- or arylmagnesium bromides in the presence of CuI to yield synthetically valuable and optically pure alkylated acyclic amines in a completely regio- and stereoselective manner. This was applied to a formal synthesis of the cytotoxic natural product tyroscherin.     

Highly enantioselective catalytic asymmetric ring opening reaction employing the Daniphos ligand

A set of the recently published planar-chiral Daniphos diphosphine ligands, based on an arene chromium tricarbonyl scaffold, has been applied to the rhodium-catalyzed asymmetric ring opening (ARO) reaction of 1,4-dihydro-1,4-epoxynaphthalene with methanol as the nucleophile. Enantioselectivities of up to 97.5% ee at satisfactory conversions have been obtained. The most successful ligand showed to be a PPh₂/P(t-Bu)₂-substituted derivative. An X-ray structure of this ligand is presented and discussed.     

Generation and properties of episulfonium intermediates communication 5. Stereochemistry of formation and opening of episulfonium complexes obtained from cis- and trans-butenes

Conclusions It was shown that stable intermediates of the type of episulfonium ions can be generated by the reaction of the cis- and trans-butenes with the 2,4-dinitrophenylsulfene and p-chlorophenylsulfene hexafluoroantimonates. The stereochemistry of the formation and opening of these intermediates was established, and also the conditions of their cis-trans interconversions.See [1] for Communication 4.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2743–2749, December, 1976.