Reactions of α,β-unsaturated ketones of the bicyclo[3.3.1]nonane series with nitro alkanes

Reaction of bicyclo[3.3.1]nona-3,7-diene-2,6-dione with nitroform in boiling methanol occurs with involvement of the solvent and results in 2,6-dimethoxy-4,8-bis(trinitromethyl)-bicyclo[3.3.1]nona-2,6-diene, while the reaction in tert-butyl alcohol affords 4,8-bis(trinitromethyl)bicyclo[3.3.1]nona-2,6-dione.     

Synthesis of 4′-alkyl-8-azaspiro[bicyclo[3.2.1]octane-3,2′-morpholin]-5′-ones

N-Boc-protected 8-azaspiro[bicyclo[3.2.1]octane-3,2′-oxirane] reacted with primary aliphatic amines through opening of the epoxide ring with formation of the corresponding amino alcohols which were converted into N-chloroacetyl derivatives. The latter underwent cyclization to N-Boc-protected 4′-alkyl-8-azaspiro[bicyclo[3.2.1]octane-3,2′-morpholin]-5′-ones by the action of sodium hydride in DMF, and subsequent treatment with hydrogen chloride in ethyl acetate afforded 8-azaspiro[bicyclo[3.2.1]octane-3,2′-morpholin]-5′-one hydrochlorides.     

Enantioselective intramolecular cyclopropanation of α-diazo-β-keto sulfones: asymmetric synthesis of bicyclo[4.1.0]heptanes and tricyclo[4.4.0.0]decenes

Catalytic asymmetric synthesis of some new chiral building blocks useful for natural product synthesis is described. The intramolecular cyclopropanation (IMCP) reaction of α-diazo-β-keto sulfones affording bicyclo[4.1.0]heptanes such as 9a-d is found to proceed with high enantioselectivity (93-98% ee). The yield is moderate due to the competing intramolecular C-H insertion reaction. As intramolecular C-H insertion reaction is not observed in the reaction of the substrates possessing a quaternary carbon at the allylic position, the reactions of 19a and 19b proceed with high enantioselectivity (95% ee) and yield. It was also found that the substrates possessing an ether group, such as 19a and 19b, could be used in this enantioselective IMCP reaction.     

A new approach to the bicyclo[3.3.1]nonane framework of huperzine A-like molecules via palladium-catalyzed intramolecular γ-arylation

In our synthetic studies toward huperzine A, a diastereoselective α′-alkylation of the α-amido-γ-methyl hexenone 4 was realized through a dianion intermediate which significantly enhanced the reactivity. Under the attempted Heck reaction conditions, an unexpected and unprecedented palladium-catalyzed intramolecular γ-arylation of 3 was observed, which generated 18 with bicyclo[3.3.1]nonane framework in satisfactory yield.     

Synthesis of bicyclo[3.1.0]hexanones via 1,3-dipolar cycloaddition of diazoalkanes to homochiral α-sulfinyl-2-cyclopentenones

The reactions of diazomethane, diazoethane, and (trimethylsilyl)diazomethane with (S)-2-p-tolylsulfinylcyclopent-2-en-1-one have been studied. The sulfinyl group increases the reactivity and controls the π-facial and endo/exo selectivities. The π-facial selectivity can be inverted in the presence of Yb(OTf)₃, which makes possible the stereodivergent synthesis of both diastereoisomeric pyrazolines. Completely stereoselective denitrogenation of optically pure pyrazolines into cyclopropanes was achieved under substoichiometric Yb(OTf)₃ catalysis.     

1H NMR study of inclusion of substituted bicyclo[3.3.1]nonanes in α- and β-cyclodextrins

The interaction of 2,6-disubstituted bicyclo[3.3.1]nonanes with - and -cyclodextrins has been investigated by¹H NMR spectroscopy and the formation of (11) host—guest complexes has been established.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2523–2525, December, 1995.     

Stereoselective [4+2] cycloadditions of tetrazines to 3-oxo- and 3-arylimino-4′-methylenedihydro-3′H-spiro[bicyclo[2.2.1]heptane-2,2′-furans]

Stereoselective inverse-demand [4+2] cycloadditions of 3,6-bis(pyridin-2-yl)-1,2,4,5-tetrazine and dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate to 4′-methylenedihydro-3′H-spiro[bicyclo[2.2.1]heptane-2,2′-furans] and 4′-methylene-1′-(4-nitrophenyl)spiro[bicyclo[2.2.1]heptane-3,2′-pyrrolidine] were studied. Cycloadditions took place stereoselectively at the exocyclic CC double bonds to give novel 11:14-isopropylidene-14-methyl-2,3-diaza-8-oxadispiro[5.1.5.2]pentadecane and 11:14-isopropylidene-11-methyl-2,3,8-triazadispiro[5.1.5.2]pentadecane derivatives in 50–98% de. The structures of the novel dispiro compounds were determined by NMR techniques, NOESY spectroscopy and X-ray diffraction.     

Microwave‐Assisted Beckmann Rearrangement: Convenient Synthesis of 1,3‐Diaza‐bicyclo[3.2.2]nonane

Small heterocyclic amines such as 1,3‐diaza‐bicyclo[3.2.2]nonane are known to be key components of biologically active molecules. A convenient synthesis of this compound utilizing a key Beckmann rearrangement of (Z)‐1‐aza‐bicyclo[2.2.2]octan‐3‐one oxime (6) with conc. H₂SO₄ under microwave irradiation was achieved. The desired compound (1) was obtained in 20% yield overall.     

Conversion of γ-substituted bicyclo[2.2.1] (Z)-vinylsulfones to the corresponding (E)-allylsulfones

The preparation of bicyclo[2.2.1] (E)-allylsulfones starting from the corresponding (Z)-vinylsulfones is described. Starting from 2,3-bis(phenylsulfonyl)norbornadiene 1, the Michael addition of organometallic reagents followed by the base catalyzed isomerization affords (E)-allylsulfones in high yields. The procedure allows to obtain vinylidenic norbornenes which are characteristic nuclei of valuable biologically active compounds.     

Novel Method for the Synthesis of [1,2,4]Triazino[4,3‐c]quinazoline System

4‐Hydrazinoquinazoline was found to form new 2‐(3,4‐dihydro‐3oxo‐2H‐[1,2,4]triazino[4,3‐c]quinazolin‐4‐yl)acetic acid with maleic anhydride in on‐step sequence. Proposed heterocyclization includes, probably, acylation reaction followed by intramolecular uncleophilic addition.     

Spectrophotometric study of melting of double stranded Poly[A]·Poly[U] in the aqueous solution

Experimentally observed changes in the electronic absorption spectrum of sodium salt of synthetic polyadenyl–polyuridyl acid (Poly[A]·Poly[U]) in the aqueous solution (pH = 7.0, I = 0.15 mol/L) with the change in temperature were explained in terms of co-existence of two different forms of the Poly[A]·Poly[U] strands. Chemometrics analysis of full set of melting curves measured at 120 wavelengths in the UV spectral range has been performed using evolving factor analysis (EFA) and KALS designed for the calculation of equilibrium constants from spectrometry data without a priori set model of the system. Using the Van’t Hoff equation, we have determined thermodynamic constants of the biopolymer transition from the double stranded helix into the random coil conformation (helix–coil transition), they can be further used to quantify the possibility of these structures to be involved in biochemical processes. Molecular model of partially denatured Poly[A]′·Poly[U]′ complex has been biult by means of molecular mechanics.     

Synthesis of 2-substituted 6,8-dinitro[1,2,4]triazolo[1,5-a]pyridines and the formation of the related zwitterionic σ-adducts

A method for the synthesis of 2-substituted 6,8-dinitro[1,2,4]triazolo[1,5-a]pyridines is proposed. The method includes the reaction of 2-chloro-3,5-dinitropyridine with the corresponding 5-substituted tetrazoles. The resulting compounds react with anhydro bases of α- and γ-methylazinium salts to give zwitterionic σ-adducts. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1405–1407, July, 1999.     

Stereoselectivity of the captodative alkenes 1-acetylvinyl arenecarboxylates in Diels-Alder reactions with cyclic dienes and stereospecific rearrangement of their bicyclo[2.2.n] α-ketol adducts

Captodative alkene 1-acetylvinyl p-nitrobenzenecarboxylate 1a was evaluated for its reactivity and stereoselectivity with cyclohexadiene (10) in Diels-Alder reactions, showing exclusive endo preference. The two hydrolyzed products of the endo and the exo adducts obtained from the Diels-Alder cycloaddition between 1a and cyclopentadiene (7) were 8b and 9b. When treated with mCPBA, a ring expansion took place to stereospecifically yield the novel 3-oxatricyclo[3.3.1.0^2,4]nonanone acyloins 15 and 16, respectively. In the case of the α-ketol bicyclo[2.2.2]octanes 11b and 12b, the epoxidation/Baeyer-Villiger cascade process was preferred, resulting in the syn ketoepoxide 19b from each isomer. A synthetic application of this kind of transformation was carried out by reacting ketols 8b and 9b with an excess of mCPBA through a five-step cascade process to yield the bicyclic lactone 27 as a potential precursor of racemic β-carbaxylose.     

Cyclopenta[b]thienyl ligand in organometallic chemistry. Studies of the regioselectivity of the synthesis of new σ-element-substituted cyclopenta[b]thiophene derivatives

Reactions of 2-ethyl-5-methylcyclopenta[b]thienyllithium (thiopentalenyllithium) (2) with various electrophilic reagents afford σ-element-substituted thiopentalenes. However, the reaction with Ph₃SnCl yields only one of two possible isomers,viz, triphenyl(4H-cyclopenta[b] thiophen-4-yl)stannane (4c), whereas the reactions with Me₃SiCl, Me₃SiCl, or Ph₂PCl give both possible isomers,viz., trimethyl(6H-cyclopenta[b]thiophen-6-yl)silane (3a) and trimethyl(4H-cyclopental[b]thiophen-4-yl)silane (4a), trimethyl(6H-cyclopenta[b]thiophen-6-yl)stannane (3b) and trimethyl(4H-cyclopental[b]thiophen-4-yl)stannane (4b), or diphenyl(6H-cyclopenta[b]thiophen-6-yl)phosphine (3d) and diphenyl(4H-cyclopenta[b]thiophen-4-yl)phosphine (4d) in ratios of 1∶2, 1∶2, or 1∶1, respectively. The structure of compound4c was established by X-ray diffraction analysis. The observed regioselectivity of formation of compound4c is attributed to the specific precoordination of the tin atom by the sulfur atom of the thiopentalenyl ligand and to the steric overcrowding of the Sn atom in organotin electrophiles. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1285–1289, July, 2000.     

Tetraviologen calix[4]resorcine as a mediator of the electrochemical reduction of [PdCl4]2– for the production of Pd0 nanoparticles

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Theoretical Study of the Photochemical Reaction Mechanism of Bicyclo [4.1.0 ] heptane

IntroductionPhotochemical reactions, which involve a three-membered ring, have been of great interest to experi-mental photochemists[1—10]. A main reason for thisphenomenon is that the cyclopropane ring exhibits somereaction characteristics of double bon…     

Synthesis of endo,exo-7,8,9,10-tetrachlorobicyclo[4.4.0]deca-7,9-diene-3,4-dicarboxylic acid N,N′-bisimides

A one-stage synthesis was developed of N,N′-(3,3′-dimethoxy-4,4′-diphenylmethane)- and N,N′-(1,2-ethane)-endo,exo-7,8,9,10-tetrachlorobicyclo[4.4.0]deca-7,9-diene-3,4-dicarboxylic acids bisimides by reaction of a bisadduct of 1,8,9,10,11,11-hexachlorotricyclo[6.2.1.0^5,10]-undec-9-ene-4,5-dicarboxylic acid N,N′-R-bisimide with pyridine in DMF. The spatial structure of compounds obtained was established.     

Synthesis and Transformation of 5- and 2-Methyl- bicyclo[2.2.1]hept-2-enes and 2-Methylenebicyclo[2.2.1]heptane with Retrospective δ-Migration of Hydrogen over Oxide Catalyst

5-, 2-Methylbicyclo[2.2.1]hept-2-enes, 2-methylenebicyclo[2.2.1]heptane were synthesizedby a new procedure, and their transformations in a flow system over stationary layer of aluminosilicatecatalyst were studied at various temperatures. At 150-400°C these compounds undergo isomerization which is accompanied by -migration of hydrogen. The isomerization mechanism is discussed in terms of formation of classical carbocations, not invoking nonclassical carbenium ion.     

Elysiapyrones from Elysia diomedea. Do such metabolites evidence an enzymatically assisted electrocyclization cascade for the biosynthesis of their bicyclo[4.2.0]octane core?

[structure: see text] Biogenetically interesting polypropionate-derived metabolites 1 and 2, featuring an unprecedented skeleton, have been isolated from the sea slug Elysia diomedea. Their enantiomeric character indicates that the current spontaneous electrocyclization cascade biogenetic hypothesis for the bicyclo[4.2.0]octane core must be enzymatically aided. These compounds are isomeric with the 15-nor-9,10-deoxytridachione/15-norphotodeoxytridachione pair of metabolites and encourage speculation about their biosynthetic relationship.     

Intramolecular Ullmann-type C−N coupling for the synthesis of substituted benzo[4,5]imidazo[1,2-a]pyrrolo[3,4-c]pyridines

An efficient CuI catalyzed intramolecular Ullmann-type C−N coupling reaction is described here. Newly substituted 1H-benzo[4,5]imidazo[1,2-a]pyrrolo[3,4-c]pyridine-1,3,5(2H, 11H)-trione has been easily synthesized from ortho halogenated N-substituted pyrrolo[3,4-c]pyridine-1,3,6(5H)-triones in presence of CuI catalyst and K₂CO₃ base without any ligand. This procedure is based on intramolecular Ullmann-type reaction and provides a proficient method of making fused tetracyclic heterocycles.