meta-Photoaddition reactions of 2-chloro-, 2,5-dichloro-, and 2-halo-5-isopropyl-tropones with 9,10-dicyanoanthracene

Photoreactions of 2-halotropones with the excited 9,10-dicyanoanthracene gave a meta-adduct and substitution products occurred at the C-2 position of troponoids. The mechanism of the meta-adduct was proved by the product analysis of the reaction of 3,7-dideuterio-2-bromo-5-isopropyltropone and 9,10-dicyanoanthracene. In the photoreaction of 2-chloro-5-isopropyltropone and 9,10-dicyanoanthracene in a mixed solvent of benzene and methanol, a benzaldehyde with a dibenzo-2-oxabicyclo[3.2.2]nonane system was obtained to support occurrence of an [8+4] cycloaddition reaction between them.     

Electrophile and solvent dependent syntheses of cyclic ethers from (z,z)-cycloocta-1,-5-diene

The isomer ratio in the formation of disubstituted 9-oxabicyclo-[4.2.1]nonane and 9-oxabicyclo[3.3.1]nonane derivatives 2 and 3 by an oxyhalogenation procedure depends both on the electrophile and on the solvent utilized.     

SENSITIZED PHOTOOXIDATION OF PINENES BY 9,10-DICYANOANTHRACENE

Abstract —The products of 9,10-dicyanoanthracene sensitized photooxidation of α- and β-pinene were separated and identified. The mechanism of this reaction was investigated by fluorescence spectroscopy, solvent dependence and determination of oxidation potentials of olefins. The formation of an exciplex between excited dicyanoanthracene and pinenes was observed in non-polar solvents. On the bases of these observations, an electron transfer mechanism is proposed for the initial step of this reaction.     

Orbital Unsymmetrization Affects Facial Selectivities of Diels-Alder Dienophiles

We investigated the Diels-Alder reactions of maleic anhydrides embedded in a dibenzobicyclo[2.2.2]octatriene motif as a nonsterically biased dienophile. Substituents on a benzene ring in these dienophiles are far from the reaction center, providing a sterically equivalent pi-face. Instead substituents can unsymmetrize the dienophilic pi face through pi (anhydride)-pi (aromatic) orbital interactions. Electron-withdrawing substituents affect the facial bias and relative rates of these cycloadditions. The preference of the cycloadditions is opposite in direction to those observed in nucleophilic additions of 2-substituted-9,10-dihydro-9,10-ethanoanthracen-11-ones (dibenzobicyclo[2.2.2]octadienones) and in electrophilic additions of 2-substituted 9,10-dihydro-9,10-ethenoanthracenes (dibenzobicyclo[2.2.2]octatrienes), though all of them have related dibenzobicyclic systems.     

TiCl4-promoted tandem carbonyl or imine addition and Friedel-Crafts cyclization: synthesis of benzo-fused oxabicyclooctanes and nonanes

A new and convenient synthesis of benzo-fused 8-oxabicyclo[3.2.1]octane and 9-oxabicyclo[4.2.1]nonane derivatives are described. The reaction involved a TiCl(4)-mediated tandem carbonyl or imine addition followed by a Friedel-Crafts cyclization to provide these functionalized derivatives in good to excellent yields and high diastereoselectivity.     

Indium trichloride mediated intramolecular Prins-type cyclization

[reaction: see text] Intramolecular Prins-type reactions of compounds having both functionalities of homoallyl alcohol and acetal moiety are described. The intramolecular Prins cyclizations were performed using indium trichloride in chloroform or 25% aqueous THF. Both 9-oxabicyclo[3.3.1]nonane and 3,9-dioxabicyclo[3.3.1]nonane compounds were successfully obtained in moderate yields.     

Synthesis of pyrone-annulated 2-oxabicyclo[3.3.1]nonanes by palladium-catalyzed cyclization of 4-hydroxy-2-pyrones with allylic bisacetates

Cyclization of 4-hydroxy-2-pyrones with allylic bisacetates by a palladium catalyst is described. Pyrone-annulated 2-oxabicyclo[3.3.1]nonane derivatives were regioselectively produced from the reaction of 4-hydroxy-2-pyrones with 1,4-diacetoxy-2-cyclohexene at high temperature. The reaction would proceed via a migration of the π-allylpalladium intermediate.     

Oxymercuration. Substituted 9-oxabicyclo[4.2.1]- and 9- oxabicyclo[3.3.1]nonanes

Oxymercuration of cis, cis-1, 5-cyclooctadiene ( 1 ), followed by treatment with potassium iodide and subsequent reaction with iodine, leads to six isomeric diiodides which represent the three possible stereoisomers 2 , 3 , and 4 of 2, 5-diiodo-9-oxabicyclo[4.2.1]nonane as well as 5 , 6 , and 7 of 2, 6-diiodo-9-oxabicyclo[3.3.1]nonane. The isolation, structure determination and some reactions of these diiodo compounds 2 – 7 are described.     

Substituierte 9-Oxabicyclo[4.2.1]- und 9-Oxabicyclo[3.3.1]nonane IV. endo,endo-2,5-Dihydroxy-9-oxabicyclo[4.2.1]nonan,endo, endo-, endo,exo- und exo,exo-2,6-Dihydroxy sowie endo,exo-2,7-Dihydroxy-9-oxabicyclo[3.3.1]nonan; Darstellung und Umwandlungsprodukte

The synthesis of the following compounds and reaction products thereof are described: endo, endo-2,5-dihydroxy-9-oxabicyclo[4.2.1]nonane ( 3–5 ), epimeric 2,6-dihydroxy-9-oxabicyclo[3.3.1]nonanes (endo, endo: 6–8 , exo, exo: 29–32 , and endo, exo: 43–45 ), and endo, exo 2,7-dihydroxy-9-oxabicyclo[3.3.1]nonane ( 46–50 ).     

9,10-Disubstituted octafluoroanthracene derivatives via palladium-catalyzed cross-coupling

9,10-Dichlorooctafluoroanthracene (1) reacts with aryl boronic acids and terminal alkynes under palladium-catalyzed cross-coupling conditions to afford 9,10-diaryloctafluoroanthracenes (2a-e) and 9,10-dialkynyloctafluoroanthracenes (6a,b), respectively. Optical spectroscopy and cyclic voltammetry indicate that octafluoro-9,10-di(thiophen-2-yl)anthracene (2d) exhibits donor-acceptor character and a LUMO energy level of -3.27 eV relative to vacuum. A functionalized 5-bromothiophen-2-yl derivative (2e) was obtained in high yield by bromination of 2d with NBS. X-ray crystallographic analysis of octafluoro-9,10-bis[(trimethylsilyl)ethynyl]anthracene (6a) reveals a solid-state structure that mimics the packing of columnar liquid crystals, with a pi stacking distance of 3.39 A between the octafluoroanthracene cores. In addition, octafluoro-9,10-bis(mesitylethynyl)anthracene (6b) displays a LUMO energy level of -3.50 eV, which approaches the value of -3.65 eV measured for perfluoropentacene, making 9,10-dialkynyloctafluoroanthracenes a promising new class of n-type organic materials.     

Synthesis of perfluorobicyclic ethers [2]. The electrochemical fluorination of α-cyclohexenyl-substituted carboxylic acid derivatives

The electrochemical fluorination of α-cyclohexenyl-substituted carboxylic esters [

; R′CH₃, C₂H₅, C₃H₇)] afforded both perfluoro(9-alkyl-7-oxa-bicyclo[4.3.0]nonane)s and perfluoro(8-alkoxy-9-alkyl-7-oxabicyclo[4.3.0]nonane)s in fairly good yields. As the driving force for the ring-closure in this fluorination, a mechanism which involves a resonance stabilized intermediate radical is proposed. Perfluoro(8-chloro-8-methoxy-9-ethyl-7-oxabicyclo[4.3.0]nonane) and perfluoro(8,8-dichloro-9-ethyl-7-oxabicyclo[4.3.0]nonane) were obtained by the controlled chlorination of perfluoro(8-methoxy-9-ethyl-7-oxabicyclo[4.3.0]nonane) with anhydrous aluminum chloride in low yields. Some new fused perfluorobicyclic ethers and a perfluoroacid fluoride obtained in this experiment have been characterized by infrared, mass and ¹⁹F nmr spectra and elemental analysis.     

The reaction of perfluorobicyclic ethers and perfluorospiro-ethers with anhydrous aluminum chloride

Perfluorobicyclic ethers and perfluorospiroethers, all containing an oxolane skeleton, were treated with AlCl₃ in a heterogeneous manner to give the corresponding α,α,α′-trichlorinated and α,α-dichlorinated products, respectively. From perfluoroacetal compounds, for example, perfluoro(8-methoxy-7-oxabicyclo- [4.3.0]nonane), mono- and di-chlorinated products, i.e. perfluoro- (8-chloro-8-methoxy-7-oxabicyclo[4.3.0]nonane) and perfluoro- (8,8-dichloro-7-oxabicyclo[4.3.0]nonane) were obtained in good yields. The action of fuming sulfuric acid on these polychlorinated products led to the formation of the corresponding lactones. Perfluoro(6-chloro-7-oxa-8-oxobicyclo[4.3.0]nonane) was treated with (CH₃)₂NLi to give N,N-dimethylundecafluoro-2-oxocyclohexyl- acetamide.     

A Stereoselective Synthesis of (±)-cis-γ-Irone

(±)-cis-γ-Irone( 1 ), a main constitutent of natural iris oil, has been stereoselectively synthesized from methyl (2E)-3 -[(2,2,4-trimethyl-3-cyclohexen-1-yl)methoxy]-2-propenoate (3) (6 steps, overall yield 14%). The cis-configuration as the exocyclic position of the double bond of 1 were secured by the thermal ene reaction of the β-(alkenyloxy)acrylate 3 yielding the 3-oxabicyclo [3,3,1] nonane derivative 5 .     

Efficient and stable non-doped deep-blue organic light emitting diode based on an anthracene derivative

A new anthracene derivative 9,10-bis[3,5-di(4-tert-butylphenyl)phenyl]anthracene (BPPA) was synthesized via Suzuki coupling reaction and characterized by 1H NMR spectrum,mass spectrum,and elemental analysis.BPPA exhibits deep-blue emission both in solution and in solid thin film.This compound has a non-planar structure that results in high thermal stability and the phenomenon of polymorphism.The non-doped device based on this material shows stable deep-blue emission with the 1931 Commission international de...     

Scope and applications of second generation palladium-catalyzed cycloalkenylation. Stereoselective total syntheses of isoiridomyrmecin, isodihydronepetalactone, and α-skytanthine

Functionalized bicyclo[3.2.1]octanes, -oxabicyclo-[4.3.0]nonanes, 3-azabicyclo[3.3.0]octanes, and 3-azabicyclo[4.3.0]nonanes were easily synthesized via a second generation palladium-catalyzed cycloalkenylation. Isoiridomyrmecin and isodihydronepetalactone, both of which feature a 3-oxabicyclo[4.3.0]nonane subunit, were stereoselectively synthesized via a second generation palladium-catalyzed cycloalkenylation as the key step. α-Skytanthine, a typical 3-azabicyclo[4.3.0]nonane alkaloid, was also constructed using the same catalytic cyclization protocol.     

Stereoselective synthesis of highly substituted 8-oxabicyclo[3.2.1]octanes and 2,7-dioxatricyclo[4.2.1.03,8]nonanes

The synthesis of new polyhydroxylated 8-oxabicyclo[3.2.1]octanes and 2,7-dioxatricyclo[4.2.1.0^3,8]nonanes is described. These structures is an interesting synthetic blocks for potential bioactive molecules. The precursor, 3-chloro-8-oxabicyclo[3.2.1]oct-6-ene-2,4-dione was obtained from reaction of tetrachlorocyclopropene with furan, then it was involved in carbonyl groups reduction and double bond oxidation, resulted in the formation of a polyhydroxylated derivatives, differently substituted at C-3 position, with five new stereocenters.Using intramolecular transannular hydroxycyclization, bicyclic epoxy diacetate was transformed into 2,7-dioxatricyclo[4.2.1.0^3,8]nonane in high yield through an alkoxide intermediate. Compounds thus obtained have a structure close to certain molecules with antitumor and glycosidase inhibitors activity.     

Marcus theory of outer-sphere heterogeneous electron transfer reactions: dependence of the standard electrochemical rate constant on the hydrodynamic radius from high precision measurements of the oxidation of anthracene and its derivatives in nonaqueous solvents using the high-speed channel electrode

The validity of Marcus theory for outer-sphere heterogeneous electron transfer for the electro-oxidation of a range of anthracene derivatives in alkyl cyanide solvents is investigated. The precision measurement of these fast electron transfers (k(0) >or= 1 cm s(-1)) is achieved by use of the high-speed channel electrode and, where necessary, fast-scan cyclic voltammetry. First, the solvent effect on the rate of electron transfer is studied by considering the first oxidation wave of 9,10-diphenylanthracene in the alkyl cyanide solvents: acetonitrile, propionitrile, butyronitrile, and valeronitrile. Second, the variation of k(0) for a series of substituted anthracenes is investigated by analyzing the voltammetric response of the one-electron oxidations of 9-phenylanthracene, 9,10-dichloroanthracene, 9-chloroanthracene, 9,10-dicyanoanthracene, 9-cyanoanthracene, 9-nitroanthracene, 9,10-diphenylanthracene, and anthracene in acetonitrile. It is shown that the rate of electron transfer of a single compound in different alkyl cyanides is determined by the longitudinal dielectric relaxation properties of the solvent, while differences in rate between the substituted anthracenes in acetonitrile can be quantitatively rationalized by considering their relative hydrodynamic radii. This makes possible the accurate prediction of electron-transfer rates for a molecule by interpolation of rate constants known for related molecules.     

Complete control of regioselectivity in the intramolecular [2 + 2] photocycloaddition of 2-alkenyl-3(2H)-furanones by the length of the side chain

The 2-(omega-alkenyl)-substituted 2-methyl-3(2H)-furanones 2a and 2b were prepared from biacetyl (3) in four reaction steps and in overall yields of 20% and 21%, respectively. They underwent a clean intramolecular [2 + 2] photocycloaddition upon irradiation at lambda = 350 nm. Whereas compound 2a reacted in the expected manner and yielded 7-oxabicyclo[3.2.1.0(3,6)]octane 7 (87% yield), the regioselectivity in the photocycloaddition of compound 2b was completely reversed. The reaction led to compound 8 (92% yield) with the unusual 9-oxabicyclo[4.2.1.0(3,8)]nonane skeleton, the structure of which was established by single-crystal X-ray crystallography.     

Efficient preparation of monoadducts of [60] fullerene and anthracenes by solution chemistry and their thermolytic decomposition in the solid state

The efficient preparation of monoadducts of [60]fullerene and seven anthracenes (anthracene, 1-methylanthracene, 2-methylanthracene, 9-methylanthracene, 9,10-dimethylanthracene, 2,3,6,7-tetramethylanthracene, and 2,6-di-tert-butylanthracene) by cycloaddition in solution is described. The seven mono-adducts of [60]fullerene and the anthracenes were characterized spectroscopically and were obtained in good yields as crystalline solids. The monoadducts of [60]fullerene and anthracene, 1-methylanthracene, 2-methylanthracene and 9,10-dimethylanthracene crystallized directly from the reaction mixture. The thermolytic decomposition at 180 degrees C of the crystalline monoadducts of [60]fullerene and anthracene, 1-methylanthracene, 9-methylanthracene and 9,10-dimethylanthracene all gave rise to the specific formation of a roughly 1:1 mixture of [60]fullerene and the corresponding antipodal bisadducts ("trans-1"-bisadducts) of [60]fullerene and the anthracenes. In contrast, the crystalline monoadducts of [60]fullerene and the anthracene derivatives 2-methylanthracene, 2,3,6,7-tetramethylanthracene and 2,6-di-tert-butylanthracene all decomposed to [60]fullerene and anthracenes (without detectable formation of bisadducts) upon heating in the solid state to temperatures of 180 to 240 degrees C. The formation of the antipodal bisadducts from thermolytic decomposition of crystalline samples of the monoadducts was rationalized by topochemical control.     

Synthesis of bishomoinositols and an entry for construction of a substituted 3-oxabicyclo[3.3.1]nonane skeleton

1,3,3a,7a-Tetrahydro-2-benzofuran was used as key compound for the synthesis of various bishomoinositol derivatives. The diene was subjected to an epoxidation reaction for further functionalization of the diene unit. The bisepoxide obtained was submitted to a ring-opening reaction with acid in the presence of water. Various bishomoinositols were synthesized. However, when the reaction was carried out in the presence of acetic anhydride, a substituted 3-oxabicyclo[3.3.1]nonane skeleton was formed. The mechanism of the formation of the products is discussed.