Synthesis of a chiral tricyclo[5.2.1.02.6]-deca-4,8-dien-3-one

In recent years we have been interested in the synthesis of natural products by retro Diels-Alder reaction.~(1-4)A rogod ,p;eci;e tricyclo[5.2.1.0~(2.6)-deca-4,8-dien-     

Addition of dichlorocarbene to tricyclo[4.3.0.03,7]nona-4,8-diene

Addition of dichlorocarbene to tricyclo[4.3.0.0^3,7]nona-4,8-diene (brexadiene) under conditions of phase transfer catalysis occurs from theexo side. Cyclopropyl-allyl rearrangement of intermediate chlorocyclopropanes yields tricyclo[5.4.0.0^3,8]undecadienes. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 8, pp. 1494–1497, August, 1997.     

Ion-molecule reactions and thermal isomerization of tricyclo[4.3.0.0]nona-4,8-diene radical cations to tricyclo[4.2.1.0]nona-2,7-diene radical cations in a γ-irradiated frozen Freon matrix

A four-step mechanism of isomerization of tricyclo[4.3.0.0^3,7]nona-4,8-diene radical cations to tricyclo[4.2.1.0^4,9]nona-2,7-diene radical cations in γ-irradiated frozen Freon-113 (CFCl₂CF₂Cl) matrix was suggested on the basis of ESR data. The rearrangement was found to occur via distonic form of the radical cations with spin and charge separation. Furthermore, it was shown that the primary radical cations abstracts hydrogen atom from methylene group of the parent molecule, whereas distonic radical cations reacts via attachment to the C=C bond at 110–119 K.     

Hexamethyl(Dewar Benzene) (Hexamethylbicyclo[2.2.0]hexa-2,5-diene)

Hexamethyl(Dewar benzene) was first obtained by bicyclotrimerization of 2-butyne in the presence of aluminum chloride. This preparation provided a basis for a comprehensive study of the chemical reactivity of Dewar benzene derivatives. Interesting information concerning the reactivity of the permethylated Dewar benzene system can be deduced from its behavior on hydrogenation and oxidation, and, in particular, from the addition of H-acidic compounds and from the substitution and elimination reactions of the resulting adducts.     

Enzymatic desymmetrization of prochiral 2,3-bis(acetoxymethyl)bicyclo[2.2.1]hepta-2,5-diene and 2,3-bis(hydroxymethyl)bicyclo[2.2.1]hepta-2,5-diene

Enzymatic desymmetrization of the title compound 1 is reported using various commercially available lipases in hydrolysis and alcoholysis reactions or ester synthesis. In this area, lipase Amano AK (Pseudomonas sp.) proved to be the best lipase whatever the experimental conditions used. The monoacetate product 2 is indifferently obtained with more than 95% enantiomeric excess (ee) as the levorotatory enantiomer 2a or the dextrorotatory one 2b.     

Ring-opening reactions of spiro[2.4]hepta-4,6-diene and spiro[4.4]nona-1,3-diene induced by tungsten(0) carbonyls

Tungsten(0) carbonyls react with the strained spiro[2.4]hepta-4,6-diene and the less strained spiro[4.4]nona-1,3-diene with CC bond cleavage and formation of stable alkylene bridged π-cyclopentadienyl-σ-alkyl complexes. The product containing a two carbon bridge has the same unusual spectroscopic properties as the analogous molybdenum complex.     

The Radical Cations of Bicyclo[2.2.1]hepta-2,5-diene (8,9,10-Trinorborna-2,5-diene) and bicyclo[2.2.2]octa-2,5-diene (2,3-Dihydrobarrelene). An ESR and ENDOR study

The radical cation of bicyclo[2-2.1]hepta-2,5-diene (8,9,10-trinorborna-2,5-diene; 1 ) in CF₂ClCFCl₂, and CF₃CCl₃ matrices and that of bicyclo[2.2.2]octa-2,5-diene (2,3-dihydrobarrelene; 2 ) in CFCl₃ and CF₃CCl₃ matrices have been studied by ESR and ENDOR spectroscopy. For ${\bf 1}^{+ \atop \dot{}}$, the coupling constants of the olefinic, methano-bridge, and bridgehead protons are ?0.780 ±0.005, +0.304±0.002, and ?0.049±0.002 mT, respectively. The hyperfine tensor for the methano-bridge protons is axial, A_x = +0.263 ± 0.002 and A_y = +0.386 ± 0.002 mT, while that for the olefinic protons is orthorhombic, A_x = ?0.594 ± 0.005, A_y= ?0.913 ± 0.005, and A_z = ?0.834 ± 0.005 mT (x parallel to C? H- z parallel to 2p_π axis). For ${\bf 2}^{+ \atop \dot{}}$, the coupling constants of the olefinic, ethano-bridge, and bridgehead protons are ?0.68 ± 0.01, +0.162 ± 0.005, and ?0.108 ± 0.005 mT, respectively. The hyperfine data for ${\bf 1}^{+ \atop \dot{}}$ and ${\bf 2}^{+ \atop \dot{}}$ fully support the presentation of their singly occupied orbitals as antisymmetric combinations, b₂(π), of the two bonding ethene π-MO's.     

Isolation of o-xylylene (o-quinodimethane) dirivatives. A strong through-bond interaction in 2,3-benzobicyclo[2.2.0]hexane system

Some o-xylylene (o-quinodimethane) derivatives were isolated as stable cyrstalline materials. A strong through-bond interaction in tetracyanoethylene addition product of tetraphenylbenzodicyclobutadiene ($\text{21}$ is suggested.     

Cyclopolymerization of (E,E) - [6.2]paracyclophane-1,5-diene

Polymerization of (E,E)-[6.2]paracyclophane-1,5-diene proceeds by an intra–intermolecular mechanism to give a polymer containing a [3.2]paracyclophane in the repeat unit. Polymerization occurs with either free radical or cationic initiation; anionic initiation was unsuccessful. Cationic polymerization is favored and appears to proceed through a stabilized carbonium ion intermediate. Spectroscopic and model compound studies are consistent with the proposed polymer structure. Thermal analyses of the polymer indicate a complex thermooxidative behavior in the presence of oxygen, while depolymerization occurs above about 400°C in an inert atmosphere.     

Cobalt(III) complexes of 2-oximino-10-oximino-3,9-dimethyl-4,8-diazaundeca-3,8-diene

Summary The pseudo-macrocyclic dioxime ligand [(1) = LH] has been synthesized. A variety of cobalt(III) complexes, trans-[CoLX₂], have been prepared and characterized (X = Cl, Br, NO₂, NCS or N₃) and [CoLCl(NO₂)]. Vis. and i.r. spectra of the complexes are reported and aspects of the solution chemistry of the complexes studied.     

Photochemical isomerization of 1,2,5-trisilabicyclo[3.2.0]hepta-3,6-diene to 1,4,7-trisilabicyclo[2.2.1]hepta-2,5-diene

Upon irradiation of a benzene-d6 solution of 1,2,2,5-tetrakis[di-tert-butyl(methyl)silyl]-4,7-diaryl- 1,2,5-trisilabicyclo-[3.2.0]hepta-3,6-diene [1a: aryl = phenyl, b: aryl = 3,5-bis-(trimethylsilyl)phenyl], 1,4,7,7-tetrakis[di-tert-butyl-(methyl)silyl]-2,5-diaryl-1,4,7- trisilabicyclo[2.2.1]hepta-2,5-diene (2a,b) was formed via skeletal rearrangement.     

Tetracyclo[5.3.0.02,803,6]deca-4,9-diene. A new (CH)10 hydrocarbon

Irradiation of tricyclo[5.3.0.0^2,8]deca-3,5-dien-9-one ethylene acetal yields tetracyclo[5.3.0.0^2,80^3,6]dec-4-en-9-one ethylene acetal as main product which can be converted to the title compound, a new (CH)¹⁰ hydrocarbon.