ESR spectrum of the radical anion of bicyclo[3.2.2]nona-3,6,8-triene-2-one

The radical anion of bicyclo[3.2.2]nona-3,6,8-triene-2-one has been characterised by ESR spectroscopy.     

Polyesters containing bicyclo[2.2.2]octane and bicyclo[3.2.2]nonane rings

Polyesters containing bicyclo[2.2.2]octane and bicyclo[3.2.2]nonane rings are prepared from 1,4-bis(carboethoxy)bicyclo[2.2.2]octane, 1,4-bis(hydroxymethyl)bicyclo[2.2.2]-octane and the 1,5-disubstituted bicyclo[3.2.2]nonane analogs. These polyesters are compared to the related polymers containing 1,4-phenylene and trans-1,4-cyclohexylene rings in terms of their melting point, thermal stabilities and oxidative stabilities. The lower symmetry of the bicyclo[3.2.2]nonane ring produces lower-melting polymers than the other ring systems. The remaining three rings are approximately equivalent in their effect on the melting point of a polymer provided that no more than one bicyclo[2.2.2]octane ring is present per polymer repeat unit. Two such rings produce a highermelting polymer than any other combination. Both the thermal and oxidative stabilities of the polyesters is improved by the presence of the bicyclo rings. This is attributed to the rings providing an approximation of a ladder polymer.     

Synthesis of Si- and N-containing bicyclo[4.2.1]nona-2,4-dienes and bicyclo[4.2.1]nona-2,4,7-trienes

A [6π+2π] cycloaddition of Si- and N-containing alkynes and 1,2-dienes to cyclohepta-1,3,5-trienes in the presence of the two-component catalytic system (acac)₂TiCl₂-Et₂AlCl gives rise to the corresponding bicyclo[4.2.1]nona-2,4-diene and bicyclo[4.2.1]nona-2,4,7-triene derivatives.     

C2-Symmetric bicyclo[3.3.1]nona-2,6-diene and bicyclo[3.3.2]deca-2,6-diene: new chiral diene ligands based on the 1,5-cyclooctadiene framework

As a new type of C₂-symmetric chiral diene ligands, which coordinate to a metal by their 1,5-cyclooctadiene framework, we prepared 2,6-disubstituted bicyclo[3.3.1]nona-2,6-diene (bnd*) and bicyclo[3.3.2]deca-2,6-diene (bdd*), and examined their catalytic activity and enantioselectivity for rhodium-catalyzed asymmetric 1,4-addition to α,β-unsaturated ketones and 1,2-addition to N-sulfonylimines. High enantioselectivity of the Ph-bnd* ligand was observed in the addition of phenylboroxine to N-tosylimine and N-4-nitrobenzenesulfonylimine of 4-chlorobenzaldehyde to give phenyl(4-chlorophenyl)methylamines in high enantiomeric excess (98–99% ee).     

Enantiomerically pure bicyclo[3.3.1]nona-2,6-diene as the sole source of enantioselectivity in BIPHEP-Rh asymmetric hydrogenation

In situ resolution of the rapidly racemising diphosphine BIPHEP and its relatives with the cationic Rh complex of (S,S)-bicyclonona-2,6-diene permits the asymmetric hydrogenation of dehydroamino esters.     

Valence isomerization of C9H10hydrocarbons: Photochemical reactions of bicyclo [3.2.2] nona-2,6,8-triene and its dihydro-derivatives

The valence isomerization reaction of bicyclo[3.2.2]nona-2,6,8-triene ($\text{2}$), which photoisomerized to two homologues of semibullvalene, was discussed with the photoreactions of its dihydro-dreivatives, bicyclo[3.2.2]nona-6,8-diene ($\text{3}$) and bicyclo[3.2.2]nona-2,6-diene ($\text{4}$).     

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.     

Organosilicon chalcogenides with trisilane units - bicyclo[3.3.1]nonanes, bicyclo[3.2.2]nonanes and spiro[4.4]nonanes

Treatment of 1,2,3-trichloropentamethyltrisilane (1) with H₂S/NEt₃ results in the formation of a mixture of two isomers of (Me₅Si₃)₂S₃ with a bicyclo[3.3.1]nonane (2a) and a bicyclo[3.2.2]nonane (2b) skeleton, while the reaction of 1 with Li₂Se yields one product only, (Me₅Si₃)₂Se₃ (3a), with a bicyclo[3.3.1]nonane structure. Besides ¹H, ¹³C, ²⁹Si and ⁷⁷Se NMR spectroscopy 3a has also been characterized by a crystal structure analysis.Compounds Si(SiMe₂EMR₂E)₂ (5a-h: MR₂: SiMe₂ (5a, c, d), SiPh₂ (5b), GeMe₂ (5e, f), SnMe₂ (5g, h); E=S (5a, b, e, g), Se (5c, f, h), Te (5d)) with a spiro[4.4]nonane skeleton have been obtained in mixture with varying amounts of the corresponding six-membered rings (R₂ME)₃ by reactions of mixtures of 1,2,2,3-tetrachlorotetramethyltrisilane (4) and diorganodichlorosilanes, Me₂GeCl₂ or Me₂SnCl₂, with H₂S/NEt₃, Li₂Se or Li₂Te and have been characterized in situ by multinuclear NMR spectroscopy (¹H, ¹³C, ²⁹Si, ¹¹⁹Sn, ⁷⁷Se, ¹²⁵Te) and GC-MS.     

2,3,7,8-Tetraazaspiro[4.4] nonane, 2,3,7,8-tetraazaspiro-[4.4] nona-2,7-diene and derivatives

Synthetic routes to the title compounds ( 4, 12 ) are described. Chiral derivatives of these, 2,7-bis(phenylcarbamoyl)-2,3,7,8-tetraazaspiro[4.4]nonane ( 7 ) and 3,8-dicarbomethoxy-2,3,7,8-tetraazaspiro[4.4]nona-1,6-diene ( 10 ) were prepared. Synthetic routes to diketo derivatives of other tetraazaspiro[4.4]nonanes were explored. 3,3-Dicarbethoxy-1-pyrazoline ( 24 ) and 3,3-dicarbethoxypyrazolidine ( 25 ) were prepared and their reactions with hydrazine examined. Proton and ¹³C nuclear magnetic resonance spectra of new compounds, including some 5-substituted 3-hydroxypyrazoles, are discussed in relation to structure.     

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.     

Stereoelectronic control of the retro diels–alder reaction in 8-(N-pyrrolidyl)bicyclo[4.3.0]nona-3,7-diene isomers

The cis- and trans-annulated isomers of 8-(N-pyrrolidyl)bicyclo[4.3.0]nona-3,7-diene show different propensities for the retro Diels–Alder fragmentation following electron impact ionization. Molecular ions of the cis-annulated isomer decompose predominantly via the retro Diels–Alder reaction to give [C₉H₁₃N] ⁺· fragments of the appearance energy (AE)=8.45±0.05eV and critical energy E_c=133±8kJ mol^?1. The trans-annulated isomer gives abundant [M–H]⁺ (AE=9.34±0.08eV) and [M–C₆H₆]⁺· fragments, in addition to [C₉H₁₃N]⁺· ions of AE=8.98±0.05eV and E_c=181±8kJ mol^?1. The ionization energies (IE) were determined as IE_cis=7.07±0.05 eV and IE_trans=7.10±0.06eV. The stereochemical information is much less pronounced in unimolecular decompositions of long-lived (metastable) molecular ions which show very similar fragmentation patterns for both geometrical isomers. Nevertheless, the isomers exhibit different kinetic energy release values in the retro Diels–Alder fragmentation; T_0.5=3.8±0.3 and 4.8±0.2 kJ mol^?1 for the cis and trans isomer respectively. Topological molecular orbital calculations indicate that the retro Diels–Alder reaction prefers a two-step path, with a subsequent cleavage of the C(5)? C(6) and C(1)? C(2) bonds. The open-ring distonic intermediate represents the absolute minimum on the reaction energy hypersurface. The cleavage of the C(1)? C(2) bond is the rate-determining step in the decomposition of the cis isomer, with the critical energy calculated as 137 kJ mol^?1. The cleavage of the C(5)? C(6) bond becomes the rate-determining step in the trans-annulated isomer because of stereoelectronic control. The difference in the energy barriers to this cleavage in the isomers (ΔE=95k Jmol^?1) provides a quantitative estimate of the magnitude of the stereoelectronic effect in cation radicals.