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.     

Dimerization of bicyclo[2.2.1]hepta-2,5-diene in the presence of rhodium carboxylate complexes

Conclusions Bicyclo [2.2.1]hepta-2,5-diene (norborndiene) dimerizes in the presence of Rh (II) carboxylate complexes Rh₂(RCOO)₄ (R=CH₃, CF₃) at 25–100°C to form preferentially the products of (4+2) cycloaddition. The rate of the reaction in the presence of Rh₂ (CF₃COO)₄ is an order of magnitude higher than for Rh₂(CH₃COO)₄. Under the reaction conditions Rh(II) is reduced by norbornadiene to Rh(I).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 635–639, March, 1982.     

2,3-Dichlorobicyclo[2.2.1]hepta-2,5-diene: A Convenient Precursor of Norbornadiene-2,3-diynes

Norbornadienes that feature the properties of norbornadiene and of the ene-diyne in the same molecule have been prepared via a simple and high-yielding route starting fromdichlorobicyclo[2.2.1]hepta-2,5-diene (1).     

Desymmetrization of meso 7-aza-2,3-bis(phenylsulfonyl) bicyclo[2.2.1]hept-2-ene: a re-examination. Kinetic resolution of racemic 3-arylsulfonyl-7-aza-2-bromobicyclo[2.2.1]hepta-2,5-dienes

The inexpensive large scale preparation of N-methoxycarbonyl-7-aza-2,3-bis(phenylsulfonyl)bicyclo[2.2.1]hept-2-ene and the re-examination of its stereoselective desymmetrization are reported. Moreover, the kinetic resolution of N-protected 3-arylsulfonyl-7-aza-2-bromobicyclo[2.2.1]hepta-2,5-dienes promoted by (R,R)-hydrobenzoin is described, representing a new tool to fix the absolute stereochemistry of the 7-azabicyclo[2.2.1] skeleton.     

Reactions involving transition metals: XX. A comparison of the reactions of 1,2,3,4,7,7-hexafluorobicyclo[2.2.1]heptadiene,and 2,3-bis(trimethyltin)- and 2,3-dichloro-1,4,5,6,7,7-hexafluorobicyclo[2.2.1]hepta-2,5-dienes with low valent transition metal complexes

1,2,3,4,7,7-Hexafluorobicyclo[2.2.1]heptadiene (1) and 2,3-bis(trimethyltin)-1,4,5,6,7,7-hexafluorobicyclo[2.2.1]hepta-2,5-diene (2) react with [M(Ph₃P)₄] (M = Pt, Pd) to afford air-stable adducts. 2,3-Dichloro-1,4,5,6,7,7-hexafluorobicyclo[2.2.1]hepta-2,5-diene (3) gives only [PtCl₂(PPh₃)₂] with [Pt(Ph₃P)₄], but a low yield of an adduct was obtained with [Pd(PPh₃)₄]. The diene 1 also reacts with Fe(CO)₅ to form the complex [(C₇H₂F₆)Fe(CO)₄], and with [Rh(C₂H₄)₂(acac)] to give [(C₇H₂F₆)Rh(acac)] in which the diene acts as a bidentate ligand. Similar products could not be isolated from the reactions of 2 and 3. A stable adduct, believed to be [{C₇F₆(SnMe₃)₂}Rh(CO)₂(μ-Cl)₂Rh(CO)₂] has been isolated from the reaction between 2 and [Rh(CO)₂Cl]₂. This adduct reacts with PPh₃ to give the bridge-cleavage product [{C₇F₆(SnMe₃)₂}RhCl(CO)(PPh₃)₂]. Reaction of 1 with [Rh(CO)₂Cl]₂ gives an unstable adduct which could not be isolated, and 2 does not react at room temperature. The chloro derivative 3 reacts with [PdCl₂(PhCN)₂] to give the adduct [(C₇F₆Cl₂)PdCl(PhCN)], but 1 and 2 do not react under similar conditions. Stable substitution products [(C₇F₆R₂)M] (R = H, M = Fe(CO)₂(η-C₅H₅); R = SnMe₃, M = Fe(CO)₂(η-C₅H₅), Mn(CO)₅, Ir(CO)₂(PPh₃)₂, Rh(CO)₂(PPh₃)₂; R = Cl, M = Ir(CO)₂(PPh₃)₂, Rh(CO)₂(PPh₃)₂) have been isolated from the reactions of the dienes with carbonylmetal anions. Insertion of the CHCH bond occurs when 1 is heated with [MnMe(CO)₅] to give [{C₇F₆H₂C($\text{O)Me}M}$n(CO)₄], and this, on reaction with either PPh₃ or [Pt(PPh₃)₄], gives [(C₇F₆H₂COMe)Mn(CO)₄PPh₃].     

Cyclodimerization of bicyclo[2.2.1]hepta-2,5-diene in the presence of rhodium-containing zeolite catalysts

It has been shown that norbornadiene is dimerized in the presence of rhodium-containing zeolite catalysts, forming hexacyclic [4+2]dimers preferentially. The effect of the structure and the method of preparation and pretreatment of the catalysts on their activity and selectivity in norbornadiene cycloaddition was studied. The influence of the above parameters on the change in the electronic state of rhodium in the course of the reaction was also investigated.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1913–1919, November, 1994.     

Relative reactivities of bicyclo[3.2.1]octa-2,3-diene and 1,2-cycloheptadiene with conjugated dienes and styrene

Bicyclo[3.2.1]octa-2,3-diene (2) and 1,2-cycloheptadiene (3), generated by treatment of the corresponding dichlorides 4 and 5 with magnesium, were found to undergo cycloaddition reactions with 2,3-dimethylbutadiene, styrene, and 1,3-cyclopentadiene. 2, but not 3, was also found to undergo a (2 + 2) cycloaddition reaction with cis-pentadiene. The relative reactivities of 2 and 3 with cis-pentadiene, 2,3-dimethylbutadiene, styrene, and 1,3-cyclopentadiene at 60° in THF were found to be: 0·18, —; 1·0, 1·0; 0·60, 7·5; and 4·0, 150.     

Preparation of bicyclo[2.2.1]hepta-2,5-diene by the condensation of cyclopentadiene with acetylene

Summary The condensation of cyclopentadiene with acetylene under pressure gave a 40–45% yield of bicyclo[2.2.1]hepta-2.5-diene, the starting material for the synthesis of the insecticide aldrin.     

Reaction of bicyclo[2.2.1]hepta-2,5-diene with the arenesulfenamide—phosphorus(v) oxohalide system: chemo-, regio-, and steroselectivity

The chemo-, regio- and stereoselectivities of electrophilic sulfenylation of bicyclo[2.2.1]hepta-2,5-diene with arenesulfenamides activated by phosphorus(v) oxohalides were studied. The ratio of the products of endo- to exo-attack of the diene by the electrophilic species depends on the solvent nature. The proportions of the products formed upon addition to one double bond and upon homoallylic participation of the second double bond depend on solvent polarity, the nature of the halogen, the substituents in the sulfenamide benzene ring, and on the reaction time. In addition, the formation of mixed adducts was proven for the reaction carried out in acetonitrile and the formation of disulfenylation products was found in the reaction with excess sulfenylating reagent. Isomerization of exo-3-arylthio-endo-2-halobicyclo[2.2.1]hept-5-enes to the products formed with homoallylic participation of the second double bond, exo-5-arylthio-endo-3-halotricyclo[2.2.1.0^2,6]heptanes, was shown to be possible.     

Synthesis of 2,5-bis(piperidinomethyl)piperidine and 1,5-bis(aminomethyl)-3-azabicyclo[3.2.1]octanones

Schmidt reaction of mono- and bis-Mannich bases1 and2 c derived from cyclopentanone gave the corresponding basically substituted 2-piperidones3 and4, respectively. Reduction of the latter afforded5. DoubleMannich reaction of2 a–c with primary amines gave 3-azabicyclo[3.2.1]octanone derivatives6 a–e and7. The transamination of2 a was investigated.     

Die isomeren bicyclo[4.2.1]nonen-(3)-ole-(2)und bicyclo[4.2.1]-nonanole-(2)1

The preparation of exo and endo bicyclo[4.2.1]nonen-(3)-ol-(2) (3) and (4), and the preparation of exo and endo bicyclo[4.2.1]nonanol-(2) (1) and (2) from 3,3-dihalotricyclo[4.2.1.0^2,4]nonyl derivatives is described. On the basis of the configuration of the allylic alkohols 3 and 4 the configuration of the saturated compounds 1 and 2 has been unequivocally determined.     

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.     

Die isomeren bicyclo[4.2.1]nonen-(2)-ole-(4) und bicyclo[4.2.1]nonanole-(3)1

The preparation of exo and endo bicyclo[4.2.1]nonen-(2)-ol-(4) (3) and (4), and the preparation of exo and endo bicyclo[4.2.1]nonanol-(3) (1) and (2) from 3,3-dihalotricyclo[4.2.1.0^2,4]nonenyl derivatives is described. On the basis of the configuration of the allylic alkohols 3 and 4 the configuration of the saturated compounds 1 and 2 has been unequivocally determined.     

Enantioselective synthesis of (1R,2S,4S)-7-oxabicyclo[2.2.1]heptan-2-exo-carboxylic acid

A scalable enantioselective access to (1R,2S,4S)-7-oxabicyclo[2.2.1]heptan-2-exo-carboxylic acid 7, a key precursor in the synthesis of A2a receptor antagonist 1 by means of an enzymatic resolution of the respective butyl ester with lipase A from Candida antarctica, is described.     

Unusual reactivity of bicyclo[2.2.1]heptene derivatives during the ozonolysis

This paper describes mechanistic studies on the ozonolysis of bicyclo[2.2.1]heptene derivatives 6 and 7 obtained from (R)-(+)-pulegone through the cyclopentadiene 5 and its Diels-Alder reaction with maleic anhydride. The ozonolysis of the tricyclic diol 7 led to the ketone 8 with the same skeleton while the anhydride 6 gave rise to the epoxide 10 and the bis-lactone 11. The structure of 8, 10 and 11 are confirmed by X-ray analysis. These unexpected results are discussed in terms of a π complex between ozone and the double bond.     

Ruthenium-catalyzed homo Diels-Alder [2 + 2 + 2] cycloadditions of alkynyl phosphonates with bicyclo[2.2.1]hepta-2,5-diene

Ruthenium-catalyzed homo Diels-Alder [2 + 2 + 2] cycloadditions between alkynyl phosphonates and bicyclo[2.2.1]hepta-2,5-diene were studied. The observed reactivity was found to be dependent on the presence of the phosphonate moiety. The Ru-catalyzed cycloaddition was compatible with a variety of aromatic and aliphatic substituted alkynyl phosphonates, providing the corresponding phosphonate substituted deltacyclenes in low to good yields (up to 88%).     

Die stereoisomeren bicyclo[4.2.0]octan-cis-Diole-(7,8)

The stereochemical assignment of the bicyclo[4.2.0]octane-cis-7,8-diols is reinvestigated. It is shown that the cis-diols prepared by different routes are indeed stereoisomers, the lower melting being the exo-isomer (1), the higher melting the endo-isomer (2). The synthesis of the previously unknown trans-fused bicyclo[4.2.0]octane-cis-7,8-diol (3) via photosensitized cycloaddition of vinylene carbonate to cyclohexene is described.