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.     

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.     

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.     

Synthesis and Crystal Structure of 2-(Diphenylphosphine oxide)-3-(diphenylphosphine oxide ethynyl) spiro [bicyclo[2.2.1]hepta-2,5-diene-7,1''''-cyclopropane]

1 INTRODUCTION Organic phosphine compounds always attract great interest for their unique properties and extensive uses in biochemistry, pesticide chemistry and synthetic organic chemistry. In the last two decades, much attention has been paid to phosphorus-containing olefin and acetylenic compounds for their applications in transition metal chemistry, asymmetric catalysis and photorearrang- ement [1~7 ]. Previously, we have reported the crystal structure of a novel host compound which …     

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.     

Deprotonated 2,3:5,6-Dibenzo-7- aza bicyclo[2.2.1]hepta-2,5-diene as a Nitrido Nitrogen Source by Anthracene Elimination: Synthesis of an Iodide(nitride)chromium(VI) Complex

Instead of azides, which can be explosive and poorly soluble in nonpolar solvents, azabicycloheptadienes can be used to synthesize nitrides. The reaction of diiodide 1 with the lithium amide 3 provides the red nitride 2 in 60 % yield with loss of lithium iodide and anthracene. The remaining iodo ligand in 2 can undergo an exchange reaction with lithium amide 3 , but no more anthracene is released.     

Syntheses and tandem Diels-Alder reactivities of 7,7-diphenyl-[2.2.1]hericene (= 7-(diphenylmethylidene)-2,3,5,6- tetramethylidenebicyclo[2.2.1]heptane) and 7-oxa[2.2.1]hericene ( = 2,3,5,6-tetramethylidenebicyclo[2.2.1]heptan-7-one)

Syntheses of 7,7-diphenyl[2.2.1]hericene ( 4 ) and 7-oxa[2.2.1]hericene ( 5 ) are presented. Rate constants k₁ and k₂ of the two successive Diels-Alder additions of ethylenetetracarbonitrile (TCE) to 4 and to 5 have been evaluated. At 25° in toluene, the rate-constant ratio k₁/k₂ = 260 and 21 for 4 and 5 , respectively. These results are compared with those reported for the tandem Diels-Alder reactivity of 2,3,5,6-tetramethylidenebicyclo[2.2.1]heptane and other derivatives.     

Transition metal-catalyzed [4 + 2 + 2] cycloadditions of bicyclo[2.2.1]hepta-2,5-dienes (norbornadienes) and bicyclo[2.2.2]octa-2,5-dienes

The transition-metal-catalyzed [4 + 2 + 2] cycloadditions of norbornadienes, bicyclo[2.2.2]octa-2,5-diene, and benzobarrelene with 1,3-butadienes proceed in excellent yields using cobalt-based catalytic systems. Two key distinctions between these [4 + 2 + 2] cycloadditions and the corresponding transition-metal-catalyzed [2 + 2 +2] reactions of norbornadiene are the requirement of a bimetal catalytic system with a bisphosphine ligand for the former and exclusive regioselectivity in the [4 + 2 + 2] reaction of 2-substituted norbornadienes to produce 1-substituted adducts. These distinctions may indicate two distinct mechanisms for the [4 + 2 + 2] and [2 + 2 + 2] reactions.