7-Selenabicyclo[2.2.1]heptane

Thermolysis of a benzene solution of N-[4-(p-(methoxybenzyl)seleno)cyclohexanoyl]-N,S-dimethyldithiocarbonate affords the hitherto unknown 7-selenabicyclo[2.2.1]heptane in 48% conversion and in 20% yield after chromatography. G3(MP2)-RAD calculations predict a rate constant of 5 × 10(4) s(-1) at 80 °C (3.8 × 10(6) s(-1) at 200 °C) for the intramolecular homolytic substitution process involved in this cyclization.     

Conversion of bicyclo[2.1.0]pentane into 2,3-dioxabicyclo[2.2.1]heptane via t-butyl peroxymercuriation

Bicyclo[2.1.0]pentane has been converted in 45% yield into 2,3-dioxabicyclo-[2.2.1]heptane by the sequence t-butyl peroxymercuriation, iododemercuriation, epimerisation of the resultant 1-t-butylperoxy-3-iodocyclopentane, and reaction of the trans isomer with silver trifluoroacetate.     

Derivatives of exo-5-Aminomethyl-endo-5-methylbicyclo[2.2.1]hept-2-ene and exo-5-Aminomethyl-endo-5-methyl-exo-2,3-epoxybicyclo[2.2.1]heptane

exo-5-Aminomethyl-endo-5-methylbicyclo[2.2.1]hept-2-ene and its 2,3-epoxy derivative were synthesized, and their geometric parameters and conformational properties, in particular the barriers to rotation of the aminomethyl fragment about the exocyclic C⁵ÄC bond, were studied by the molecular-mechanics method (MMX) and compared with those found for structurally related exo-5-aminomethylbicyclo[2.2.1]hept-2-ene. The title compounds were brought into reactions with electrophilic reagents: arenesulfonyl chlorides, isocyanates, and isothiocyanates.     

1‐Phosphabicyclo[2.2.1]heptane

1‐Phosphabicyclo[2.2.1]heptanes Exo‐endo‐ and exo‐exo‐2.6‐dimethyl‐1‐phosphabicyclo [2.2.1]heptane have been obtained by cyclization of 2‐methyl‐4‐(2‐propenyl)phospholane in the presence of the complex base, sodium salt of diethylenglycolmonoethylether ‐ sodium amide in THF (NAMEDEG). The bicyclic phosphanes are characterized by reac‐tions with selenium, sulfur, (CH₃)₂SeO, CH₃I and HSO₃F, respectively, elemental analysis, X‐ray crystal structure analysis as well as ¹H, ¹³C, ³¹P NMR spectral measurements. The steric demand of these phosphanes as complex ligands has been estimated from the P, H coupling constants of the phosphonium fluorosulphates according to the Tolman model. The phosphane selenides were found to display the lowest values for the ¹J(Se, P) coupling constant, found up to now for alicyclic and cyclic aliphatic tertiary phosphane selenides. The ⁿJ(P, H)‐ and ⁿJ(H, H)_{n=2, 3} coupling constants have been extracted from the proton spectra at 600 MHz by computerized analysis.     

The electronic structure of bicyclo [2.2.1] heptane and of bicyclo [2.2.2] octane

An ab initia SCF-LCAO-MO study of bicyclo [2.2.1] heptane(I) and of bicyclo [2.2.2] octane(II) has been performed. The electronic structure and the nature of the molecular orbitals and of the bonds have been analyzed. Interactions between fragment orbitals may be recognized. The bridgehead C-H bonds interact dominantly “through-space” in I and “through-bond” in II. Some relations between electronic structure and molecular properties are discussed.     

Preparation of 1,2exo- and 1,2endo-Diiodo-bicyclo[2.2.1]heptane

1,2 exo-Diiodo-norbornane ( 4 ) was prepared from norcamphor hydrazone by oxidative iodination and subsequent rearrangement of the 2,2-diiodo-bicyclo [2.2.1]heptane ( 2 ). The stable α-iodohydrazone 11 was obtained from 1-iodo-bicyclo[2.2.1]heptan-2-one ( 10 ), which itself was prepared from 1-iodo-norbornene ( 5 ). Subsequent treatment of 11 with iodine lead to 1,2,2-triiodo-norbornane ( 12 ) and l,2-diiodo-norborn-2-ene ( 13 ). 1,2 endo-Diiodo-norbornane ( 14 ) was obtained by stereoselective reduction of 12 with tribtityltinhydride or by reaction of 13 with diimide.     

Carbon-13 n.m.r. spectra of 2,3-dimethylenebicyclo[2.2.1]heptanes and 2,3-dimethylene-7-oxabicyclo[2.2.1]heptanes

The ¹³C n.m.r. spectra of 11 derivatives of 2,3-dimethylenenorbornane, 1–11, of 5 derivatives of 2,3-dimethylene-7-oxanorbornane, 12–16, and of 2,3,5,6-tetramethylene-7-oxanorbornane (17) have been measured and the chemical shifts have been assigned. The effects of 1-methyl, 5-hydroxy, 5-acetoxy, 5-para-bromobenzenesulphonyloxy and 5-keto substituents on the olefinic carbons of the s-cis-butadiene group are compared with the same substituent effects reported for model compounds. Apparent linear correlations between the reciprocals of the V←N transition energies of the butadiene chromophores and the differences of the chemical shifts ΔδC between the quaternary and methylene olefinic carbons are found for the dienes 1–3, 12–14, butadiene and 2,3-dimethylbutadiene. The ΔδC of the olefinic carbons of the tetraene 17 also falls on the correlation line if the average of the two absorption hands at 250 and 228 nm is taken for the V←N transition energy of this compound. The chemical shift of the carbon of the methano bridge H₂C-7 is almost insensitive to the presence of one or two methylene groups at C-2,3, in contrast with the downfield shift of 10–14 ppm observed when an endocyclic double bond is introduced into the norbornane skeleton.     

Poly-2,3- and 2,7-Bicyclo[2.2.1]hept-2-enes: Preparation and Structures of Polynorbornenes

The polymerization of norbornene in the presence of either radical catalysts having a short half-life at the polymerization temperature or ethylaluminum dichloride yields a saturated polymer having a rearranged structure with 2,7 linkages. Polymerization in the presence of either Pd(C₆H₅CN)₂Cl₂ or Ziegler-Natta catalysts containing TiCI₄ and A1R₃ or R₂ A1C1 yields a saturated polymer with 2,3 linkages.     

Thermal decomposition of 7-isopropylidene-2,3-dioxabicyclo[2.2.1]heptane: Evidence for allene oxide and cyclopropanone intermediates

The saturated endoperoxide derived from 6,6-dimethylfulvene was shown to be a unique source of an allene oxide and a cyclopropanone: inter- and intramolecular trapping experiments provided permissive evidence that such intermediates are indeed operative in the thermal isomerizations of fulvene endoperoxides.     

Chiral 7-Oxabicyclo[2.2.1]heptane Building Blocks for Prostanoids

Russian Journal of Organic Chemistry - Methyl (Z)-3-[(2R,3R,4S,5S)-5-(2-methoxy-2-oxoethyl)-3,4-(isopropylidenedioxy)tetrahydrofuran-2-yl]-prop-2-enoate was synthesized, and its intramolecular...     

Intramolecular hydrogen abstraction reaction promoted by alkoxy radicals in carbohydrates. Synthesis of chiral 2,7-dioxabicyclo[2.2.1]heptane and 6,8-dioxabicyclo[3.2.1]octane ring systems

The reaction of specifically protected anhydroalditols with (diacetoxyiodo)benzene or iodosylbenzene and iodine is a mild and selective procedure for the synthesis of chiral 6,8-dioxabicyclo[3.2.1]octane and 2,7-dioxabicyclo[2.2.1]heptane ring systems under neutral conditions. This reaction can be considered to be an intramolecular glycosidation that goes through an intramolecular hydrogen abstraction promoted by an alkoxy radical followed by oxidation of the transient C-radical intermediate to an oxycarbenium ion. This methodology is useful not only for the preparation of chiral synthons but also for the selective oxidation of specific carbons of the carbohydrate skeleton, constituting a good procedure for the synthesis of protected uloses.     

7-oxabicyclo[2.2.1]heptane hydrochloride and hydrofluoride: Quantum-chemical investigation

Structural parameters, IR spectra and energy of H-bonds for binary complexes of 7-oxabicyclo[2.2.1]heptane molecule with molecules of HCl and HF are calculated by quantum-chemical B3LYP/cc-pVTZ method with inclusion to the basis of diffuse “aug”-orbitals of halogen, oxygen and bridgehead hydrogen.     

Bicyclo[2.2.1]heptane derivatives containing two vicinal CFC1 groups. The tendency tocis-dehalogenation

Dehalogenation ofexo-cis-2,3-dichloro-2,3-difIuoro-1,2,3,4,4a,-5,8,8a-octahydro-l,4,5,8-dimethanonaphtalene yields 2,3-difluoro-l,4,4a,5,8,8a-hexahydro-1,4,5,8-dimethanonaphthalene as the sole product, whereas the isomerictrans-dichloride affords a mixture of the above product with 2-chloro-3-fluoro-l,4,4a,5,8,8a-hexahydro-l,4,5,8-dimethanonaphthalene (2 1 respectively).Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 411–413, February, 1993.     

Carbon-13 chemical shifts of bicyclo[3.2.1]octane and bicyclo[2.2.1]heptane derivatives

¹³C chemical shifts of more than fifty bicyclo[3.2.1]octane and bicyclo[2.2.1]heptane derivatives (hydrocarbons, alcohols, ketones and esters) have been determined. The usefulness of ethyl derivatives for the assignment of close ¹³C chemical shifts in bicyclic methyl derivatives is shown both for the bicyclo[3.2.1]octane and bicyclo[2.2.1]heptane series. Comparison of substituent effects on α-, β-, γ- and δ-carbons in both series of compounds shows remarkable differences in steric interactions. In contrast to the rigid bicyclo[2.2.1]heptane system, both chair and boat conformations can be predominant in the bicyclo[3.2.1]octane series with the conformationally flexible 6-membered ring.     

Synthesis of opioid ligands having oxabicyclo[2.2.2]octane and oxabicyclo[2.2.1]heptane skeletons

Two types of novel skeletons were synthesized from morphinan and 4,5-epoxymorphinan derivatives by using stable and unstable sulfur ylide.     

Enzymatic preparation of optically active 7-oxabicyclo[2.2.1] heptane derivatives

Enzymatic resolution of endo-7-oxabicyclo [2.2.1] hept-2-yl butyrates 3 and 5 using lipase from Candida cylindracea led to optically pure bicyclic alcohols and esters being important intermediates for the synthesis of biologically active compounds.