Low-Temperature Polymerization of endo- and exo-2-Methyl-7-oxabicyclo-[2.2.1]-heptane

Abstract

Polymerization of the title compounds in methylene di-chloride with PF, catalyst have shown that the rate of polymer formation drops sharply with temperature and the polymerization ceases entirely around -60 to -70°C. Ex-periments carried out with the exo-2-Me isomer have shown that at -30°C a limiting conversion of approx 40% is attained and simultaneously the molecular weight and the molecular weight distribution level off. At -50°C the same limiting conversion level is reached; however, the molecular weight level is higher and a study of changes in molecular weight distribution with time indicates that at this tempera-ture a greater proportion of chains remain active throughout the polymerization. Even at -30°C, however, experiments with changing conditions, especially the temperature, during the runs have demonstrated that the systems are not “dead” after the limiting conversion has been reached. Polymeriza-tion of the endo-2-Me isomer at -50°C has shown that in the time interval studied the limiting viscosity number increases essentially linearly with time.     

Polymerisation von cis- und trans-8-Oxabicyclo[4.3.0]nonan

Ohne Zusammenfassung     

Substituierte 9-Oxabicyclo[4.2.1]- und 9-Oxabicyclo[3.3.1]nonane IV. endo,endo-2,5-Dihydroxy-9-oxabicyclo[4.2.1]nonan,endo, endo-, endo,exo- und exo,exo-2,6-Dihydroxy sowie endo,exo-2,7-Dihydroxy-9-oxabicyclo[3.3.1]nonan; Darstellung und Umwandlungsprodukte

The synthesis of the following compounds and reaction products thereof are described: endo, endo-2,5-dihydroxy-9-oxabicyclo[4.2.1]nonane ( 3–5 ), epimeric 2,6-dihydroxy-9-oxabicyclo[3.3.1]nonanes (endo, endo: 6–8 , exo, exo: 29–32 , and endo, exo: 43–45 ), and endo, exo 2,7-dihydroxy-9-oxabicyclo[3.3.1]nonane ( 46–50 ).     

Die säurekatalysierte Isomerisierung von 7-Oxabicyclo[2.2.1]-heptadien- und Oxepin-Derivaten [1]

The acid catalyzed isomerization of several substituted oxanorbornadienes 4 and oxepines 10 - easily available from 4 by a photochemical and a consecutive thermal step - allows the synthesis of several highly substituted phenols and 2,4-cyclohexadienones in a straightforward manner and with good to excellent yields. The formation of the methoxycarbonyl-hexadienes 18e and 18f upon photolysis of 9e and 17f in methanol supports the structure elucidation. The relative importance of the McLAFFERTY and EMERY effects in the mass spectral degradation of methoxycarbonyl and methyl substituted phenols are discussed.     

Synthesis and stereochemical assignment of exo- and endo-7-methyl-7-azabicyclo[2.2.1]heptan-2-ol

[formula: see text] The syntheses of both exo and endo stereoisomers of 7-methyl-7-azabicyclo[2.2.1]heptan-2-ol were achieved in straightforward fashion. Alternatively, the intramolecular cyclization of syn-4-N-methylaminocyclohexane 1,2-epoxide was found to give exo-7-methyl-7-azabicyclo-[2.2.1]heptan-2-ol as the sole product. The stereochemistry of the exo isomer was unequivocally confirmed by X-ray crystallography.     

Die Solvolyse von exo- und endo-3-Chlor-bicyclo[3.2.1]octan

The rates of solvolysis of exo and endo 3-chloro bicyclo[3.2.1]octane 1a and 2a have been measured in 80 vol.% aqueous ethanol. The axial endo chloride reacts 263 times as fast as the equatorial exo epimer. This remarkably large rate difference is ascribed to sterically accelerated ionisation of the axial endo epimer due to the ethano bridge.     

Synthese von endo- und exo-1,3-Dimethyl-2,9-dioxa-bicyclo[3.3.1]nonan

Synthesis of endo- and exo-1,3-dimethyl-2,9-dioxabicyclo[3.3.1]nonane The synthesis of a host-specific substance in norway spruce infested by Trypodendron lineatum OLIV . is described (cf. scheme 1 and 2). Alkylation of the acetyl-acetone di-anion (II) with 3-methyl-3-buten-1-yl-bromide (I) followed by sodium boro-hydride reduction yields erythro- and threo-8-methyl-8-nonen-2,4-diol (IV and V) which are separated by chromatography. Their configurations were established by converting them under equilibrium conditions into one (VI) or two (VII and VIII) benzal derivatives. Oxidative cleavage with ozone of the terminal double bond in the erythro diol IV produces a dihydroxy ketone IX which spontaneously cyclizes to endo-1,3-dimethyl-2,9-dioxa-bicyclo[3.3.1]nonane (X). The threo diol V is converted by the same reaction sequence exclusively into exo-1,3-dimethyl-2,9-dioxa-bicyclo-[3.3.1]nonane (XII). Comparison of the NMR. data of the two acetals X and XII with that of the natural product establishes the endo configuration of the latter. A second, more convenient, synthesis of a mixture of the acetals X and XII starting from the bromo-acetal XIII is also reported.     

Substituierte 9-Oxabicyclo[4.2.1]- und 9-Oxabicyclo[3.3.1]nonane III. neue ergiebige synthese von 2, 7-dioxatwistan und endo-2-hydroxy-9-oxabicyclo[3.3.1]nonen-(6)

Iodine cleavage of the [3.3.1]-iodomercuri compound 4 , easily prepared from cis, cis-cyclooctadiene-(1,5) by oxymercuration of the monoepoxide 1 (→ 3 ) followed by treatment with potassium iodide, leads to three isomeric iodides 6, 7 , and 8 , the [3.3.1]-exo-iodo isomer 8 being the predominant product. Intramolecular substitution in 8 opens an attractive new route to unsubstituted 2,7-dioxatwistane ( 19 ) [2], whereas dehydrohalogenation of 7 and 8 yields the unsaturated alcohol 17 [2], a suitable starting material for the preparation of substituted 2,7-dioxatwistanes [2], 2,7-dioxaisotwistanes ( e ) [2], and 2,8-dioxa-homotwistbrendanes ( f ).     

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...     

Derivatives of 7-Oxabicyclo[2.2.1 ]hept-5-ene and 7-Oxabicyclo[2.2.1 ] heptane. Synthesis,transformations, and stereochemistry using nmr methods

Synthesis and stereochemistry of various endo-2- and exo-2-substituted-7-oxabicyclo[2.2.1]-hept-5-enes and -heptanes are described. The nmr spectra of several derivatives are reported and discussed. Use is made of this data to allow determination of the stereochemical integrity of the system. Facile chromatographic separation methods were found for endo- and exo-2-sub-stituted-7-oxabicyclo[2.2.1 ]hept-5-enes and -heptanes.     

Regioselective Radical Additions to 7-Oxabicyclo[2.2.1]hept-5-en-2-one

Radical addition to 7-oxabicylco[2.2.1]hept-5-en-2-one ( 1 ) was examined from a regiochemical point of view, and despite the small electronic anisotropy of the double bond, electrophilic radicals were found to add preferentially at C(5) with selectivities of up to 5:1. We also report the first case of an inversion of the regioselectivity of a radical reaction using Lewis acids.     

A Convenient Synthesis of Some 1,4-Disubstituted 7-Oxabicyclo[2.2.1]heptanes

An efficient synthesis of a 1,4-disubstituted 7-oxabicyclo[2.2.1]heptane intermediate and its subsequent conversion to a potential PAF antagonist is described.     

The Preparation of Optically Pure 7-Oxabicyclo [2.2.1]hept-2-ene Derivatives. The CD Spectrum of (+)-(1R)-7-Oxabicyclo [2.2.1]hept-5-en-2-one

(?)-1-Camphanoyloxyacrylonitrile (=(?)-1-cyanovinyl camphanate; 1 ) obtained from the commercially available (?)-camphanoyl chloride and 2-oxo-propiononitrile added to furan at 20° in the presence of Cu (BF₄)₂ · 6H₂O or ZnI₂ and gave a mixture of 2-cyano-7-oxabicyclo [2.2.1]hept-5-en-2-yl camphanates ( 2–5 ) from which isomer 5 could be obtained pure by crystallization. The latter was transformed into (+)-(1R)-7-oxabicyclo[2.2.1]hept-5-en-2-one ( 6 ) in high yield and optical purity. Adducts 2–4 were recycled into 1 +furan by heating in toluene, and (?)-camphanic acid was recovered after saponification of 5 . The absolute configuration of 6 was deduced from its CD spectrum which showed two 1200-cm_?1 Franck-Condon series for its n→π transition.     

Asymmetric synthesis of 3,4-diaminocyclohexanol and endo-7-azabicyclo[2.2.1]heptan-2-amine

Hydroboration of (1R,2R)-bis[(S)-1-phenylethylamino]cyclohex-4-ene and its derivatives with several borane reagents gave diastereomeric mixtures of the 3,4-diaminocyclohexanol derivatives. Cyclization of the prevalent diastereomer with the R configuration of the newly formed stereocenter under Mitsunobu conditions, followed by reductive removal of the N-substituents, gave the optically pure endo-7-azabicyclo[2.2.1]heptane-2-amine.     

Azabrendanes V. Synthesis and reactions of stereoisomeric exo- and endo-5-aminomethylbicyclo[2.2.1]hept-2-ene-based ureas

A number of stereoisomeric ureas (N-[aryl(benzyl, or cycloalkyl)carbamoyl]-exo(endo)-5-aminomethylbicyclo[2.2.1]hept-2-enes) have been synthesized from bicyclo[2.2.1]hept-2-en-exo(endo)-5-carbonitrile by reduction with lithium aluminum hydride and subsequent reaction of the resulting amines with aryl (benzyl, or cycloalkyl) isocyanates. Regioselective alkylation of stereoisomeric ureas has been performed with benzyl chloride under liquid/solid phase-transfer catalysis. The outcome of the reactions of ureas with peroxy acids is dependent upon the orientation of substituents in the bicyclic fragment. Exo-isomeric ureas are transformed into corresponding epoxy-derivatives, while reactions of the endo-isomers are accompanied by intramolecular cyclization, resulting in the formation of azatricyclononane derivatives. Quantum-chemical calculations have established a decisive role for additional hydrogen bonding in the stabilization of transition states in these heterocyclization reactions of ureas. The structures and stereochemical homogeneity of the products have been confirmed by the analysis of ¹H and ¹³C NMR spectra and correlation spectroscopy. The mechanism of the intramolecular heterocyclization reaction of ureas and carboxamide of endo-5-aminomethyl-exo-2,3-epoxybicyclo[2.2.1]heptane series has been studied at the BHandHLYP/6-31G(d) level of theory.      

对映体纯1-甲基-7-氧杂双环[2.2.1]庚烷-2-酮的制备

1-甲基 - 7-氧杂双环 [2 .2 .1 ]庚烷 - 2 -酮 ( 1 )是萜类天然产物全合成中的重要中间体 ,能被广泛地应用于多种桉烷 ( Eudesmane)、沉香呋喃 ( Agarofuran)和降胡萝卜素 ( Norcarotenoids)等倍半萜天然产物的全合成[1,2 ] .我们以对映体纯化合物 1为原料 ,实现这类天然产物的不对称全合成 [3～ 6 ] .消旋的化合物 (± ) - 1可以 2 -甲基呋喃和 2 -氯丙烯腈为原料 ,经 3步反应得到 [2 ] .但对映体纯化合物 1的制备尚未见报道 .本文用化学拆分方法 ,成功地制备了对映体纯的 ( + ) - 1和 ( - ) - 1 ,并确定了其绝对构型 .1　结果与讨论为减…     

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.