The adamantane rearrangement of 1,2-trimethylenenorbornanes. Part IV. Hydride-ion abstraction in 1,2-exo-trimethylenenorbornane

In the AlBr₃-catalyzed adamantane rearrangement in CS₂ of 1,2-exo-trimethylenenorbornane ( 1 ) to 2-endo,6-endo-trimethylenenorbornane ( 3 ), hydride-ion abstraction occurs at C(6) from the exo-side. The k_H/k_D value for competition between 1 and 5 (D_exo-C(6)) was 1.58 ± 0.05, whereas no kinetic isotope effect was operative for competition between unlabeled 1 and 4 (D_endo-C(5)) and between 1 and 6 (D_endo-C(6)).     

The adamantane rearrangement of 1,2-trimethylenenorbornanes. Part V. Rearrangements of 1,2-trimethylenenorbornanes initiated by regioselective formation of carbocation centers at C(2) and C(6)

The behaviour of the regioselectively generated carbocation centers at C(2) and C(6) in 1,2-trimethylenenorbornanes was investigated in order to study the occurrence or absence of a degenerate rearrangement E⇄M in the adamantane rearrangement of both 1,2-endo- ( 1 ) and 1,2-exo-trimethylenenorbornane ( 2 ) to 2-endo,6-endo-trimethylenenorbornane ( 3 ). A degenerate rearrangement E⇄M is inevitably involved inasmuch as a 1,2-trimethylenenorborn-2-yl cation E not only is formed directly as manifested by the conversions of the reactants 4 (C(2), C(3)-olefin) and 6 (C(2), C(3′)-olefin), but also indirectly (via F→E ) if the leaving group at C(6) to be ionized occupies the endo-position (6-endo-alcohol 8 ). No degenerate rearrangement E⇄M is operative starting from reactants that lead directly to a 2,6-trimethylenenorborn-2-yl cation G ; this is the case with both the ionization of the 6-exo-alcohol 10 having the leaving OH-group in a stereoelectronically favoured configuration to undergo simultaneous C(1), C(2)-bond migration (→ G ) as well as the protonation of the olefin 13 which is followed by same reaction pathway.     

The Adamantane Rearrangement of 1,2endo-Trimethylenenorbornane. Preliminary communication

1,2endo-Trimethylenenorbornane (1) in the presence of aluminium bromide in carbon disulfide at ?60° isomerizes at a much higher rate than its 2exo-isomer 2 to 2endo, 6endo-trimethylenenorbornane (3) as the sole product. By consequence, the hydrocarbon 2 being the next intermediate in the sequence of the adamantane rearrangement of 1 seems to be very unlikely.     

Solvolysen von 4-Alkylidenbicyclo[3.2.0]hept-2-en-6-olen. Synthese von 1-Vinylfulvenen und 8,8-Diphenylheptafulven

Solvolysis of 4-Alkydenbicyclo[3.2.0]hept-2-en-6-oles. Synthesis of 1-Vinylfulvenes and 8,8-Diphenylheptafulvene Four 4-alkylidenebicyclo[3.2.0]hept-2-en-6-ones 2–5 , obtained via ketene cycloaddition to fulvenes, were reduced to separated mixtures of the ‘endo’ -alcohols ‘endo’- 6 to ‘endo’- 9 (68–73%) and ‘exo’- 6 to ‘exo’- 9 (3–20%). Treatment of some of these alcohols with (CF₃SO₂)₂O in CH₂Cl₂/pyridine caused a spontaneous solvolysis to yield unsaturated 7-membered rings as pyridinium triflates 10–12 or 1-vinylfulvenes 13 and 14 , a new class of reactive tetraenes: Both ‘endo’- 9 and ‘exo’- 9 , having two methyl groups at C(7), were converted into the vinylfulvene 13 (≈ 80%). The alcohols with two H-atoms at C(7) exhibited a stereochemically controlled reaction selectivity, inasmuch as ‘endo’- 6 to ‘endo’- 8 afforded only the corresponding 7-membered-ring pyridinium salts 10–12 (66–79%), while ‘exo’- 6 produced only the vinylfulvene 14 (77%). A stereoelectronic control argument explains the C(1), C(5)-bond cleavage with ‘endo’- B and ‘endo’– 6 -‘endo’- 8 , as well as the C(1), C(7)-bond cleavage with ‘exo’- B , ‘exo’- 6 , and with both ‘endo’- and ‘exo’- 9 . Thermolysis (120°) of the pyridinium triflates 10 and 11 yielded the 3-isopropenyl-cycloheptatrienes 18 and 19 , respectively (≈90%); similar conditions (145°) applied to the triflate 12 produced the doubly cyclized fluorene derivative 21 (60%). When the iodide 22 derived from the triflate 12 with Nal was heated in refluxing toluene, 8,8-diphenylheptafulvene ( 23 , 86%) was obtained.     

Stereochemical studies. 58. Saturated heterocycles. 39. Preparation and steric structures of dihydro-1,3-oxazines, 1,3-oxazin-2-ones and 1,3-oxazine-2-thiones fused with norbornane and norbornene

3-endo-Aminobicyclo[2.2.1]hept-5-ene-2-endo-carboxylic acid ( 1 ), prepared from endo-norborn-5-ene-2,3-dicarboxylic acid anhydride, and the analogous saturated cis-exo-amino acid ( 3 ) were reduced with lithium aluminum hydride to the aminoalcohols 2 and 4 ; the latter were cyclized by means of arylimino ethers to methylene-bridged tetrahydro- ( 6a-c ) and hexahydro-3,1-benzoxazines ( 7b-d ), respectively. The endo ( 2 ) and exo ( 4 ) aminoalcohols were converted to methylene-bridged tetrahydro-3,1-benzoxazin-2-one ( 9 ) and hexahydro-3,1-benzoxazin-2-one ( 12 ) with ethyl chloroformate and sodium methoxide; treatment of the alcohols with carbon disulfide gave, via the dithiocarbamates, the corresponding 2-thiones ( 11, 13 ). The structures were confirmed by ir and nmr spectroscopy.     

Stereoselectivity of the Diels-Alder Reaction of (E)-γ-Oxo-α,β-Unsaturated Thioesters with Cyclopentadiene

The stereoselectivity of the Diels-Alder reaction of (E)-γ-oxo-α,β-unsaturated thioesters 3a-3d with cyclopentadiene is greatly enhanced in the presence of Lewis acids favoring the endo acyl isomers 4a-4d . In the absence of Lewis acid, Diels-Alder reaction of 3a-3d with cyclopentadiene at 25 °C gave two adducts 4a-4d and 5a-5d in a ratio of 1:1 respectively. In the presence of Lewis acids, Diels-Alder reaction of 3a-3d with cyclopentadiene gave 4a-4d and 5a-5d in ratios of 75-94:25-6 respectively. The stereoelectivity was enhanced to ratios of 95-98:5-2 with lowering the reaction temperature. The stereochemistry of the cycloadducts 4 and 5 was confirmed by iodocyclization. Reaction of the endo-thioester 5c with I₂ in aqueous THF at 0 °C gave the novel methylthio group rearranged product 6c in 80% yield, the first example of iodo-lactonization of endo-thioesters. Reaction of the endo-acyl isomer 4b with I₂ under the same reaction conditions gave an isomeric mixture of 7b and 8b in 1:2 ratio. The stereochemistry of the thioester group in 8b was proved by X-ray single-crystal analysis. The solvent effect on the endo selectivity of (Z)-γ-oxo-α,β-unsaturated thioester 2b was also examined.     

A Further Synthetic Approach to the Adamantane Isomer 2, 5-Trimethylenenorbornane (Tricyclo [5.3.0.03,9]decane, 4-Homotwistbrendane)

A further synthetic approach to 2, 5-trimethylenenorbornane ( 1 ; tricycle [5.3.0.0^3,9]decane, 4-homotwistbrendane), a member of the «adamantaneland», is described starting from methyl 5-oxo-2endo-norbornanecarboxylate ( 5 ). The required C2-chain was introduced by a Wittig-Horner reaction and the ring closure of the trimethylene bridge achieved by an acyloin condensation.     

Additions to bicyclic olefins—X: Stereochemistry of the oxymercuration-demercuration of cis-bicyclo[3.3.0]oct-2-ene,endo-trimethylene-norborn-8-ene and related olefins

The stereochemistry of the oxymercuration-demercurarion (OM-DM) of olefins related to the cis-bicyclo(3.3.0]octane and endo-2,3-trimethylenenorboniane structures was determined. In the case of cis-bicyclo(3.3.0]oct-2-ene, hydration occurs preferentially at the less hindered 3-position, with little preference shown for exo vs endo. The more hindered 2-product shows a 11:1 preference for the exo-product. The presence of Me groups at positions 2- or 3-, results in the formation of the tertiary alcohols with approximately a 4:1 favoring of the exo-isomer. (The oxymercuration intermediate exhibits a rapid equilibration with time. Consequently, the 4:1 ratios may not represent the true limit for the isomer distribution in the initial kinetic product.) Similarly, 2-methylenebicyclo[3.3.0]octane reveals an 8:1 preferential formation of the exo-alcohol. In the case of endo-trimethylene-norborn-8-ene, the oxymercuration stage is extraordinarily slow and the results do not fit this pattern. Possibly the very slow oxymercuration stage permits equilibration of the initial reaction product. On the other hand, the reaction is fast with 8-methylene-endo-trimethylenenorbornane and the product is 100% of the tertiary exo-alcohol. The same behavior is observed for 2-methylenenorbornane. Surprisingly, 2-methylene-endo-trimethy-lenenorbornane fails to undergo oxymercuration. Consequently, both endo-trimethylenenorborn-8-ene and 2-methylene-endo-trimethylenenorbornane exhibit an exceptional inertness toward oxymercuration, presumably related to the highly rigid U-shaped structure of the parent system.     

Stereoselective Synthesis of 2,4,6-Trimethylcyclohex-4-ene-1,3-diol Derivatives and of polypropionate fragments with four contiguous stereogenic centers

The Diels-Alder adduct (±)- 3 of 2,4-dimethylfuran and 1-cyanovinyl acetate was converted stereoselectively into benzyl 6-(4-chlorophenylsulfonyl)-1,3-exo,5-trimethyl-7-oxabicyclo[2.2.1]hept-5-en-2-exo-yl ( 26 ) and -2-endo-yl ether ( 36 ). Addition of LiAlH₄ to the latter led to the 3-O-benzyl derivatives 28 and 37 of (1RS,2SR,3SR,6SR)- and (1RS,2SR,3RS,6SR)-5-(4-chlorophenylsulfonyl)-2,4,6-trimethylcyclohex-4-ene-1,3-diol, respectively. Methylenation of 6-exo-(4-chlorophenylthio)-1-methyl-5-methylidene-7-oxabicyclo[2.2.1]heptan-2-one ( 16 ), obtained by reaction of (±)- 3 with 4-Cl-C₆H₄SCl and saponification gave, 6-exo-(4-chlorophenylthio)-1-methyl-3,5-dimethylidene-7-oxabicyclo [2.2.1]heptan-2-one ( 43 ), the reduction of which with K-Selectride afforded 6-exo-(4-chlorophenylthio)-1,3-endo-dimethyl-5-methylidene-7-oxabicyclo[2.2.1]heptan-2-endo-ol ( 44 ). The 3-O-benzyl derivative 48 of (1RS,2RS,3RS,6SR)-5-(4-chlorophenylsulfonyl)- 2,4,6-trimethylcyclohex-4-ene-1,3-diol was derived from 44 via based-induced oxa-ring opening of benzyl 6-endo-(4-chlorophenylsulfonyl)-1,3-endo-5-endo-trimethyl-7-oxabicyclo[2.2.1]hept-2-endo-yl ether ( 49 ). Benzylation of 28 , followed by reductive desulfonylation and oxidative cleavage of the cyclohexene moiety afforded (2RS,3SR,4RS,5RS)-3,5-bis(benzyloxy)-2,4-dimethyl-6-oxoheptanal ( 32 ).     

Pd(II)-catalyzed vinylic polymerization of norbornene and copolymerization with norbornene and copolymerization with norbornene carboxylic acid esters

The vinylic polymerization of norbornene and its copolymerization with norbornene carboxylic acid methyl esters were investigated. Norbornene was polymerized by us using di-μ-chloro-bis-(6-methoxybicyclo[2.2.1]hept-2-ene-endo-5σ,2π)-palladium(II) as catalyst. The polymerization time can be decreased by a factor of 100000 by activation of the catalyst with methylaluminoxane (MAO). With this palladium catalyst activated by MAO, 140 t of norbornene can be polymerized per mol palladium per h. This catalyst system was much more active than [Pd(CH₃CN)₄](BF₄)₂ ( I ). The polymerization of norbornene by (6-methoxybicyclo[2.2.1]hept-2-ene-endo-5σ,2π)-palladium(II) tetrafluoroborate was also possible but it was not as fast as the polymerization by Pd catalysts activated with MAO. We were also able to obtain copolymers of norbornene and 5-norbornene-2-carboxylic acid methyl ester (exo/endo = 1/4 or 2/3) containing between 15 and 20 mol-% ester units. The copolymerization of norbornene and 2-methyl-5-norbornene-2-carboxylic acid methyl ester (exo/endo = 7/3) was faster than the copolymerization mentioned before. In contrast the homopolymerization of 2-methyl-5-norbornene-2-carboxylic acid methyl ester was 10 times slower than that of 5-norbornene-2-carboxylic acid methyl ester (exo/endo = 1/4).     

Stereochemische Aspekte der Addition von Ketenen an Cyclopentadien

Earlier work has shown that the cyclo-addition of a ketene to a conjugated diene is always (a) 2 + 2, (b) polarily directed, and (c) suprafacial with respect to the diene C?C. The adducts of ketenes and cyclopentadiene are thus always 7-substituted bicyclo [3.2.0] hept-2-ene-6-ones. New evidence is presented to show that unsymmetrically substituted ketenes add to cyclopentadiene in such a manner that the larger substituent has a greater tendency to take up the endo- position in the adduct. This is interpreted to mean that a ketene participates in such reactions antarafacially. Thus the ketene approaches cyclopentadiene (a) with its functional plane perpendicular to that of the ring, (b) with the carbonyl carbon over the middle of the ring, and (c) with the larger of the two substituents oriented preferentially away from the ring (transition state 11 ). This endo-specificity for the larger ketene substituent is demonstrated by the indicated endo/exo ratios observed in the cyclo-adducts from ketenes with the following substituent pairs: C₆H₅/H = >95/<5, CH₃/H = 98/2, Cl/H = 97/3, CH₃O/H = >95/<5, C₆H₅/CI = >95/<5, C₆H₅/CH₃ = >95/<5, CH₃/Cl = 80/20, CH₃/CH?CH₂ = ～65/35, C₂H₅/CH₃ = ～60/40, n-C₃H₇/CH₃ = ～60/40, CH₃/Br = 56/44. These ratios enable a list to be compiled indicating the endo-specificity of the ketene substituents. The order closely parallels the space filling capacity as derived by other methods. The establishment of such ratios required reliable configurational assignments at carbon 7. These were derived by five methods based upon the following effects: (1) Both H? C7 and CH₃? C7 cause nmr. signals at higher field in endo-position (compared with exo). (2) The CH₃? C7 group in exo-position gives rise to a nuclear Overhauser effect with the vicinal H? C1, and in one case also with the trans-annular H? C5. (3) The nmr.-coupling constants of H? C7-exo (observed at H? C7) with H? C1 is always larger than of H? C7-endo. (4) The coupling constant of H? C7-exo with H? C6 (known to be exo-) of the LiAlH₄ reduction products of the cyclo-adducts (observed at H? C6) is always larger than that of H? C7-endo. (5) The nmr. signals of most protons in the cyclo-adducts are at higher field in benzene than in chloroform solution; this “benzene shift” is larger for H? C7 or for CH₃? C7 when in exo- than when in endo-position.     

The Carbonyl Group as Homoconjugated Electron-Releasing Substituent. Regioselective electrophilic additions at bicyclo[2.2.1]hept-5-en-2-one,bicyclo[2.2.2]oct-5-en-2-one,and derivatives

In CHCl₃, CH₃CN, or AcOH, benzeneselenenyl chloride (PhSeCl), bromide (PhSeBr), and acetate (PhSeOAc), 2-nitrobenzenesulfenyl chloride (NO₂C₆H₄SCl), and 2,4-dinitrobenzenesulfenyl chloride ((NO₂)₂C₆H₃SCl) added to bicyclo[2.2.1]hept-5-en-2-one ( 5 ) in an. anti fashion with complete stereo- and regioselectivity, giving adducts 20–24 in which the chloride, bromide, or acetoxy substituent (X) occupies the endo position at C(6) and the Se- or S-substituent (E) the exo position at C(5), The addition 5 + (NO₂)₂C₆H₃SCl→ 24 was accompanied by the formation of (1RS, 2RS)-2-(2,4-dinitrophenylthio)cyclopent-3-ene-l-acetic acid ( 25 ). The latter was the major product in AcOH containing LiClO₄. The additions of PhSeCl and PhSeBr to bicyclo[2.2.2]oct-5-en-2-one ( 6 ) were less stereoselective (proportion of exo vs. endo mode of electrophilic attack was ca. 3:1) but highly regioselective gazing adducts 27/28 and 29/30 , respectively, the regioselectivity being the same as that of the electrophilic additions of 5 . The reaction of PhSeCl with a 4:1 mixture of 2-exo-chloro- and 2-endo-chlorobicyclo[2.2.1]hept-5-ene-2-carbonitriles ( 12 ) was slower than addition 5 + PhSeCl; it gave adducts 31/32 (4:1) in which the PhSe moiety occupies the exo position at C(6) and the Cl atom the endo position at C(5). The addition of PhSeCl to 2-chlorobicyclo[2.2.1]oct-5-ene-2-carbonitriles ( 13 ) was very slow and gave adducts with the same regioselectivity as 12 + PhSeCl, but opposite with that of reactions of the corresponding enones 5 and 6 . PhSeX (X = Cl, Br, OAc) added to 2-cyanobicyclo[2.2.1]hept-5-en-2-yl acetates ( 14 ) with the same regioselectivity as 12 + PhSeCl. The additions of PhSeCl, PhSeBr, NO₂C₆H₄SCl, and (NO₂)₂C₆H₃SCl to 2-(bicyclo[2.2.1]hept-5-en-2-ylidene)propanedinitrile ( 49 ) were not regioselective, showing that a dicyanomethylidene function is not like a carbonyl function when homoconjugated with a π system. The results are in agreement with predictions based on MO calculations suggesting that a carbonyl group homoconjugated with an electron-deficient centre can behave as an electron-donating, remote substituent because of favourable n(CO)?σC(1), C(2)?p(C(6) hyperconjugative interaction.     

(η3-allyl)palladium(II) catalysts for the addition polymerization of norbornene derivatives with functional groups

Cycloaliphatic polyolefins with functional groups were prepared by the Pd(II)-catalyzed addition polymerization of norbornene derivatives. Homo- and copolymers containing repeating units based on bicyclo[2.2.1] hept-5-en-2-ylmethyl decanoate (endo/exo-ratio = 80/20), bicyclo[2.2.1]hept-5-ene-2-carboxylic acid methyl ester (exo/endo = 80/20), bicyclo[2.2.1]hept-5-ene-2-methanol (endo/exo = 80/20), and bicyclo[2.2.1]hept-5-ene-2-carboxylic acid (100% endo) were prepared in 49–99% yields with {(η³-allyl)Pd(BF₄)} and {(η³-allyl)Pd(SbF₆)} as catalysts. The catalyst containing the hexafluoroantimonate ion was slightly more active than the tetrafluoroborate based Pd-complex.     

Synthesis and Characterization of New Thebaine Derivatives as Potential Opioid Agonists and Antagonists: 2‐[N‐(1H‐Tetrazol‐5‐yl)‐6,14‐endo‐etheno‐6,7,8,14‐tetrahydrothebaine‐7α‐yl]‐5‐phenyl‐1,3,4‐oxadiazoles

In this study, we report the synthesis a series of novel 2‐[N‐(1H‐tetrazol‐5‐yl)‐6,14‐endo‐etheno‐6,7,8,14‐tetrahydrothebaine‐7α‐yl]‐5‐phenyl‐1,3,4‐oxadiazole derivatives ( 7a – e ) which have potential opioid antagonist and agonist. The substitution reaction of 6,14‐endo‐ethenotetrahydrothebaine‐7α‐carbohydrazide with corresponding benzoyl chlorides gave diacylhydrazine compounds 4a – e in good yields. The treatment of compounds 4a – e with POCl₃ caused the conversion of side‐chain of compounds 5a – e into 1,3,4‐oxadiazole ring at C(7) position; thus, compounds 5a – e were obtained. Subsequently, cyanamides ( 6a – e ) were prepared from compounds 5a – e and then compounds 7a – e were synthesized by the azidation of 6a – e with NaN₃. The structures of the compounds were established on the basis of their IR, ¹H NMR, ¹³C APT, 2D‐NMR (COSY, NOESY, HMQC, HMBC) and high‐resolution mass spectral data.     

The π-Anisotropy of the Double Bond of a syn-11-Oxasesquinorbornene Derivative.. Stereoselectivity of the Diels–Alder additions of (2-norborneno)[c]furan. Crystal structure of 11-oxa-endo-tetracyclo[6.2.1.13,6.02,7]-dodec-2(7)-ene-9,10-exo-dicarboxylic anhydride

The reaction of (2-norborneno)[c]furan ( 4 ) with maleic anhydride gave 11-oxa-endo-tetracyclo[6.2.1.1^3,6.0^2,7]dodec-2(7)-ene-9,10-exo-dicarboxylic anhydride ( 5 ) and, with methyl acetylenedicarboxylate, methyl 11-oxa-endo-tetracyclo [6.2.1.1^3,6.0^2,7]dodeca-2(7),9-diene-9,10-dicarboxylate ( 7 ). The syn-11-oxa-sesquinorbornenes 5 and 7 could be equilibrated with their cycloaddents. They are at least 2 kcal/mol more stable than the corresponding anti-sesquinorbornenes 6 and 8 . The structure of 7 was deduced from its spectral data, by epoxidation with air or a peracid to give the exo-epoxide 13 and by catalytic hydrogenation to give 14 . The structure of 5 was established by single-crystal X-ray diffraction. A dihedral angle of 163° was measured between the C(1,2,7,8) and C(2,3,6,7) planes in 5 . This important deviation from planarity for the C(2,7) double bond is attributed to (π, ω)-repulsive interactions that make the π-electron density of 2-norbornene and 7-oxa-2-norbornene derivatives preferentially polarized toward the exo-face. This finding is discussed in relation with the relative stability of the syn- and anti- 11-oxasesquinorbornenes and with the endo-stereoselectivity of the cycloadditions of the norbornenofuran 4 .     

Reaction of Singlet Oxygen with 2-Methylnorborn-2-ene, 2-Methylidenenorbornane,and their 7,7-Dimethyl Derivatives. The transition state geometry for hydroperoxidation

The dye-sensitized photo-oxygenation of 2-methylnorbonr-2-ene ( 3 ), 2-methylidene-norbornane ( 4 ) and their 7,7-dimethyl derivatives ( 5 and 6 ) has been studied. In all cases allylically rearranged hydroperoxides were formed, except that 4 also gave a little norbornanone (presumably from the dioxetane) and 5 gave some endo-3,7,7-trimethylnorbornan-2-one as a secondary photo-product. It was found that the exo/endo attack ratios by singlet oxygen on 3 and 5 are 66 and 0.19. By exploiting the C (3) monodeuteriated derivatives, 4 and 6 showed ratios of 28 and 0.67. Rates of reactivity of the olefins 3 and 4 were compared to methylidenecyclopentane, 1-methylcyclopentene and 1-methylcyclohexene as monocyclic standards. Additionally, comparative rates between the 7,7-dimethyl olefins and their parents were measured. When further comparison was made of the rate ratios partitioned for exo and endo attack, it was seen that oxygen experienced a 500- to 1000-fold rate retardation on approach to the endo side of 3 compared to that for its monocyclic analogue. Exo rates between the parent norbornene 3 and its 7,7-dimethyl derivative 5 showed a 250-fold decrease. Although four times smaller than the difference reported for epoxidation, the evidence clearly pointed to a one-step cyclic process as the rate determining step for photo-oxygenation. The steric evidence, taken with the low values found for the intermolecular isotope effects of 1.14 ± 0.01 and 1.02 ± 0.01 observed for exo and endo-3-deuterio-2-methylidene-norbornanes, permits the deduction that the transition state is largely dipolar. In the early stages of the addition bonding between one end of the oxygen molecule and the terminal vinyl carbon is advanced. At the same time positive charge is dispersed by hyperconjugation between the central carbon atom and the allylic carbon-hydrogen bond. At a later stage the anionic oxygen atom abstracts the loosened allylic hydrogen atom to create the hydroperoxide. No evidence for the formation of a discrete perepoxide intermediate was obtained.     

A General Synthesis of Alkenyl‐Substituted Benzofurans,Indoles, and Isoquinolones by Cascade Palladium‐Catalyzed Heterocyclization/Oxidative Heck Coupling

Structurally diverse C3‐alkenylbenzofurans, C3‐alkenylindoles, and C4‐alkenylisoquinolones are efficiently prepared by using consecutive Sonogashira and cascade Pd‐catalyzed heterocyclization/oxidative Heck couplings from readily available ortho‐iodosubstituted phenol, aniline, and benzamide substrates, alkynes, and functionalized olefins. The cyclization of O‐ and N‐heteronucleophiles follows regioselective 5‐endo‐dig‐ or 6‐endo‐dig‐cyclization modes, whereas the subsequent Heck‐type coupling with both mono‐ and disubstituted olefins takes place stereoselectively with exclusive formation of the E isomers in most cases.     

Synthesis, Structure, and Derivatives of endo-4-Aminomethyltetracyclo[6.2.1.13,6.02,7]dodec-9-ene

Synthesis was performed and structure studied of endo-4-cyanotetracyclo[6.2.1.1^3,6.0^2,7]dodec-9-ene prepared by reaction of a stereochemically uniform endo-5-cyanobicyclo[2.2.1]hept-2-ene with cyclopentadiene. By analysis of potential energy surface (PES) for reactions of endo-5-cyanobicyclo[2.2.1]hept-2-ene and the respective exo-stereoisomer with cyclopentadiene (in B3LYP/6-31G(d) approximation) the endo,exo-junction and anti-orientation of the methylene bridges in the bicyclic fragments of the adducts were shown to be preferable. Reduction of the tetracyclic nitrile with lithium aluminum hydride yielded endo-4-aminomethyltetracyclo-[6.2.1.1^3,6.0^2,7]dodec-9-ene whose geometry and conformational characteristics were studied by means of molecular mechanics method. Products were obtained from reactions of the tetracyclic amine with p-toluene-, p-chloro-benzene-, p-nitrobenzenesulfonyl chlorides, p-nitrobenzoyl chloride, succinic anhydride, mesityl and p-toluene-sulfonyl isocyanates, phenyl, p-toluenesulfonyl, and benzoyl isothiocyanates, p-nitrophenyloxirane, and N-(2,3-epoxypropyl)carbazole. A series of the amine derivatives was epoxidized with perphtahlic acid. The structure of compounds synthesized was confirmed by analysis of their IR spectra, ¹H, ¹³C, and two-dimensional NMR spectra, and additionally by calculation of the chemical shifts in ¹H and ¹³C NMR spectra by procedures GIAO and CSGT in PBE1PBE/6-31G^## approximation.     

Die Hydrolyse von 6exo-substituierten 2exo- und 2endo-Norbornylestern der p-Toluolsulfonsäure. Norbornanreihe. 3. Mitteilung

The Hydrolysis of 6 exo -Substituted 2 exo - and 2 endo -Norbornyl p -Toluenesulfonates. Norbornane Series. Part 3 Hydrolysis of the 6exo-substituted 2exo- and 2endo-norbornyl p-toluenesulfonates 1b - 1 and 2b - 1 , respectively, in 70% dioxane led to different amounts of the following products: Unrearranged 2exo-norbornanols 3 and norbornenes 5 , accompanied in somes cases by small amounts of the rearranged Rendo-epimers 4 and 6 and by norticyclenes 7 . When the 6exo-substituent was a nucleophilic group as in 1e - 1 and 2e - 1 , various amounts of tricyclic products were also formed by endo-cyclization. These results show that the 2exo- and 2endo-esters 1 and 2 , respectively, react by way of different intermediates. In cases where the 6exo-substituent was an n-electron donor, as in 1m - r and 2m - r , quantitative fragmentation to (3-cyclopentenyl)acetaldehyde (13) occurred.     

Studies on metathetical and thermal polymerization of 5-norbornene 2,3-dicarboximide end-capped resins Pt-II

The article deals with synthesis, characterization, and polymerization of 5-norbornene-2,3-dicarboximide end-capped resins (bisnadimides) based on 4,4′-diaminodiphenylether, 1,4/1,3-bis(4′-aminophenoxy) benzene, 2,2′-bis[4-(4′-aminophenoxy)phenyl]propane, and bis[4-(4′-aminophenoxy)phenyl]sulphone. Both exo and endo bisnadimides were prepared by reacting the aromatic diamines with exo or endo nadic anhydride in glacial acetic acid at 120°C. The exo or endo bisnadimides could be distinguished on the basis of differences observed in IR or ¹H-NMR spectra. Both thermal (in solid state) and metathetical polymerization (using WCl₆/tetramethyltin catalyst and chlorobenzene solvent) of bisnadimides was carried out. Only exo bisnadimides could be polymerized using metathesis reaction whereas thermal polymerization of both endo and exo bisnadimide could be successfully carried out at 300°C in static air atmosphere. The polymers were highly crosslinked and insoluble in common organic solvents. The polymers obtained by metathesis polymerization were light brown in color whereas those obtained by thermal polymerization were dark brown in color. Thermal stability of the thermally polymerized exo or endo bisnadimides was comparable. These polymers were stable up to 400°C and decomposed in a single step above this temperature. The char yield at 800°C depended on the structure of the polymer and was in the 39–56% range. The polymers formed by metathesis polymerization showed a 1–3% weight loss in the temperature range 226–371°C and decomposed in a single step above 440°C. The char yields were higher in these polymers (53–71%) compared to those obtained by thermal polymerization. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2323–2331, 1997