The synthesis and characterisation of poly( 14-cyclopentenylene-5,6-ethylidene-2,3-disodium dicarboxy1ate)s and Pendant functional group isomerisation

Summary Poly(l,4-cyclopentenylene-5,6-ethylidene-2,3-disodium dicarboxy1ate)s have been synthesised from the exo,exo-, endo,endo- and exo, endo- isomers of dimethyl bicyclo[2.2.l]hept-5-ene-2,3-dicarboxylates in a three step process involving ring opening metathesis polymerisation, hydrogenation and hydrolysis. Exo,exo- and endo,exo- pendant functional group stereochemistries were unchanged throughout these processes, whereas, the Polymers derived from the endo,endo-monomer underwent fragmentation during hydrogenation and isomerisation during hydrolysi s to give to the more stable endo,exo- form of the polymer. Received: 25 July 2002/ Accepted: 7 October 2002 Correspondence to W. J. Feast     

Field bioassay ofexo- andendo-brevicomin withDendroctonus ponderosae in lodgepole pine

Bothexo- andendo-brevicomin reduced the response of flyingDendroctonus ponderosae (Coleoptera: Scolytidae) to an attractant composed oftrans-verbenol and terpenes or oftrans- andcis-verbenol and terpenes in a stand ofPinus contorta var.murrayana. These data suggest that racemicexo- andendo-brevicomin may interrupt aggregation in populations of mountain pine beetle colonizing lodgepole pine; functions of the natural chiral compounds are unknown.Research supported by NSF grants DEB 77-11367 and PCN 79-21708 and the O.S.U. School of Forestry. O.S.U. Agric. Exp. Sta. Tech. Paper No. 5713.     

Isomerization of tetrahydrodicyclopentadiene using ionic liquid: Green alternative for Jet Propellant-10 and adamantane

The isomerization of endo-tetrahydrodicyclopentadiene (endo-THDCPD) to exo-THDCPD (Jet Propellant-10) and adamantane was investigated using ionic liquid (IL) as acid catalyst to explore an alternative greener than widely applied AlCl₃-based operation. ILs composed of various 1-alkyl-3-methylimidazolium chlorides ([RMIM]Cl) and metal chlorides were checked, and [BMIM]Cl/AlCl₃ was the best. The effects of acidity and dosage of IL, reaction temperature and time were studied for endo- to exo-isomerization of THDCPD. The reaction occurs quickly under mild conditions with both conversion and selectivity beyond 98%. Purifying the reactant can suppress deactivation of IL; and the used IL can be recycled four times by heating under vacuum after each run. By adjusting the reaction to severe conditions, i.e. higher IL dosage, higher temperature and longer time, exo-THDCPD is further isomerized to adamantane. But both the conversion and selectivity are much lower than those of endo- to exo- isomerization. The highest yield of adamantane is 50.9%, which can be further improved by some additives like 1-bromoadamantane. Compared with other methods, IL catalysis has many advantages from energy and environmental perspectives.     

Field responses of the western pine beetle1 and one of its predators to host- and beetle-produced compounds

The responses of the western pine beetle (Dendroctonus brev-icomis LeConte) andTemnochila chlorodia (Mannerheim) to candidate attractants—exo- andendo-brevicomm, frontalin,trans-verbenol, ver-benone, and ponderosa pine turpentine and its major monoterpene components—were quantified by counts of beetles on traps baited with the various attractants, singly and in combinations released simultaneously. Combinations ofexo-brevicomin and frontalin plus a monoterpene or turpentine were the most attractive toD. brevicomis. The responses to these attractant combinations were reduced when verbenone plustrans-verbenol were present. All single compounds and binary mixtures, exceptexo-brevicomin plus frontalin, were much less attractive.exo-Brevicomin was most attractive toT. chlorodia, and this response appeared to decrease when verbenone plustrans-verbenol were present.Coleoptera: Scolytidae.Coleoptera: Trogositidae.This research was supported in part by the Forest Service, U.S. Department of Agriculture, and in part by grants from the Rockefeller Foundation to the University of California. Commercial enterprises and products are mentioned solely for information, and do not imply endorsement by the sponsoring agencies and organizations.     

Synthesis of novel polymeric HALS stabilizers and chain transfer effect of hindered amine norbornene derivatives on ring-opening metathesis polymerization

Cyclooctadiene (COD) was polymerized via ring-opening metathesis polymerization (ROMP) in the presence of 5-norbornene-exo, endo-2-carboxylic acid 2,2,6,6-tetramethyl-4-piperidinyl ester (PN) or 5-norbornene-2-exo-3-endo-dicarboxylic acid bis(2,2,6,6-tetramethyl-4-piperidinyl) ester (2,3-PN) to prepare a new kind of polymeric hindered amine (HALS) stabilizers. Unexpectedly, hindered amine norbornene derivatives PN and 2,3-PN did not act as comonomer but acted as chain transfer agent (CTA). The resulting polymers were characterized by gel permeation chromatography (GPC) and ¹H-NMR. Investigation of polymerization behavior showed that hindered amine groups were introduced into polymer chain by virtue of chain degradation resulted from chain transfer. The molecular weight (M _n) and HALS content of the resulting polymeric HALS stabilizer could be regulated by varying molar ratio of initial monomer to catalyst.     

Ring-opening metathesis polymerization of amino acid-functionalized norbornene diester monomers

Amino acid-derived novel norbornene diester derivatives, 5-norbornene-endo,endo-2,3-dicarboxylic acid bis((S)-2-N-(tert-butoxycarbonyl)aminopropyl) ester (1a), 5-norbornene-exo,exo-2,3-dicarboxylic acid bis((S)-2-N-(tert-butoxycarbonyl)aminopropyl) ester (1b), bis(N-α-(tert-butoxycarbonyl)-l-alanine) 5-norbornene-2,3-endo,endo-dimethyl ester (2a), bis(N-α-(tert-butoxycarbonyl)-l-alanine) 5-norbornene-2,3-exo,exo-dimethyl ester (2b) were synthesized and polymerized by the Grubbs catalyst, 2nd generation. Ring-opening metathesis polymerization of the monomers satisfactorily proceeded to give the polymers with fairly high molecular weights in good yields. The polymerization rate was not affected by the stereostructure of the monomers, endo,endo- and exo,exo-, while largely affected by solvents. The order of polymerization rate was as follows: acetone-d₆ > benzene-d₆ > DMF-d₇ ≈ CD₂Cl₂ > CDCl₃.     

Regioselective Synthesis of Naphtho‐fused Heterocycles via Palladium(0)‐Catalyzed Tandem Reaction of N‐Tosylhydrazones

We have developed a palladium(0)‐catalyzed tandem process which involves the cross‐coupling reaction of N‐tosylhydrazones with dibromide compounds followed by a sequence of intramolecular 5‐exo‐trig, 3‐exo‐trig cyclization, ring opening, and β‐hydride elimination to produce 6‐endo‐trig cyclized products. The strategy was successfully applied for the regioselective synthesis of substituted benzo[b]naphtho[2,1‐d]thiophenes, naphtho[1,2‐b]benzofurans, and benzo[a]carbazoles in moderate to excellent yields.

     

Organocatalytic and Stereoselective [3 + 2] Cycloadditions of Azomethine Imines with α,β‐Unsaturated Aldehydes

Bipyrazolidin‐3‐one derivatives are biologically significant compounds and their importance has increased in the past decades. In this paper, the first stereoselective [3 + 2] dipolar cycloadditions of azomethine imines with α,β‐unsaturated aldehydes catalyzed by readily available α,α‐diarylprolinol salts are reported, providing a facile route to the synthesis of various chiral bipyrazolidin‐3‐one derivatives under mild conditions. The organocatalyst 1 g with strongly electron‐withdrawing groups exhibited the best stereoselectivity (exo:endo up to 98:2, for exo product up to 97 % ee), in the combination with trifluoroacetic acid.     

An unusual epimerization of a thioether

Reaction of 6-exo-methylthio-2-exo-phenylbicyclo[2.2.1]heptan-2-endo-ol with sodium azide and acid afforded the corresponding 2-exo-azide. This azide was reduced and acetylated to give a crystalline derivative whose structure was unequivocally established by X-ray crystallographic analysis. Surprisingly, the isomeric 6-endo-methylthio-2-exo-phenylbicyclo[2.2.1]heptan-2-endo-ol on reaction with sodium azide and acid yielded the same azide as the 6-exo-methylthio analogue. Evidence for the mechanism of thioisomerization is presented.     

Synthesis and characterization of hydrogenated poly(norbornene endo-dicarboximide)s prepared by ring opening metathesis polymerization

Poly(norbornene imide)s prepared by ring opening metathesis polymerization (ROMP) have been generally synthesized from 5-norbornene-exo,exo-2,3-dicarboximides (exo-NDIs), since 5-norbornene-endo,endo-2,3-dicarboximides (endo-NDIs) exhibit considerably lower reactivity toward conventional ROMP catalysts as compared with exo-NDIs. Therefore, there has been limited information on poly(endo-NDI)s, although the endo-stereoisomer monomers are the principal products in Diels–Alder reaction between cyclopentadiene and maleimides. Here we synthesized various poly(endo-NDI)s using available Grubbs catalysts, and subsequently hydrogenated their backbone double bonds to obtain high molecular weight samples with M_n > 150,000. The thermal, thermo-mechanical, mechanical, and optical properties of poly(endo-NDI)s before and after hydrogenation were then investigated, together with the structural properties by wide-angle X-ray scattering and refractive index, in comparison with those of the corresponding poly(exo-NDI)s. Surprisingly, poly(endo-NDI)s exhibit significantly higher glass transition temperatures (by ca. 34 °C) and refractive index values than the exo-counterparts, probably due to increased intermolecular packing. Other properties such as thermal stability, tensile modulus, coefficient of thermal expansion, optical transparency, water absorption, and water transmission rate are quite comparable. Overall, convenient monomer preparation coupled with attractive physical properties makes poly(endo-NDI)s very interesting for practical applications such as optical films and flexible substrates for optoelectronics.     

Unusual CC Bond Isomerization of an α,β‐Unsaturated γ‐Butyrolactone Catalysed by Flavoproteins from the Old Yellow Enzyme Family

An unexpected, redox‐neutral C?C bond isomerization of a γ‐butyrolactone bearing an exo‐methylene unit to the thermodynamically more favoured endo isomer (k_cat=0.076 s^?1) catalysed by flavoproteins from the Old Yellow Enzyme family was discovered. Theoretical calculations and kinetic data support a mechanism through which the isomerization proceeds through FMN‐mediated hydride addition onto exo‐Cβ, followed by hydride abstraction from endo‐Cβ′, which is in line with the well‐established C?C bond bioreduction of OYEs. This new isomerase activity enriches the catalytic versatility of ene‐reductases.     

Synthesis of new fluorine containing ring-opened polynorbornene dicarboximides using ruthenium alkylidene catalysts

Summary  The synthesis of new N-4-trifluoromethylphenyl-exo-endo-norbornene-5,6-dicarboximide (TFmNDI, 2a) and N-3,5-difluorophenyl-exo-endo-norbornene-5,6-dicarboximide (DFNDI, 2b) was carried out. Polynorbornene dicarboximides, 3a and 3b, were obtained via ring opening metathesis polymerization (ROMP) using bis(tricyclohexylphosphine) benzylidene ruthenium(IV) dichloride (I) and tricyclohexylphosphine [1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene][benzylidene] ruthenium dichloride (II), respectively. T_g’s for polymers 3a and 3b were observed at 155 C and 142 C, respectively. Compared to polymer 3b, polymer 3a with the bulky trifluoromethyl group showed the highest glass transition temperature and improved mechanical properties.     

Artificial Metalloenzymes with the Neocarzinostatin Scaffold: Toward a Biocatalyst for the Diels–Alder Reaction

A copper(II) cofactor coupled to a testosterone anchor, copper(II)‐(5‐(Piperazin‐1‐yl)‐1,10‐phenanthroline)testosterone‐17‐hemisuccinamide ( 10 ) was synthesized and associated with a neocarzinostatin variant, NCS‐3.24 (K_D=3 μm ), thus generating a new artificial metalloenzyme by following a “Trojan horse” strategy. Interestingly, the artificial enzyme was able to efficiently catalyze the Diels–Alder cyclization reaction of cyclopentadiene ( 1 ) with 2‐azachalcone ( 2 ). In comparison with what was observed with cofactor 10 alone, the artificial enzymes favored formation of the exo products (endo/exo ratios of 84:16 and 62:38, respectively, after 12 h). Molecular modeling studies assigned the synergy between the copper complex and the testosterone (K_D=13 μm ) moieties in the binding of 10 to good van der Waals complementarity. Moreover, by pushing the modeling exercise to its limits, we hypothesize on the molecular grounds that are responsible for the observed selectivity.     

Regio- and stereoselective synthesis of pyrrolo or azepine-fused cyclopenta[d]isoxazolines from 2-p-tolylsulfinylcyclopent-2-en-1-one

Reactions of enantiopure 2-p-tolylsulfinylcyclopent-2-en-1-one with cyclic nitrones afforded pyrrolo or azepine-fused cyclopenta[d]isoxazolidines in high yields under mild conditions. Comparison of these results with those obtained with cyclopent-2-en-1-one as the dipolarophile shows that the sulfinyl group increases the reactivity of the enonic system and efficiently controls the π-facial and endo/exo selectivities of the cycloadditions, which are also dependent on the easy cycloreversion of the resulting compounds. Results obtained in reactions with other dipoles (benzonitrile oxides and those resulting from allenoate and PPh₃) are also reported.     

Improved conversion of 6‐endo‐tosyloxybicyclo[2.2.2]octan‐2‐ones into 6‐exo‐acetoxy and 6‐exo‐benzoyloxybicyclo[2.2.2]octan‐2‐ones

The reaction conditions for the conversion of 6‐endo‐tosyloxybicyclo[2.2.2]octan‐2‐one ( 7b ) into 6‐exo‐acetoxy ( 8b ) and 6‐exo‐benzoyloxybicyclo[2.2.2]octan‐2‐one ( 8a ), respectively, were improved. Thus known 6‐endo‐tosyloxy‐bicyclo[2.2.2]octan‐2‐ones (+)‐(1RS,6SR,8SR,11RS)‐11‐[(4‐toluenesulfonyl)oxy]tricyclo[6.2.2.0^1,6]dodecan‐9‐one ( 1a ), 13‐methyl‐15‐oxo‐9β,13b‐ethano‐9β‐podocarpan‐12β‐yl‐4‐toluenesulfonate ( 3a ), and methyl (13R)‐16‐oxo‐13‐[(4‐tolylsulfonyl)oxy]‐17‐noratisan‐18‐oate ( 5 ), were converted,in comparable yields, as previously recorded, but much shorter times, into (+)‐(1RS,6SR,8SR,11SR)‐11‐(benzoyloxy) tricyclo[6.2.2.0^1,6]dodecan‐9‐one ( 2 ), 13‐methyl‐15‐oxo‐9β,13β‐ethano‐9β‐podocarpan‐12α‐yl benzoate ( 4 ), and methyl (13S)‐13‐(benzoyloxy)‐16‐oxo‐17‐noratisan‐18‐oate ( 6 ), respectively.     

Benzyl Cation Initiated Intramolecular Cyclizations. Synthesis of 1-azabicyclo[3.2.1]octene derivatives

Benzyl cation inititiated intramolecular cyclization reactions with conjugated C C double bonds were performed providing rac. endo-exo isomers of 1-azabicyclo[3.2.1]octenes ( 2 and 3 ). Formation of the endo isomer 2 is favoured. Compounds 2 possess dopamine uptake inhibitory effect with an additional selective MAO-B enzyme inhibitory potential. The remarkable in vitro effects do not correspond to in vivo antidepressant activity.     

Preparation of high energy fuel JP-10 by acidity-adjustable chloroaluminate ionic liquid catalyst

The isomerization of endo-tetrahydrodicyclopentadiene (endo-THDCPD) to its exo-isomer (JP-10) has been investigated by using chloroaluminate ionic liquids (ILs) as catalysts. The catalyst activity and selectivity could be optimized by varying the mole fraction of AlCl₃ in the IL. Undesirable by-products derived from side-reactions such as skeletal rearrangement, alkylation, cracking, and dimerization could be minimized by appropriate catalyst design and adjustment of the reaction conditions. The catalyst system was further optimized by selecting 1-butyl-3-methylimidazolium chloride as the basic IL and adding 0.60-0.65 mole fraction of AlCl₃ as the promoter. Using the optimized catalyst system, the isomerization of endo-THDCPD to exo-THDCPD proceeded at a fast rate at 50 °C with 98.9% conversion and 100% selectivity. The catalyst longevity has been demonstrated by recycling the IL several times without a noticeable reduction in catalytic activity.     

MgCl2‐supported TiCl4 catalysts containing diethyl norbornene‐2,3‐dicarboxylate internal electron donor for 1‐butene polymerization: Effects of internal electron donor configuration

Three isomeric 5‐norbornene‐2,3‐dicarboxylic acid diethyl ester (NDDE) with endo‐, exo‐, and trans‐configuration have been synthesized and employed as internal electron donors (IED) in 1‐butene polymerization over magnesium chloride supported Ziegler–Natta catalysts. It was found that the configuration of NDDE plays a key role in tuning the catalyst activity, stereospecificity, molecular weight (MW), and polydispersity index (PDI) of resulting poly(1‐butene). The type of catalyst with cis‐5‐norbornene‐endo‐2,3‐dicarboxylic acid diethyl ester as IED shows the highest catalyst activity, while catalyst with trans‐NDDE as IED yields the poly(1‐butene) with the highest MW and the most broad PDI. IR results showed that the NDDE with endo‐, exo‐, and trans‐configuration have different coordination way to MgCl₂, subsequently affecting the catalysts performance. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40758.     

Phosphaannulation of Aryl‐ and Benzylphosphonic Acids with Unactivated Alkenes via Palladium‐Catalyzed C?H Activation/Oxidative Cyclization Reaction

An efficient phosphaannulation via palladium(II)‐catalyzed C H activation/oxidative cyclization by the 6‐endo mode is reported for the synthesis of 3‐substituted phosphaisocoumarins from the reaction of arylphosphonic acids with unactivated alkenes under aerobic conditions. Also, α,α‐disubstituted benzylphosphonic acids were phosphaannulated with unactivated alkenes, producing phosphaisochromanones having (Z)‐alkylidenyl groups via anti‐phosphoryloxypalladation by the 6‐exo mode.

     

Frontalin in the male mountain pine beetle

Frontalin andexo-brevicomin were identified by GC-MS in air drawn over maleDendroclonus ponderosae Hopk. (MPB) from Oregon that had joined females for 1–2 days in the bark of lodgepole and ponderosa pine logs. Unfed males releasedexo- andendo-brevicomin but not frontalin. These three compounds were not detected in either unfed or fed females. Arrestment of males bytrans-verbenol and terpenes in an olfactory walkway was reduced by the addition of racemic frontalin; production of attractant chirps also diminished. Racemic frontalin also strongly reduced the aggregation of MPB in lodgepole and ponderosa pine stands to sticky traps baited with the aggregation pheromonetrans-verbenol and host terpenes; however, the function of the natural enantiomer of frontalin in MPB is unknown.Research supported by NSF Grant PCN 79-21708. O.S.U. Agricultural Experiment Station Technical Paper No. 6219.