Synthesis and gas separation properties of metathesis polynorbornenes with different positions of one or two SiMe3 groups in a monomer unit

The metathesis polymerization of 5,5-bis(trimethylsilyl)norbornene, 2,3-bis(trimethylsilyl)norbornadiene, and exo,endo-3,4-bis(trimethylsilyl)tricyclo[4.2.1.0^2,5]non-7-ene with the catalysts WCl₆/1,1,3,3-tetramethyl-1,3-disilacyclobutane, RuCl₃/EtOH, and the Grubbs Ru-carbene complex Cl₂(PCy₃)₂Ru=CHPh has been studied. New polymers with yields of up to 98% and M _w = (2?39) × 10⁵ are prepared. New metathesis copolymers of 5-trimethylsilylnorbonene with 5-(hydroxymethyl)norbornene and 5-(trimethylsiloxymethyl)norbornene are synthesized in the presence of the Cl₂(PCy₃)₂Ru=CHPh catalyst with yields of 78 and 98%. The gas-permeability study of the above series of the metathesis polymers containing one or two Me₃Si substituents in each monomer unit shows that the introduction of the second SiMe₃ group markedly improves their transport characteristics. A change in the character of the backbone (polynorbornadiene, polytricyclononene) has a small effect on the permeability of the polymers. The metathesis polynorbornene with two vicinal SiMe₃ groups exhibits higher gas-permeability coefficients than its isomer with germinal substituents. The homopolymer of 5-trimethylsilylnorbornene is characterized by better transport parameters than its copolymers with -OSiMe₃ and -OH substituents.     

Photochemische Umwandlungen. XV [1] Photochemische Isomerisierung des exo-Tricyclo[4.2.1.02′5]nona-3,7-dien-Systems. Vorläufige Mitteilung

The acetone sensitized isomerization of two exo-tricyclo[4.2.1.0^2,5]nonadiene derivatives, of the corresponding tricyclo[4.3.0.0^2,5]nonadienes, and the photoisomerization of two bicyclo[4.3.0]nonatrienes by direct excitation are described.     

Cooligomerization of allyl acetate with norbornadiene and its derivatives catalyzed by nickel complexes

Conclusions The cyclocooligomerization of allyl acetate with norbornadiene and its derivatives to compounds which are not readily accessible in the series tricyclo[4.2.1.0_2,5]nonane, tetracyclo[4.3.0.0_2,3.0^2,4]nonane and tetracyclo[4.4.1.0^2,5.0^7,10,]undecane has been achieved with yields of 60–95%, involving the participation of low-valency nickel complexes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 154–160, January, 1987.     

Ti-catalyzed reactions of 4,4′-bis(trimethylsilyl)bicyclohexyl-2,2′-diene with various electrophiles

Reductive disilylation (Li + Me₃SiCl − THF) of 1,3-cyclohexadiene led to 4,4′-bis(trimethylsilyl)bicyclohexyl-2,2′-diene (1). In the presence of TiCl₄ in dichloromethane, 1 reacted with some acyl chlorides, anhydrides, and aldehydes to give tricyclo[7.4.0.0^3,8]trideca-4,12-diene-2-yl derivatives.     

Hinged bis-porphyrin scaffolds I. The synthesis of a new porphyrin diene and its role in constructing hinged porphyrin dyads and cavity systems

Norbornene building BLOCKs formed by the reaction of porphyrin 1,3-dienes with norbornadiene or dimethyl tricyclo[4.2.1.0^2,5]nona-2,7-diene-3,4-dicarboxylate were coupled with an ester-activated cyclobutene epoxide BLOCK to afford the first examples of hinged porphyrin-spacer-acceptor dyads. Similar dual coupling with a bis-(cyclobutene epoxide) formed doubly hinged POR-spacer-POR scaffolds separated by up to 16σ-bonds. The ability of the doubly hinged ZnPOR-16σ-ZnPOR scaffold to adopt cavity-shaped conformations was indicated by semiempirical AM1 calculations of these conformationally flexible bis-porphyrin scaffolds.     

Rearrangement of substituted tricyclo[2.1.0.02,5]pentan-3-ones

Treatment of 1,5-bis(hydroxymethyl)tricyclo[2.1.0.0^2,5]-pentan-3-one (III) with triphenyl phosphine and carbon tetrachloride results in deep-seated rearrangement to the keto furan, 3-oxybicyclo-[3.3.0]octa-1,4-dien-7-one, VI; the analogous reaction with carbon tetrabromide is normal and yields, the anticipated dibromide IV. Cyclopentadienone intermediates account for the latter reaction and for a dimer formed from 1,5-dimethyltricyclo[2.1.0.0^2,5] pentanone (Ia) upon treatment with iodine.     

Trifluoromethyl substituted ring systems: synthesis,and reactivity towards metal carbonyls

Hexafluoro-but-2-yne and actafluoro-but-2-ene both readily add to cyclopentadiene. Similar Diels-Alder reactions occur between hexafluoro-but-2-yne and cycloheptatriene and cyclooctatetraene. 2,3-Bis(trifluoromethyl)bicyclo[2.2.1]hepta-2,5-diene reacts with chromium and molybdenum hexacarbonyls, and with enneacarbonyl di-iron to give metal complexes [M(diene)(CO)₄] (M = Cr, Mo) and [Fe(diene)(CO)₃], respectively. 6,7-Bis-(trifluoromethyl)tricyclo[3.2.2.0^2,4]nona-6,8-diene obtained from hexafluoro-but-2-yne and cycloheptatriene and 7,8-bis(trifluoromethyl)tricyclo[4.2.2.0^2,5]deca-3,7,9-triene formed from hexafluoro-but-2-yne and cyclooctatetraene also react with molybdenum hexacarbonyl to form complexes of molybdenum di- and tetracarbonyl groups, respectively. ¹H, ¹⁹F and ¹³C n.m.r. spectra of the compounds are described.     

Asymmetric ruthenium‐catalysed [2+2] cycloadditions between bicyclic alkenes and chiral aryl‐substituted acetylenic acyl camphorsultam alkynes

The regio‐ and absolute stereochemistry of (7S)‐N‐[4‐(3‐thienyl)tricyclo[4.2.1.0^2,5]non‐3‐en‐3‐ylcarbonyl]‐2,10‐camphorsultam tetrahydrofuran hemisolvate, C₂₄H₂₉NO₃S₂·0.5C₄H₈O, and (7S)‐N‐[4‐(4‐tolyl)tricyclo[4.2.1.0^2,5]non‐3‐en‐3‐ylcarbonyl]‐2,10‐camphorsultam, C₂₇H₃₃NO₃S, have been established. One contains a half‐occupancy tetrahydrofuran solvent molecule located on a twofold axis and the other contains two crystallographically unique molecules which are nearly identical. The extended structures of both complexes can be explained via weak C—H...O interactions, which link the molecules together into two‐dimensional sheets in the ab plane for the thienyl complex and ultimately into a three‐dimensional structure for the tolyl derivative. The stereochemistry of both structures confirms that [2+2] cycloadditions of bicyclic alkenes and alkynes catalysed by ruthenium are exclusively exo.     

Defined synthesis of copolymers using metallocene catalysis

The copolymerization of propene with small amounts of ethene, catalyzed by tetrahydroindenyl zirconocenes such as [En(H₄Ind)₂]ZrCl₂ or [Me₂Si(H₄Ind)₂]ZrCl₂ and MAO in liquid propene produces polymers with much higher activities and molecular weights than the homopolymerization of propene. The normal bisindenyl complexes doesn't present such differences. The investigation of the microstructure shows for the tetrahydroindenyl catalyst that after a 2,1-insertion of a propene unit the system is in a sleeping state and can be activated when an ethene unit is inserted. In this case these catalysts become faster than the ansa bis-indenyl catalysts. An active catalyst for the copolymerization of ethene and norbornene is the more temperature stable [Me₃PhPen(Flu)]ZrCl₂. This catalyst produces atactic copolymers with high molecular weights of over 900 000 g/mol at 30°C and 38 mol% of norbornene content.     

Synthesis of Substituted Pyrrolo[3,4‐a]carbazoles

The cycloaddition between N‐protected 3‐{1‐[(trimethylsilyl)oxy]ethenyl}‐1H‐indoles and substituted maleimides (= 1H‐pyrrole‐2,5‐diones) yielded substituted pyrrolo[3,4‐a]carbazole derivatives bearing an additional succinimide (= pyrrolidine‐2,5‐dione) moiety either at C(5a) or C(10b) depending on the type of the protection group at the indole N‐atom. Derivatives substituted at C(10b) were isolated when the protection group, Me₃Si or Boc (^tBuOCO), was eliminated during the reaction (Schemes 2 and 3), whereas a substitution at C(5a) was observed when an electron‐withdrawing group, Tos (4‐MeC₆H₄SO₂) or pivaloyl (Me₃CCO), was not eliminated (Scheme 1). Complex results were found in reactions between 1‐(trimethylsilyl)‐3‐{1‐[(trimethylsilyl)oxy]ethenyl}‐1H‐indole, in contrast to formerly reported results (Scheme 3). Some derivatives of 1H,5H‐[1,2,4]triazolo[1′,2 : 1,2]pyridazino[3,4‐b]indole‐1,3(2H)‐dione were obtained from reactions with 4‐phenyl‐3H‐1,2,4‐triazole‐3,5(4H)‐dione (Scheme 2). All structures were established by spectroscopic data, by calculations, and one representative structure was confirmed by an X‐ray crystallographic analysis (Fig.). Finally, the formation of the different structure types was discussed, and compared with similar reactions reported in the literature.     

Regiospecific Displacement of the C-B Bond of Tris[4-(substituted)furan-3-yl]boroxines with C-Sn Bond and C-O Bond: Syntheses of 3,4-Disubstituted Furans and 4-Substituted-3(2H)-furanones,

Tris[4-(substituted)furan-3-yl]boroxines 2 , prepared from the corresponding 4-(substituted)-3-(trimethylsilyl) furan 1, were converted successfully to 4-(substituted)-3-(tributylstannyl)furans 3 through palladium-catalyzed cross-coupling reactions with tributylstannyl chloride. Palladium-catalyzed cross-coupling reactions of 3 with organohalides afforded 3,4-disubstituted furans 4 . Regiospecific iodination of 4-(trimethylsilyl)-3-((tributylstannyl) furan ( 3a ) gave 4-iodo-3-(trimethylsilyl)furan ( 5 ), which reacted with excess ethyl acrylate under a common Heck-condition to produce 2,3-bis(trans-ethoxycarbonylvinyl)-4-(trimethylsilyl)furan ( 6 ). A thermal 6-electrocyclic reaction followed by dehydration converted 6 into benzo[2,3-6]furan 8 . Oxidation of 2 generated the corresponding 4-substituted-3(2H)-furanones 9 .     

Reactions of quadricyclane with fluorinated nitrogen-containing compounds. Synthesis of 3-aza-4-perfluoroalkyl-tricyclo[4.2.1.0]non-3,7-dienes

The cycloaddition reactions of quadricyclane (1) and polyfluorinated imines and nitriles were studied. Both (CF₃)₂CNH and (CF₃)₂CN(2-FC₆H₄) were found to have low reactivity towards 1, giving the corresponding [2 + 2 + 2] cycloadducts in a low yield. C₂F₅NCFCF₃ however, reacts with 1 rapidly, giving a mixture of two isomeric cycloadducts in a high yield. Perfluoroalkyl nitriles R_fCN (R_f = CF₃, C₂F₅, n-C₃F₇) were found to have surprisingly high reactivity to 1 producing exo-3-aza-4-(fluoroalkyl)-tricyclo[4.2.1.0^2,5]non-3,7-dienes in 56-81% yields at elevated temperature. Exo-3-aza-4-(perfluoroalkyl)-tricyclo[4.2.1.0^2,5]non-3,7-dienes rapidly react with CF₃Si(CH₃)₃ in the presence of CsF catalyst. The reaction results in addition of CF₃Si(CH₃)₃ across the CN bond of the azadienes with selective formation of only one stereoisomer of exo-3-aza-3-(trimethylsilyl)-4,4-bis(perfluoroalkyl)-tricyclo[4.2.1.0^2,5]non-7-enes. Silyl group in this compounds can be removed either by the action of tetrabutylammonium fluoride hydrate, leading to the formation of the corresponding amine after hydrolysis, or by reaction with HCl resulting in the formation of the corresponding amine hydrochloride.     

On the syntheses and some reactions of bis- and tris(methylthio)thiophenes

Reaction between various thienyllithium derivatives and dimethyl disulfide has been used for the preparation of 2,5-, 2,3-, and 3,4-bis(methylthio)thiophenes, as well as 2,3,4- and 2,3,5-tris(methylthio)thiophenes. Bromination of (methylthio)thiophenes with N-bromosuccinimide was found to be most convenient for the preparation of brominated (methylthio)thiophenes such as 3-bromo-2,5-bis(methylthio)- and 5-bromo-2,3-bis(methylthio)thiophene, 3,4-dibromo-2,5-bis(methylthio)-, 2,5-dibromo-3,4-bis(methylthio)- and 2,3-dibromo-4,5-bis(methylthio)thiophene as well as 3-bromo-2,4,5-tris(methylthio)thiophene. The reaction of methylthio substituted thienyllithium derivatives with methyl chloroformate was used for the syntheses of methyl methylthio substituted thiophenecarboxylates and using 1/3 of an equivalent for the direct preparation of methylthio substituted 3-thienylcarbinols as tris[2,4,5-tris(methylthio)-3-thienyl]carbinol.     

The Photolysis of Tricyclo[4.2.1.02,5]nonadiene: Support of a Doughert ‘type N’ mechanism from photoelectron spectroscopical studies

In earlier work on the photolysis of derivatives of tricyclo[4.2.1.0^2,5]nonadiene (I), the intermediacy of a biallyl-like structure has been postulated which is formed by C₁-C₂ bond cleavage of I in its first excited state. This mechanism is now supported by the results of photoelectron spectroscopical studies on I and its two dihydroderivatives. Further support is gained from the theoretically calculated Ehrenson C₁-C₂-bond indices for the ground and the first excited state of these molecules. While the results for I in principle can be rationalized on the (one-electron) basis of ‘through bond’ interaction between the two π-bonds, the absence of C₁-C₂ photocleavage for a substituted tricyclo[4.2.2.0^2,5]decadiene also requires consideration of an (all-electron) thermochemical driving force.     

Preparation of 1,1-disubstituted silacyclopentadienes

Several new 1,1-disubstituted siloles containing substituents on the ring carbon atoms have been synthesized. The new siloles: 1,1-dihydrido-2,5-bis(trimethylsilyl)-3,4-diphenylsilole (5), 1,1-dihydrido-2,5-dimethyl-3,4-diphenylsilole (6), 1,1-dimethoxy-2,5-bis(trimethylsilyl)-3,4-diphenylsilole (7), 1,1-bis(4-methoxyphenyl)-2,5-bis(trimethylsilyl)-3,4-diphenylsilole (8), 1,1-dipropoxy-2,5-bis(trimethylsilyl)-3,4-diphenylsilole (9), and 1,1-dibromo-2,5-bis(trimethylsilyl)-3,4-diphenylsilole (13) were prepared from reactions originating from the previously reported, 1,1-bis(diethylamino)-2,5-bis(trimethylsilyl)-3,4-diphenylsilole (1) or 1,1-bis(diethylamino)-2,5-dimethyl-3,4-diphenylsilole (2). In addition, three other new organosilane byproducts were observed and isolated during the current study, bis(4-methoxyphenyl)bis(phenylethynyl)silane (11), bis(4-methoxyphenyl)di(propoxy)silane (12) and 1-bromo-4-bromodi(methoxy)silyl-1,4-bis(trimethylsilyl)-3,4-diphenyl-1,3-butadiene (14). Compounds 13 and 14 were characterized by X-ray crystallography and 14 is the first 1,1-dibromosilole whose solid state structure has been determined.     

Straightforward synthesis of phosphametallocenium cations of Rh and Ir

Reaction of 3,4-dimethylphospholylthallium (Tl-1) with [Cp^∗MCl₂]₂ (M = Rh, Ir) leads to the formation of the dimeric species [(Cp^∗M)₂(Me₂C₄H₂P)₃]⁺2 and 3 with bridging μ-η¹:η¹-phospholyl ligands. The phosphametallocenium sandwich complexes [Cp^∗M(Me₂C₄(SiMe₃)₂P)]⁺7 (M = Rh) and 8 (M = Ir) could be obtained from the reaction of [Cp^∗MCl₂]₂ and the 2,5-bis(trimethylsilyl)-1-trimethylstannylphosphole 6, with the bulky trimethylsilyl groups preventing the phosphole from η¹- and enforcing a η⁵-coordination. The structures of phospharhodocenium cation 7 and a byproduct 9 containing a phosphairidocenium moiety could be determined by X-ray diffraction.     

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).     

Synthesis of new imines and amines containing organosilicon groups

The Peterson olefination reaction of terephthalaldehyde with tris(trimethylsilyl)methyl lithium, (Me₃Si)₃CLi, in THF at 0 °C gives 4-[2,2-bis(trimethylsilyl)ethenyl]benzaldehyde (1) and 4,4-bis[2,2-bis(trimethylsilyl)ethenyl]benzene (2). The new aldehyde (1) reacts with variety of amines in ethanol to afford the corresponding imines (3) containing vinylbis(trimethylsilyl) group. The newly synthesized imines (3) can be completely converted into amines containing vinylbis(trimethylsilyl) group with an excess amount of NaBH₄. In the case of N-[4-(2,2-bis(trimethylsilyl)ethenyl)benzyl]-2,6-dimethylaniline LiAlH₄ was used as a reducing agent in THF.     

Ring‐opening metathesis polymerization of amino acid‐functionalized norbornene derivatives

Amino acid‐derived novel norbornene derivatives, N,N′‐(endo‐bicyclo[2.2.1] hept‐5‐en‐2,3‐diyldicarbonyl) bis‐L ‐alanine methyl ester (NBA), N,N′‐(endo‐bicyclo[2.2.1]hept‐5‐en‐2,3‐diyldicarbonyl) bis‐L ‐leucine methyl ester (NBL), N,N′‐(endo‐bicyclo[2.2.1]hept‐5‐en‐2,3‐diyldicarbonyl) bis‐L ‐phenylalanine methyl ester (NBF) were synthesized and polymerized using the Grubbs 2nd generation ruthenium (Ru) catalyst. Although NBA, NBL, and NBF did not undergo homopolymerization, they underwent copolymerization with norbornene (NB) to give the copolymers with M_n ranging from 5200 to 38,100. The maximum incorporation ratio of the amino acid‐based unit was 9%, and the cis contents of the main chain were 54–66%. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5337–5343, 2006     

Isoquinolinium N-arylimides and strained cycloalkenes

In contrast to common alkenes and enol ethers, the angle-strained double bonds of norbornene, dimethyl norbornadiene-2,3-dicarboxylate, and acenaphthylene undergo [3+2] cycloadditions with isoquinolinium N-arylimides. The structures of the crystalline adducts have been elucidated from their ¹H nmr spectra.