E. Sh. Finkel'shtein

Synthesis and gas permeation properties of new ROMP polymers from silyl substituted norbornadienes and norbornenes

Abstract Using ring opening metathesis polymerization (ROMP) the novel linear polynorbornadiene and polynorbornene (PNB) derivatives bearing silicon-containing moieties were prepared in the presence of RuCl 3 ·3H 2 O, RuCl 2 (PPh 3 ) 3 , and WCl 6 /tetramethyldisilacyclobutane catalysts with the yields up to 98%. Gas permeation properties (permeability and diffusion coefficients) of the polymers obtained were measured. It was shown that polynorbornadiene containing the Si(CH 3 ) 3 group has the transport parameters similar to those of poly(trimethylsilyl norbornene) studied earlier. On the other hand, PNB bearing two Si(CH 3 ) 3 groups in each repeat unit reveals much greater gas permeability induced mainly by increased solubility coefficients. The latter result is consistent with the much higher glass transition temperature of this polymer.

Metathesis of silicon-containing olefins

Abstract The behaviour of various olefins containing SiC, GeC, SiSi, SiH, SiOSi and SiOC bonds has been studied in the presence of rhenium on alumina metathesis catalysts. Monovinyl-, allyl-, and butenylsilanes bearing alkyl, alkenyl, aryl, aralkyl, silacycloalkyl, siloxane and hydride substituents, as well as unsaturated silacarbon heterocycles, mono- and diallylgermanes, were used as substrates. Heterogeneous Re 2 O 7 /Al 2 O 3 SnBu 4 and Re 2 O 7 /Al 2 O 3 PbEt 4 catalysts showing good activity in metathesis were examined. Except for hydrides, allyl- and butenylsilanes or germanes were active in metathesis regardless of the nature of the substituents at the metal atom. On the other hand, all of the vinylsilanes used were practically inactive in the reaction. Except for vinyl derivatives, metathesis of di- and polyalkenylsilanes, disilanes, disiloxanes and germanes occurred via both intermolecular and intramolecular pathways. These were used to develop a novel effective synthetic method for producing linear 1,4-bis(triorganylsilyl)- (or germyl-) but-2-enes (including those with ferrocenyl substituents at the silicon) and six-membered mono- and disilacycloalkenes, as well as silaspirane structures. It was shown that α-olefin co-metathesis with allylsilanes (followed by protodesilylation) is a convenient method for increasing the length of an α-olefin hydrocarbon chain.

Effects of cis-trans-configurations of the main chains of poly(trimethylsilyl norbornene) on its transport and sorption properties as well as free volume

Samples of poly(trimetylsilyl norbornene) having different content of cis configurations of double bonds in the main chains were prepared by ring opening metathesis polymerization in the presence of the catalysts characterized by different stereoselectivity (Re2O7, RuCI3, WCI6). It was shown that the polymer obtained in the presence of the WCI6 catalysts having the closest content of the cis-and trans-configurations is distinguished by the largest gas permeability, diffusion, and solubility coefficients. Determination of the parameters of gas sorption isotherms and estimation of free volume using group contribution and positron annihilation methods allowed to conclude that microstructure of this polymer (cis/trans ratio) affects its free volume and, therfore, its transport and thermodynamic properties.

The olefin metathesis reaction : a versatile tool for fine organic synthesis

Abstract This study was devoted to the use of the metathesis reaction for the synthesis of alkenes containing various reactive structural fragments (strained rings, metal-carbon bonds, oxygen-containing functional groups). Among the W, Mo and Re catalysts studied Re2O7/Al2O3PbEt4 and MoCl5/SiO2SnMe4SiCl4 turned out to be the most suitable. They were active toward a wide range of substrates bearing the fragments mentioned above, stable to catalyst poisons and able to be recovered. As a result, we accomplished the metathesis of alkylidene and alkenyl cycloalkanes, including 3- and 4-membered rings, which permitted us to develop a common method of synthesizing bi-and polycyclic hydrocarbons. The co-metathesis of cyclic C5-synthons results in the formation of isoprenoids and terpenoids. On the basis of co-metathesis with allylsilanes, a novel method for the lengthening of α-olefin chains and for double-bond transfer from the α to the β position has been demonstrated. Metathesis and co-metathesis reactions have been used to produce CH3(CH2)mCHCH(CH2)n X (where X = OAc, OH, CHO, m = 0–5, n = 4–10), which are used as insect pheromone components. Synthetic triglycerides formed by a co-metathesis reaction may be used for the production of various vegetable oil analogues.

Synthesis of natural compounds via the cycloolefin cometathesis with α-olefins

Cometathesis of cycloolefins with α-olefins has been studied in the presence of a MoCl 5 /SiO 2 -SnMe 4 catalyst. Three types of polyenes were observed in the products of this reaction: polyenes without any terminal double bond and those having one or two such bonds. It was shown that stereoselectivity of the cometathesis depends on cycloolefin ring size and reaction conditions. In some cases, the content of cis-isomers of I, A-dienes in final mixture reached 63-70%. The obtained polyenes were functionalized via a selective hydroboration of terminal double bonds. A technologically prospective strategy has been developed for the preparation of great variety of natural biologically active compounds (insect sex pheromones, growth regulators, fragrant composition components) on the basis of the cometathesis and hydroboration.

Synthesis of monoene pheromone components having a double bond in positions 6–11 using cometathesis of cycloolefins with α-olefins

Abstract Cometathesis of cycloolefins, 1, with linearα-alkenes, 2, using molybdenum pentachloride catalyst with a cocatalyst of tetramethyltin followed by hydroboration of the resulting α,ω-dienes 3 with 9-borabicyclo [3.3.1] nonane (9-BBN) and oxidation or carbonylation of the resulting boranes, 4, is a convenient route to Δ6–11 monoolefin derivatives.

Synthesis of norbornene–cyclooctene copolymers by the cross-metathesis of polynorbornene with polyoctenamer

Copolymers of norbornene and cyclooctene were synthesized for the first time by the cross-metathesis of polynorbornene with polyoctenamer. This strategy made it possible to use the 1st generation Grubbs catalyst, which exhibits low activity toward copolymerization of those monomers. Statistical multiblock copolymers with average block lengths varying from 200 to 2 units were obtained.

New quadricyclane-based cyclic polycarbosilanes

49 Previously, we showed that silicon-substituted norbornenes and norbornadienes can be widely used for synthesizing macromolecular structures with regularly changed substituents with the aim of revealing theoretically and practically important structure– property relationships [1]. It turned out that polynorbornenes containing trimethylsilyl side groups have good gas transport properties and can serve as efficient membrane materials [2]. We showed that it is precisely Me 3 Si substituents that are responsible for the gas-separation properties and an increase in their number in the monomeric unit enhances the permeability coefficients of polymers. When studying the synthesis of polycarbosilanes of this type, we demonstrated that norbornene and norbornadiene with two SiMe 3 substituents, being active monomers in metathesis polymerization, are almost not polymerized by the addition (vinyl) scheme (Scheme 1). An analogous problem for fluoro-substituted norbornenes was described in [3]. Scheme 1. In the present paper, we describe a new efficient approach to the synthesis of Me 3 Si-substituted norbornenes capable of polymerizing not only by the metathesis mechanism but also by the addition one. This approach involves removal of bulky Me 3 Si substituents from the double bond responsible for polymerization due to the synthesis of 3,4-bis(trimethylsilyl)tricyclo[4.2.1.0 2,5 ]non-7-ene. This compound was synthesized by a reaction that had not been described in organosilicon chemistry, namely, by the reaction of quadricyclane with the corresponding organochlorosilane, trans -1,2-bis(trichlorosilyl)ethylene, and subsequent methylation of the resulting chlorosilyltricyclononene (Scheme 2). Me3Si SiMe3

Comparative Reactivity of Me 3 Si-substituted Norbornene Derivatives in Ring-Opening Metathesis Polymerization

Silyl substituted norbornenes and their derivatives are effective monomers in the synthesis of new prospective polymer materials for gas separation membranes by metathesis and addition polymerization. Comparative activity of norbornenes (NB), norbornadienes (NBD) and tricyclononenes (TCN) with different spatial arrangement of one or two Me3Si substituents in ring-opening metathesis polymerization (ROMP) in the presence of Grubbs initiator Cl2(PCy3)2Ru =CHPh were studied by NMR and GC. It was shown that the rate of the initiation was lower than the propagation for all monomers and the highest activity was inherent to the exo-5-trimethylsilylnorbornene (5-NBSi) and 3-trimethylsilyltricyclononene (3-TCNSi). Disubstituted TCN turned out to be more active than NB having the same number and position of the substituents. The latter were more active than the corresponding NBD. It was found that syn- and anti-isomers of 3-TCNSi polymerized with close rates in contrast to exo- and endo-substituted 5-NBSi, for which polymerization rates were substantially different. Special behavior of monomers with bulky substituents in the geminal position was observed: 5,5-NBSi2 was inactive in the presence of the 1st generation Grubbs initiator, whereas it was polymerized in the presence of the 2nd generation one. Quantum-chemical calculations were in agreement with experimental data and evidenced the influence of energy, electronic and structural properties of the norbornene-type monomers studied on their activity in ROMP.

Modification of silicon-substituted polynorbornenes by epoxidation of main chain double bonds

Postpolymerization modification of metathesis Si-containing polynorbornenes by epoxidation of double bonds of the main chain was carried out for the first time. New polynorbornenes containing one or two side Me3Si substituents in a monomer unit and oxirane fragments in the main chain were obtained and characterized. Some features of epoxidation of polynorbornenes by 1.1-dimethyldioxirane (formed in situ) or m-chloroperbenzoic acid were studied. It was shown that m-chloroperbenzoic acid was an effective epoxidation agent, which did not affect Si−C bonds in polynorbornenes. It was found that the preparation of high-molecular-weight epoxidated polynorbornenes required one to introduce an oxidation inhibitor into the reaction mixture and to perform the reaction in toluene. Chlorine-containing solvents, such as chloroform and chlorobenzene, promoted the destruction of polynorbornenes. It was shown that the introduction of oxirane fragments into the polynorbornene main chain increased its Tg by 15−40°C.