E. B. Portnykh

Ring-opening metathesis polymerization of substituted norbornenes

Abstract Ring-opening metathesis polymerization of a series of substituted norbornenes was carried out. Special attention was paid to the polymerization of monomers bearing silicon-containing groups, e.g., trimethylsilylnorbornene. Various heterogeneous and homogeneous tungsten-, rhenium- and ruthenium-based systems were used as catalysts. It was possible to obtain polymers of some norbornenes having reactive SiCl and SiOR bonds as well as groups capable of polymerizing via different mechanisms. The latter remained unchanged during the ring-opening of the norbornenes and could be used for the further modification of these polymers. Some data on the polymerization of various cycloolefin pairs are presented. It was found that some of the new silicon-containing polynorbornenes belong to the group of the most permeable and rather permselective polymers.

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.

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 silicon-carbon spiranes by metathesis on an aluminumrhenium catalyst

Dialkenyl derivatives of i-silacyclobutane and 1-silacyclopent-3-ene with double bonds β- and γ- to the silicon atom undergo metathesis over an aluminumrhenium catalyst to give silaspirocyclic compounds and open-chain organosilicon trienes containing the silacyclobutane and silacyclopentene fragments. Metathesis of allylbutenyl derivatives of silacyclobutane and silacyclopentene provides a convenient synthetic route to 4-silaspiro[3,5]non-6-enes and 5-silaspiro[4,5]deca-2,7-dienes.

Metathesis of dialkenylsilanes and polymerization of 1,1-dimethyl-1-sila-3-cyclopentene in presence of aluminum-rhenium catalysts

Conclusions1.It was shown that the efficient metathesis of dialkenylsilanes of variable structure in the presence of aluminum-rhenium catalysts is possible.2.Conditions were found for the preparative synthesis of 4,9-disila-4,4,9,9-tetramethy1-1,6,11-dodecatriene and 1,1-dimethyl-1-sila-3-cyclohexene via the inter- and intramolecular metathesis reaction.3.1,1-Dimethyl-1-sila-3-cyclopentene polymerizes to a linear polysilapentenomer in the presence of Al-Re catalysts.

Preparation of silyl derivatives of unsaturated carbocyclic compounds by the Diels-Alder reaction of 1,2-dimethylenecyclobutane and vinylsilanes

The Diels-Alder reactions of 1,2-dimethylenecyclobutane with vinyltrichlorosilane and vinylmethyldichlorosilane give the corresponding trichlorosilyl and methyldichlorosilyl derivatives of cyclobutene. Methylation of these derivatives gave 4-trimethylsilylbicyclo[4.2.0]oct-1-ene, which underwent thermal isomerization to 4-trimethylsilyl-1,2-dimethylcyclohexane.

Extension of the hydrocarbon chains of ?-olefins by their cometathetical reaction with trimethylallylsilane

ConclusionsBy cometathesis of α-olefins with allylsilanes and subsequent desilanization of the products obtained, the lengthening of the hydrocarbon chain of α-olefins has been achieved.

Synthesis of Cyclobutane Hydrocarbons By Combination of (2+2)π-Cycloaddition and Olefin Metathesis. Their Abilities as Effective Propellants

Chemistry of cyclobutane hydrocarbons and their derivatives has been a subject of scientific attention science the beginning of the last century up to present time. The reasons of such a long attention is in special features of highly strained 4-membered ring structure and peculiar reactivity of cyclobutane compounds [1]. In application sense the compounds of this type demonstrate a range of interesting properties such as biological activity [2,3], capability to store energy [4,5], monomers activity to polymerization [1], etc. They are used as insecticides, in particular insect pheromone components [2,3], highly effective propellants [4.5] and energy accumulators [6].

METATHESIS REACTIONS OF ALLYLSILANES CONTAINING BULKY AROMATIC SUBSTITUENTS

Bulky substituents, such as α-naphthyl and ferrocenyl groups, do not inhibit the metathesis of allylsilanes on a Re2O7/Al2O3-SnBu4, catalyst system. Metathesis represents a preparative synthetic method for the synthesis of 1,4-bis(α-napthyl-dimethylsilyl)- and 1,4-bis(ferrocenyldimethylsilyl)but-2-enes.

Metathesis of alkenylgermanes on a rhenium oxide catalyst

ConclusionsFeasibility was demonstrated for the metathesis of dimethyldiallylgermane on a rhenium oxide/alumina catalyst with the formation of dimethylgermacyclopentene and a linear product, 4,4,9,9-tetramethyl-4, 9-digerma-1,6,11-dodecatriene. The metathesis of trimethylallylgermane leads to the quantitative preparation of 2,2,7,7-tetramethyl-2,7-digerma-4-octene.