Abstract:
An alkylative cycloaddition method is provided that is particularly useful for the synthesis of many of the Vitamin D analogues with differing side chains. Thus, a preferred synthesis is of Vitamin D analogues having a side chain R.sub.1 where a substantially geometrically pure first precursor having the structure ##STR1## and a second precursor are provided, the second precursor being a 1,7 enyne. These precursors are reacted in the presence of a palladium catalyst to form compounds having the structure ##STR2## where R.sub.2 hydrogen, hydroxyl, lower alkoxy, fluorine, or a protecting group, and R.sub.3 is hydrogen, hydroxyl, lower alkoxy, fluorine, or a protecting group.
Abstract:
The present disclosure relates to a novel method, expression vectors, and host cells for producing abienol by converting geranylgeranyl diphosphate (GGPP) to abienol in the presence of a combination of a class II diterpene synthase and a bifunctional class I/II abienol synthase.
Abstract:
Compound of formula ##STR1## wherein a) indexes m and n are identical and stand each for an integer number equal to zero, symbols R.sup.1 and R.sup.2 are identical and represent each a hydrogen atom, or are different and represent each a hydrogen atom or a methyl radical, symbols R.sup.5 and R.sup.8 stand each for a methyl radical, symbols R.sup.6 and R.sup.7 can be identical or different and designate each a hydrogen atom or a methyl radical and, either symbol R.sup.4 represents a methyl radical and symbol R.sup.3 stands for a hydrogen atom or a methyl radical, or symbols R.sup.3 and R.sup.4 represent each a methylene radical belonging to a ring such as indicated by the dotted line, with the proviso that the following combinations are excluded:1. R.sup.1 =R.sup.2 =R.sup.3 =R.sup.6 =R.sup.7 =H, or2. R.sup.1 =R.sup.2 =R.sup.3 =H and R.sup.6 or R.sup.7 =CH.sub.3, or3. R.sup.2 =CH.sub.3 and R.sup.3 =R.sup.6 =R.sup.7 =H, or4. R.sup.2 =CH.sub.3 and R.sup.3 =H and R.sup.6 or R.sup.7 =CH.sub.3, or5. R.sup.1 =R.sup.3 =CH.sub.3, or6. R.sup.3 =R.sup.4 =CH.sub.2 and R.sup.2 or R.sup.7 =CH.sub.3 ; or whereinb) indexes m and n are different and define each an integer number equal to 0 or 1, symbol R.sup.2 stands for a hydrogen atom or a methyl radical, symbols R.sup.1 and R.sup.3 designate each a hydrogen atom, symbol R.sup.4 represents a methyl radical and, either symbols R.sup.5 and R.sup.6 are identical (n=1) and represent each a methylene radical belonging to a ring such as indicated by the dotted line, R.sup.7 representing a hydrogen atom and R.sup.8 a methyl radical, or symbol R.sup.5 stands for a methyl radical and symbol R.sup.6 for a hydrogen atom, R.sup.7 and R.sup.8 being then identical (m=1) and designating each a methylene radical belonging to a ring such as indicated by the dotted line;or any mixture of two or more structural isomers of formula (I).Compounds (I) develop odor notes of the musky type and can therefore be used as active ingredients in perfuming compositions and perfumed articles of varied nature.A process for the preparation of compounds (I) is described.
Abstract:
A process comprising reacting a 2-indenylboranic acid (ester) with a bromosubstituted compound in the presence of the Pd catalyst bis(triphenylphosphin)palladium dichloride and a base to form the corresponding bridged bis(indenyl) ligand. Where the 2-indenylboranic acid (ester) is the pinacolester of 2-indenylboranic acid, the process may further comprise reacting a 2-bromo indene compound with pinacolborane in the presence of a Pd catalyst and a base to form the corresponding 2-indenylpinacolylborane compound. Bridged bis(indenyl)ligands may suitably be used in the preparation of metallocene complexes, such as 2,2′-bis(2-indenyl)biphenyl ZrCl2 and 1,2-bis (2-indenyl)benzene ZrCl2. These metallocene complexes may be used for the polymerization, optionally in the presence of a cocatalyst, of one or more α-olefins, preferably for the polymerization of ethylene.
Abstract:
A catalyst active in the (co)polymerization of .alpha.-olefins is obtained by putting the following components in contact with each other: (i) a "bridged" bis-metallocene derivative of a metal M selected from titanium, zirconium or hafnium, wherein the divalent "bridge" has a rigid structure linked to two .eta..sup.5 -cyclopentadienyl ring with two methylene groups having a distance from each other of less than 3.5 .ANG.;(ii) a co-catalyst consisting of an organic derivative of a metal M' selected from boron, aluminium, gallium and tin. Such a catalyst allows high polymerization rates to be reached and is particularly suitable for high temperature polymerization process and co-polymerization of ethylene with other .alpha.-olefins.
Abstract:
An aromatic hydrocarbon in which at least one hydrogen atom on the ring is substituted by a group selected from the class consisting of unsubstituted or lower alkyl-substituted tricyclo[5.2.1.0.sup.2,6 ]dec-3-yl, tricyclo[5.2.1.0.sup.2,6 ]dec-4-yl, tetracyclo[6.2.1.1.sup.3,6.0.sup.2,7 ]dodec-4-yl and tetracyclo[6.2.1.1.sup.3,6.0.sup.2,7 ]dodec-5-yl groups, or its hydrogenation product.The compound is prepared by reacting an aromatic hydrocarbon having at least one hydrogen atom on the ring with a compound selected from the group consisting of unsubstituted or lower alkyl-substituted tricyclo[5.2.1.0.sup.2,6 ]dec-3-ene and tetracyclo[6.2.1.1.sup.3,6.0.sup.2,7 ]dodec-4-ene in the presence of a Friedel-Crafts catalyst, or hydrogenating the thus-obtained compound in the presence of a hydrogenation catalyst.The compound is useful as an additive for adhesives.
Abstract:
Preparation of alkylidenecyclobutane derivatives and of cyclobutene derivatives by contacting a (cyclo)alkene with an allene or with a 1-alkyne in the liquid phase in the presence of a dissolved Lewis acid derived from an element of Group III A of the Periodic Table of the Elements, titanium, tin, antimony, tantalum, rhenium, iron, or zinc.
Abstract:
A ligand of formula (I′) wherein L is a divalent bridge selected from —R′2C—, —R′2C—CR′2—, —R′2Si—, —R′2Si—SiR′2—, —R′2Ge—, wherein each R′ is independently a hydrogen atom, C1-20-hydrocarbyl, tri(C1-20-alkyl)silyl, C6-20-aryl, C7-20-arylalkyl or C7-20-alkylaryl; R2 and R2′ are each independently a C1-20 hydrocarbyl radical; R5′ is a C1-20 hydrocarbyl group; R6, R6′, R7 and R7′ are each independently hydrogen or a C1-20 hydrocarbyl group; Ar and Ar′ are independently an aryl or heteroaryl group having up to 20 carbon atoms; each R1 is a C1-20 hydrocarbyl group or two R1 groups on adjacent carbon atoms taken together can form a fused 5 or 6 membered non aromatic ring with the Ar group; and each R4 is a C1-20 hydrocarbyl group; and the dotted lines represent a double bond present in between carbons 1 and 2 or 2 and 3 of the indenyl ring.
Abstract:
A 3,3′,4,4′-tetraalkyl cyclohexylbenzene represented by the general formula (1): in which R represents an alkyl group having 1 to 4 carbon atoms, which may be easily converted into a 3,3′,4,4′-biphenyltetracarboxylic acid and a 3,3′,4,4′-biphenyltetracarboxylic dianhydride thereof, which are starting materials for a polyimide, via a 3,3′,4,4′-tetraalkylbiphenyl; and a method for producing the same.
Abstract:
The present invention relates to a photoreactive polymer that comprises a multi-cyclic compound in a main chain, and a polymerization method thereof. Since the photoreactive polymer according to the present invention comprises a multi-cyclic compound having a high glass transition temperature as a main chain, the thermal stability is excellent, and since the mobility of the main chain is relatively high as compared to that of an additional polymer, a photoreactive group can be freely moved in the main chain of the polymer. Accordingly, it is possible to overcome a slow photoreactive rate that is considered a disadvantage of a polymer material used to prepare an alignment film for known liquid crystal display devices.