Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1997-10-28
2001-04-03
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C525S417000, C525S902000
Reexamination Certificate
active
06211316
ABSTRACT:
This invention relates to dendrimers of TADDOLs, in particular dendrimers of &agr;,&agr;,&agr;′,&agr;′-tetraaryl-1,2-dioxolane-dimethanol, titanium (IV) salts thereof and the use of polymer-bound dendrimer Ti-salts thereof in syntheses involving carbon-carbon bond formation, in particular the catalytic addition of diethylzinc to aldelydes.
It is known to incorporate TADDOL into a crosslinked (divinylbenzene) polystyrene polymer and use the corresponding titanate in addition reactions of diethyl zinc to aldelydes. The known polymer-bound TADDOLs are characterised in that the TADDOL moiety depends from the polystyrene chain through the dioxolane group of said TADDOL.
The polymer-bound TADDOLs are heterogeneous catalysts and are therefore more easily removed from a reaction mixture than a free TADDOL which is homogeneous with a reaction mixture. However, known polymer-bound titanium salts of TADDOLs are less effective than said free titanium salts of TADDOLs at catalysing the aforementioned reactions. There remains a need to provide a polymer-bound TADDOL, the TADDOLate of which is more reactive than the known polymer-bound TADDOLates.
Surprisingly it has now been found that a dendrimer TADDOLate bound to a polymer is more active as a catalyst in carbon-carbon bond-forming reactions, in particular in the catalytic reaction of diethylzinc to aldehydes, than the known polymer-bound TADDOlates.
Accordingly, the invention provides in one of its aspects a dendrimer TADDOL.
TADDOLs and the syntheses for forming same are known in the art see, for example
Helvetica Chim. Acta,
77, 2071-2110, (1994) which is incorporated herein by reference. TADDOLs of the present invention may be any of those known in the art, in particular 2-mono- or 2,2-disubstituted at the 1,3-dioxolane group. Substituents at the 2-position may be optionally substituted alkyl, e.g. methyl or ethyl, and optionally substituted phenyl or naphthyl. Said substituents may be substituted with, for example halogen, e.g. Cl Br or F, OH or alkoxy. When the 1,3-dioxolane group is 2,2-disubstituted it is preferably 2,2-dialkyl substituted, more particularly 2,2-dimethyl substituted.
The aryl groups of the preferred TADDOLs may be phenyl, substituted phenyl, naphthyl or substituted naphthyl. Insofar as the aryl groups are substituted, they may be identically or differently substituted.
Dendrimers are known in the art, see for example D. A. Tomalia et. al. Angew. Chem. (1990), 102, 119 and N. Ardoin et. al. Bull. Soc. Chem. Fr. 1995, 132, 875-909 which are incorporated herein by reference. By dendrimer of TADDOL or TADDOLate is meant a macromolecule comprising a central core formed by the aforementioned TADDOL or TADDOLate moiety and depending radially from said core (ususally branched) substituents.
There are many types of dendritic substituents known in the art (see the aforementioned references). Any of the known dendritic substituents may be employed as substituents in the present invention provided that they are unreactive with respect to the reagents used in the catalytic syntheses or do not otherwise interfere with the catalytic effect of the TADDOlate core, for example by sterically crowding the TADDOLate core.
Dendritic substituents may be characterised by their degree of branching. A dendritic substituent may, in fact, not have any branch points in which case it is referred to as a zero (0) generation substituent. More typically however, dendritic substituents have one (first generation), two (second generation) or more branch points, for example up to 10 branch points. Preferred dendritic substituents are one to three generation number substituents, more particularly two or three generation number substituents.
As examples of dendritic substituents there may be mentioned those based on branched hydrocarbon chains, i.e. alkyl or aryl chains, polyethers, e.g. alkyl ethers, aryl ethers or aryl-alkyl ethers, thio ethers or polyamides. Most preferred dendritic substituents are based on dihydroxybenzylbromide, in particular 3,5-dihydroxybenzylbromide, the branched substituent thereby being created using an iterative synthetic process of reacting said benzyl bromide moiety of one molecule with the hydroxy substituents of another molecule until a substituent of the desired generation number is obtained.
Dendrimers according to the invention may bear terminal functional groups which can react with appropriate functionality of a polymer (or a monomer unit thereof) in order to bind said dendrimer to a polymer support.
Preferably said functionality is an unsaturated group, more preferably an alkene group, e.g. vinyl group or a styryl group. The terminal functional groups may be connected to the dendrimer chain according to known processes, for example as an end-capping step as part of the iterative process discussed above.
Preferred dendrimer TADDOLs have only one dendritic substituent attached to each aryl group. the dendritic substituents may be connected to the aryl groups by a carbon-carbon bond or a carbon-heteroatom bond, e.g. carbon-oxygen, carbon-nitrogen or carbon-sulphur bond. Preferably the dendritic substituents are attached to the aryl groups through a carbon-oxygen bond.
Dendritic substituents useful in the invention may be made according to syntheses known in the art (see the aforementioned references which are incorporated herein by reference).
The invention provides in another of its aspects a dendrimer of &agr;,&agr;,&agr;′,&agr;′-tetraaryl-1,3-dioxolane-4,5-dimethanolate of titanium (IV) hereinafter referred to as a dendrimer TADDOLate.
The source of titanium (IV) may be any of the known alkyl, aryl or alkoxy titanium complexes known in the art. A preferred source of titanium (IV) are tetra alkoxy titanates, more particularly tetraisopropyloxy titanate. TADDOLates may be 1:1 complexes, that is one TADDOL ligand complexed to one titanium atom, or a 2:1 complex wherein two TADDOL ligands are complexed with one titanium atom. 1:1 TADDOLates are preferred. A more preferred titanium TADDOLate is the diisopropoxy-Ti-TADDOLate.
The insertion of the Ti atom into the TADDOL core may be carried out according to known syntheses. Preferred reaction conditions for forming a TADDOL-titanate are described in Tetrahedron 50 4363-4384 (1984) which is incorporated herein by reference.
A more preferred dendrimer TADDOLate has dendritic substituents based on dihydroxybenzylbromide, in particular 3,5-dihydroxybenzylbromide. More preferably the TADDOLate is a 2- or 3-generation number dendrimer, in particular, being terminally substituted with an unsaturated group, e.g a vinyl group or a styryl group. The most preferred dendrimer TADDOLate are the preferred dendrimers aforementioned with one dendritic substituent attached to each aryl group of the TADDOLate core.
In another aspect of the invention there is provided a polymer cross-linked with a TADDOL or TADDOLate as hereinabove described.
Polymers according to the invention may be made up of any suitable monomeric units at least some of which will react with the terminal unsaturated groups of the dendritically substituted TADDOLs or TADDOLates. The terminal unsaturation of the dendrimers may react with other said monomeric units in a copolymerisation reaction thereby becoming incorporated into the polymer chain. Alternatively, the terminal unsaturation may react with functionality depending from said other monomeric units or a polymer formed from said monomeric units thereby forming chains depending from the polymer or copolymer backbone. However the terminal unsaturation reacts with the respective monomeric units or polymers formed therefrom, when two or more of the dendritic substituents bearing terminal unsaturated units of the dendrimer TADDOL interact with the polymer the dendrimer essentially acts as a crosslinker for the polymer.
Preferably the unsaturated terminal groups of the dendrimer TADDOL take part in a copolymerisation with styrene. The polymerisation reaction may be carried out according to known synthetic methods. The amount of dendrimer TAD
Novartis AG
Wildman David E.
Wu David W.
Zalukaeva Tanya
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