Poly -tartrate

Canali et al.17 reported the use a linear poly(tartrate) ligand in the asymmetric epoxidation of allylic alcohols. Moderate results were obtained. They also reported the use of branched/crosslinked poly(tartrate), which gave moderate to good results in the asymmetric epoxidation of allylic alcohols. As shown in Scheme 4-9, when L-(+)-tartaric acid and 1,8-octanediol are heated... 

Figure 5.3 Oxidation of some (Z)-allylic alcohols and some homoallylic alcohols using poly(tartrate).

Alkene Epoxide Poly(tartrate) % branching Molar ratio alkene Ti tartrate Temperature (°C) Time Isolateda Yield (%) Ee(%)... 

One of the first attempts to extend polymer-assisted epoxidations to asymmetric variants were disclosed by Sherrington et al. The group employed chiral poly(tartrate ester) hgands in Sharpless epoxidations utilizing Ti(OiPr)4 and tBuOOH. However, yields and degree of stereoselection were only moderate [76]. In contrast to most concepts, Pu and coworkers applied chiral polymers, namely polymeric binaphthyl zinc to effect the asymmetric epoxidation of a,/9-unsaturated ketones in the presence of terPbutyl hydroperoxide (Scheme 4.11). 

A polymer-supported Sharpless epoxidation catalyst was prepared using linear poly(tartrate ester) catalyst ligands 43.65 This catalyst system was used in the reaction of tranA-hex-2-en- l-ol with titanium tc/ra-isopropoxide and tert-butyl hydroperoxide to afford the desired epoxide in high chemical yield and moderate enantiomeric excess. 

Recently, the use of polymer-supported chiral ligands and poly(amino acids) as enantioselective elicitors during epoxidation has become popular. Thus, poly(tartrate ester) is for the Sharpless asymmetric epoxidation,poly-L-leucine for epoxidation of enones. 

The asymmetric epoxidation of functionalized alkenes still attracts considerable attention. Synthetic chemists continue to be in search of new and improved routes to epoxides, since they provide versatile intermediates for natural product synthesis. The topic of preparative techniques for chiral epoxides is seldom broached without the mention of the Sharpless epoxidation. Indeed, the impact of this protocol cannot be overestimated, as new applications continue to be reported. For example, linear poly(tartrate ester) ligands have been used this past year to generate a solid-supported Sharpless-type catalyst <97CC123>. 

Condensation polymerization of glycols with tartaric acid results in poly(alkylene tartrate)s [42 4]. The hydroxylated polyesters from C2 and C4 are hydrophilic and water soluble and those from C6 and higher glycol are water insoluble with increase in hydrophobicity with increasing size of glycols. Crosslinkable unsaturated poly(alkylene tartrate)s are obtained by adding maleic anhydride to the polymerization of glycols with tartaric acid (4) [45]. Poly(tartrate) was obtained from the condensation of tartaric acid ketal with tartaric acid diacetate [46]. 

Table 5-1. Enantioselectivities determined for several drugs. All experiments were performed at room temperature, except those marked with, which were performed at 4 °C. In some cases a lipophilic anion was used to facilitate the solubilization of the drug in the organic phases (PFj = hexafluorophosphate BPh = tetraphenyl borate). DHT = dihexyl tartrate DBT = dibenzoyl tartrate PLA = poly (lactic acid). ...

ASYMMETRIC EPOXIDATION OF ( >UNDEC-2-EN-l-OL USING POLY(OCTAMETHYLENE TARTRATE)... 

The solid was recovered by decanting off the solvents and the polymer dried under vacuum at 40 °C for 6 hours and at room temperature for 2 days to yield 16.6 g (95%) of poly(octamethylene tartrate) (3). 

Poly(octamethylene tartrate) can be used directly in place of dialkyl tartrates in the Sharpless epoxidation of allylic alcohols. 

Use of poly(octamethylene tartrate) in place of dialkyl tartrates offers practical utility since the branched polymers yield hetereogeneous Ti complex catalysts which can be removed by filtration. Overall the work-up procedure is considerably simplified relative to the conventional Sharpless system. In addition, significant induction is shown in the epoxidation of (Z)-allylic alcohols[7] and even with homoallylic[8] species where the dialkyltartrates give very poor results Figure 5.3. Table 5.2 is illustrative of the scope using the polymer ligand. 

Table 5.2 Asymmetric epoxidation of cis- and trans-allylic and homoallylic alcohols using poly(octamethylene tartrate)/Ti(Oz Pr)4/TBHP. 

Poly(dodecamethylene D-tartrate) (G) was prepared by melt polymerization of 1,12-dodecanediol and tartaric acid with p-to-luenesulfonic acid as catalyst. (5)... 

Investigation of template poly condensation kinetics has only been studied within a very narrow scope. Polymerization of dimethyl tartrate with hexamethylene diamine was found to be enhanced by using as a template poly(vinyl pyrrolidone), poly(2-vinyl pyridine), or polysaccharides and poly(vinyl alcohol), poly(4-vinyl pyridine). In this case, the template can be treated as a catalyst. No information exists on the influence of the template on the order of reaction. The increase in molecular weight of the polymerization product by the template can be induced by a shift of equilibrium or by an increase in the reaction rate. A similar increase in the reaction rate was observed when poly(4-vi-nyl pyridine) was used in the synthesis of poly(terephtalamides) activated by triphenyl phosphite.The authors suggested that a high molecular weight template was involved in the increase of the local concentration of the substrate (terephthalic acid) by adsorption and activation via N-phosphonium salt of poly(4- vinyl pyridine). 

The photodegradation of drug A formulation solutions at a fixed iron content was also examined for a series of 10 mM poly- and monocarboxylate buffers (oxalate, succinate, maleate, tartrate, and formate). The general photocatalysis was observed for all systems examined and varied from 0.40% to 17.6% loss of drug A for solutions containing 50ppb iron (Table 11). 

Poly(ethylacrylate methyl methacrylate) (Eudragit) Metoprolol tartrate [117]... 

Figure 1.13 GC analysis of organic acid methyl esters in a) standard solution, b) Chardonnay wine, c) Asti sparkling wine. 1. methyl lactate, 2. dimethyl succinate, 3. dimethyl maleate (i.s.), 4. dimethyl malate, 5. dimethyl tartrate, 6. trimethyl citrate. Chromatographic conditions poly(ethylene) glycol fused silica capillary column (30m x 0,25mm 0.25 xm), injector and detector temperature 250°C, flame ionization detector. Oven program 2min at 50 °C, from 50 to 200 °C at rate 4°C/min, 200°C isotherm for lOmin (Di Stefano and Bruno, 1983)...

A heterogeneous version of the Sharpless [73] epoxidation of allylic alcohols has been described [74], A complex formed between Ti(OPr )4 and a linear poly-L-tar-trate, in combination with zeolite 4A as a drying agent, catalyzed the enantio-selective epoxidation of tra/iJ-2-hexen-l-ol with TBHP (92 % yield and 79 % ee), although not all of the titanium remained complexed to the polymer on recycling and was uncomplexed or complexed with tartrate monomer/oligomer in solution. 

Fig. 6. Scanning electron micrograph of a poly(acryl amide) gel templated in a lyotropic mesophase of CTMA-tartrate. The formation of a layer-like morphology is directed by the anisotropic reaction medium. Adapted with permission from [52]...

Table I. Extent of Growth of A. Niger on Poly(alkylene D-tartrates) after 14 Days at 37°C...

We found that the polyurethane obtained by reacting poly(do-decamethylene D-tartrate) with 1,6-di-isocyanatohexane supported the growth of A. niger with an ASTM rating of 4 (16). A similar polyurethane derived from poly(hexamethylene tartrate) was degraded in vivo... 

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