- Rapid Organocatalytic Formation of Carbon Monoxide: Application towards Carbonylative Cross Couplings
-
Herein, the first organocatalytic method for the transformation of non-derivatized formic acid into carbon monoxide (CO) is introduced. Formylpyrrolidine (FPyr) and trichlorotriazine (TCT), which is a cost-efficient commodity chemical, enable this decarbonylation. Utilization of dimethylformamide (DMF) as solvent and catalyst even allows for a rapid CO generation at room temperature. Application towards four different carbonylative cross coupling protocols demonstrates the high synthetic utility and versatility of the new approach. Remarkably, this also comprehends a carbonylative Sonogashira reaction at room temperature employing intrinsically difficult electron-deficient aryl iodides. Commercial 13C-enriched formic acid facilitates the production of radiolabeled compounds as exemplified by the pharmaceutical Moclobemide. Finally, comparative experiments verified that the present method is highly superior to other protocols for the activation of carboxylic acids.
- Zoller, Ben,Zapp, Josef,Huy, Peter H.
-
supporting information
p. 9632 - 9638
(2020/07/13)
-
- Chemoselective Nucleophilic Functionalizations of Aromatic Aldehydes and Acetals via Pyridinium Salt Intermediates
-
The development of a novel chemoselective functionalization can diversify the strategy for synthesizing the target molecules. The perfect chemoselectivity between aromatic and aliphatic aldehydes is difficult to achieve by the previous methods. The aromatic aldehyde-selective nucleophilic addition in the presence of aliphatic aldehydes was newly accomplished. Namely, the aromatic aldehyde-selective nucleophilic addition using arenes and allyl silanes proceeded in the presence of trialkylsilyl triflate and 2,2′-bipyridyl, while the aliphatic aldehydes completely remained unchanged. The reactive pyridinium-type salt intermediate derived from an aromatic aldehyde chemoselectively underwent the nucleophilic substitution. Moreover, the aromatic acetals as the protected aldehydes could be directly transformed into similar pyridinium salt intermediates, which reacted with various nucleophiles coexisting with the aliphatic aldehydes.
- Kawajiri, Takahiro,Kato, Maho,Nakata, Hiroki,Goto, Ryota,Aibara, Shin-Yo,Ohta, Reiya,Fujioka, Hiromichi,Sajiki, Hironao,Sawama, Yoshinari
-
p. 3853 - 3870
(2019/03/07)
-
- Silver-Catalyzed Olefination of Acetals and Ketals with Diazoesters to β-Alkoxyacrylates
-
The first silver-catalyzed reaction of acetals or ketals with diazoesters leading to trisubstituted or tetrasubstituted β-alkoxyacrylates is now reported. A broad range of acetals and ketals bearing different substituents is compatible with this protocol and thus provides an attractive approach for the synthesis of complex β-alkoxyacrylates. The power of this method was further demonstrated by the successful synthesis of picoxystrobin, which is one of the most popular agricultural fungicides commercialized by Dupont.
- Li, Jiawen,Qian, Bo,Huang, Hanmin
-
supporting information
p. 7090 - 7094
(2018/11/23)
-
- Synthesis of 4-(Dibromomethyl)benzaldehyde by Catalytic Debromophosphoryl- and Phosphonyloxylation of 1,4-Bis(dibromomethyl)benzene with Phosphorus(IV) Acid Methyl Esters and Its Properties
-
A new procedure has been developed for the simultaneous preparation of terephthalaldehyde and 4-(dibromomethyl)benzaldehyde by catalytic debromophosphoryl- and phosphonyloxylation of 1,4-bis- (dibromomethyl)benzene with P(IV) acid methyl esters. The reaction of 4-(dibromomethyl)benzaldehyde with ortho esters in the presence of sulfuric acid gave the corresponding acetals, whereas in the presence of ZnCl2 terephthalaldehyde bis-acetals were formed. 4-(Dibromomethyl)benzaldehyde and its acetal were converted to methyl 4-(dibromomethyl)- and 4-(dimethoxymethyl)benzoates which were phosphorylated by the action of chlorophosphines, as well as by successive treatment with phosphorus(III) chloride and P(III) esters.
- Gazizov,Ivanova, S. Yu.,Khairullin,Kirillina, Yu. S.,Gazizova
-
p. 2243 - 2250
(2019/01/04)
-
- Synthesis of aromatic aldehyde acetals from (dibromomethyl)arenes
-
Zinc chloride-catalyzed double debromoalkoxylation of (dibromomethyl)arenes on treatment with trialkyl orthoformates resulted in the corresponding aromatic aldehyde acetals. On the first step, α-brominated ether is formed, which undergoes the second debro
- Gazizov,Ivanova, S. Yu.,Bashkirtseva, N. Yu.,Khairullina,Khairullin,Gazizova
-
p. 1230 - 1233
(2017/12/02)
-
- Chitosan-acrylic polymeric nanoparticles with dynamic covalent bonds. Synthesis and stimuli behavior
-
Drug delivery represents one of the most important research fields within the pharmaceutical industry. Different strategies are reported every day in a dynamic search for carriers with the ability to transport drugs across the body, avoiding or decreasing toxic issues and improving therapeutic activity. One of the most interesting strategies currently under research is the development of drug delivery systems sensitive to different stimuli, due to the high potential attributed to the selective delivery of the payload. In this work, a stimuli-sensitive nanocarrier was built with a bifunctional acrylic polymer, linked by imine and disulfide bonds to thiolate chitosan, the latter being a biopolymer widely known in the field of tissue engineering and drug delivery by its biodegradability and biocompatibility. These polymer nanoparticles were exposed to different changes in pH and redox potential, which are environments commonly found inside cancer cells. The results proof the ability of the nanoparticles to keep the original structure when either changes in pH or redox potential were applied individually. However, when both stimuli were applied simultaneously, a disassembly of the nanoparticles was evident. These special characteristics make these nanoparticles suitable nanocarriers with potential for the selective delivery of anticancer drugs.
- Palacio, Herman,Segura-Sánchez, Freimar,Otálvaro, Felipe,Giraldo, Luis Fernando,Ponchel, Gilles
-
p. 1132 - 1143
(2018/05/02)
-
- Chitosan-Acrylic polymeric nanoparticles with dynamic covalent bonds. Synthesis and stimuli behavior
-
Drug delivery represents one of the most important research fields within the pharmaceutical industry. Different strategies are reported every day in a dynamic search for carriers with the ability to transport drugs across the body, avoiding or decreasing toxic issues and improving therapeutic activity. One of the most interesting strategies currently under research is the development of drug delivery systems sensitive to different stimuli, due to the high potential attributed to the selective delivery of the payload. In this work, a stimuli-sensitive nanocarrier was built with a bifunctional acrylic polymer, linked by imine and disulfide bonds to thiolate chitosan, the latter being a biopolymer widely known in the field of tissue engineering and drug delivery by its biodegradability and biocompatibility. These polymer nanoparticles were exposed to different changes in pH and redox potential, which are environments commonly found inside cancer cells. The results proof the ability of the nanoparticles to keep the original structure when either changes in pH or redox potential were applied individually. However, when both stimuli were applied simultaneously, a disassembly of the nanoparticles was evident. These special characteristics make these nanoparticles suitable nanocarriers with potential for the selective delivery of anticancer drugs.
- Palacio, Herman,Otálvaro, Felipe,Giraldo, Luis Fernando,Ponchel, Gilles,Segura-Sánchez, Freimar
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p. 1132 - 1143
(2017/12/26)
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- Regioselective Allylation of Carbon Electrophiles with Alkenyl-silanes under Dual Catalysis by Cationic Platinum(II) Species
-
In the presence of catalytic amounts of platinum(II) chloride and silver(I) hexafluoroantimonate, (Z)-alkenylsilanes reacted with various carbon electrophiles (acetals, aminals, carboxylic anhydrides, alkyl chlorides, etc.) at the γ-position to give allylation products. A plausible mechanism for the platinum-catalyzed allylation involves alkene migration of alkenylsilanes to allylsilanes and subsequent allylation of carbon electrophiles, both of which are catalyzed by a cationic platinum(II) species.
- Kinoshita, Hidenori,Kizu, Ryosuke,Horikoshi, Masahiro,Inoue, Gen,Fujimoto, Masayuki,Saito, Masanori,Ichikawa, Junji,Hosomi, Akira,Miura, Katsukiyo
-
supporting information
p. 520 - 534
(2016/02/16)
-
- Design, Synthesis, and Pharmacological Evaluation of Novel N-Acylhydrazone Derivatives as Potent Histone Deacetylase 6/8 Dual Inhibitors
-
This manuscript describes a novel class of N-acylhydrazone (NAH) derivatives that act as histone deacetylase (HDAC) 6/8 dual inhibitors and were designed from the structure of trichostatin A (1). Para-substituted phenyl-hydroxamic acids presented a more potent inhibition of HDAC6/8 than their meta analogs. In addition, the effect of compounds (E)-4-((2-(4-(dimethylamino)benzoyl)hydrazono)methyl)-N-hydroxybenzamide (3c) and (E)-4-((2-(4-(dimethylamino)benzoyl)-2-methylhydrazono)methyl)-N-hydroxybenzamide (3f) on the acetylation of α-tubulin revealed an increased level of acetylation. These two compounds also affected cell migration, indicating their inhibition of HDAC6. An analysis of the antiproliferative activity of these compounds, which presented the most potent activity, showed that compound 3c induced cell cycle arrest and 3g induced apoptosis through caspase 3/7 activation. These results suggest HDAC6/8 as a potential target of future molecular therapies for cancer.
- Rodrigues, Daniel A.,Ferreira-Silva, Guilherme à.,Ferreira, Ana C. S.,Fernandes, Renan A.,Kwee, Jolie K.,SantAnna, Carlos M. R.,Ionta, Marisa,Fraga, Carlos A. M.
-
p. 655 - 670
(2016/02/05)
-
- A General Access to Propargylic Ethers through Br?nsted Acid Catalyzed Alkynylation of Acetals and Ketals with Trifluoroborates
-
A general Br?nsted acid catalyzed methodology for the alkynylation of acetals and ketals with alkynyltrifluoroborate salts has been developed. The reaction proceeds rapidly to afford valuable synthetic building block propargylic ethers in good to excellent yields. Unlike Lewis acid catalyzed transformations of trifluoroborates, this approach does not proceed via unstable organodifluoroborane intermediate. As a result, the developed methodology features excellent functional group tolerance and good atom economy. Br?nsted acid catalyzed alkynylation of acetals and ketals is described. Alkynyltrifluoroborate salts react rapidly to afford propargylic ethers. Organodifluoroborane, which is a common intermediate in Lewis acid catalyzed reactions of trifluoroborates, has not been observed. The reaction exhibits generally high yields and excellent functional group tolerance.
- Baxter, Matthew,Bolshan, Yuri
-
supporting information
p. 13535 - 13538
(2015/09/22)
-
- Process of isolating methyl-4-formylbenzoate and dimethylterephtalate with high yield
-
The present invention refers to p (p-xylene)-xylene using prepared from the oxidation reaction and the esterification reacted with dimethyl terephthalate from byproduct in the obtained reaction in the production of (DMT), to the temperature of by-product methyl-4-an alcohol (MFB) [...] polyacetal the acids and reaction and then a compounds, an amine acetal compound said DMT removed and by quenching compound, then methyl-4- [...] method separation and recovery of high yield provides. (by machine translation)
- -
-
Paragraph 0061-0064
(2016/11/14)
-
- Templating carbohydrate-functionalised polymer-scaffolded dynamic combinatorial libraries with lectins
-
A conceptually new approach to the design of macromolecular receptors for lectins is outlined. Carbohydrate-functionalised Polymer-Scaffolded Dynamic Combinatorial Libraries (PS-DCLs) have been prepared in aqueous solution by the reversible conjugation of carbohydrates possessing acylhydrazide functionalities in their aglycone on to an aldehyde-functionalised polymer scaffold. PS-DCLs have been shown to undergo compositional change in response to the addition of lectin templates, with polymer scaffolds preferentially incorporating carbohydrate units which recognise the lectin added. This compositional change has been shown to generate polymers of significantly enhanced affinity for the lectin added, with enhancements in free energy of binding in the range of 5.2-8.8 kJ mol-1 observed. Experiments indicate that these enhancements are not only as a consequence of increased display of the preferred carbohydrate upon the polymer scaffold, but that templation also reorganises key residues into strategic positions in order to interact more strongly with the target. This journal is
- Mahon, Clare S.,Fascione, Martin A.,Sakonsinsiri, Chadamas,McAllister, Tom E.,Bruce Turnbull,Fulton, David A.
-
supporting information
p. 2756 - 2761
(2015/04/22)
-
- Orthogonal breaking and forming of dynamic covalent imine and disulfide bonds in aqueous solution
-
Orthogonal bond-breaking and forming of dynamic covalent disulfide and imine bonds in aqueous solution is demonstrated. Through judicious choice of reaction partners and conditions, it is possible to cleave and reform selectively these bonds in the presence of each other in the absence of unwanted competing processes.
- Bracchi, Michael E.,Fulton, David A.
-
supporting information
p. 11052 - 11055
(2015/07/02)
-
- 2-THIO-1,3,4-OXADIAZOLES DERIVATIVES AS SPHINGOSINE-1 PHOSPHATE RECEPTORS MODULATORS
-
The present invention relates to novel 2-thio-1,3,4-oxadiaZ oles derivatives, processes for preparing them, pharmaceutical compositions containing them and their use as pharmaceuticals as modulators of sphingosine1-l-phosphate receptors.
- -
-
Paragraph 0138-0139
(2014/05/20)
-
- Synthesis and properties of a meso- tris-ferrocene appended zinc(ii) porphyrin and a critical evaluation of its dye sensitised solar cell (DSSC) performance
-
A zinc(ii) porphyrin derivative, F3P, was prepared containing a single ferrocene group appended at three of the meso positions. The final meso position contains a benzoic acid unit, and was designed to be an anchoring moiety to a semiconductor surface. The cyclic voltammogram for the porphyrin derivative reveals that the three ferrocene units are oxidised and reduced at E 1/2 = +0.04 V vs. Fc+/Fc. Other redox responses are porphyrin-based at +1.1 V vs. Fc+/Fc (irreversible) and -1.87 V and -2.20 V vs. Fc+/Fc (both quasi-reversible). The room temperature Moessbauer spectrum for F3P comprises a doublet (δ Fe 0.44 mm s -1; ΔEQ 2.35 mm s-1; peak width 0.27 mm s-1). The data are consistent with the ferrocene groups non-interacting with the porphyrin moiety in the ground state. Excitation of the compound in THF with an ultra-short laser pulse produces in less than 1 ps the charge separated state which comprises Fc+-porp- and decays back to the ground state in 24 ps. Roughly the same behaviour is observed for the dye absorbed on TiO2, the only slight difference is the appearance of a long-lived component in the decay records. The electron for the porphyrin radical anion does not inject into the conduction band of the TiO 2, only the porphyrin excited state participates in any electron injection process. Partly because of this factor the performance of the dye attached to TiO2 in a DSSC device is rather limited (JSC = 0.068 mA cm-2, VOC = 283 mV, FF = 0.42, η = 0.008%). This journal is the Partner Organisations 2014.
- Sirbu,Turta,Benniston,Abou-Chahine,Lemmetyinen,Tkachenko,Wood,Gibson
-
p. 22733 - 22742
(2014/06/23)
-
- PREPARATION METHOD OF 4-AMINOMETHYLBENZOIC ACID
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The present invention relates to a preparation method of 4-aminomethylbenzoic acid comprising the following steps: preparing 4-carboxylbenzaldehyde or an alkyl ester thereof (methyl 4-formyl benzoate); reacting the 4-carboxylbenzaldehyde or an alkyl ester thereof (methyl 4-formyl benzoate) with hydroxyamine to oximate the same; and contact reducing 4-carboxylbenzaldehyde oxime or an alkyl ester oxime thereof obtained by the oximation, through hydrogen in a sodium hydroxide aqueous solution. Since methyl 4-hydroxyiminomethylbenzoate is reacted as a raw material in the presence of an alkali, hydrogen of a relatively low pressure can be used and a purification process is also simple, thereby enabling preparation of 4-aminomethylbenzoic acid with a low cost and high yield.
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Page/Page column 4
(2012/12/13)
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- Chelating carboxylic acid amides as robust relay protecting groups of carboxylic acids and their cleavage under mild conditions
-
Free choice: Carboxamides of bispicolylamine are alternative protecting groups for carboxylic acids (see scheme). As a consequence of their straightforward applicability, their high chemical stability towards a broad range of conditions, and their selective cleavage under mild conditions to give either carboxylic acids or their methyl esters, this new protection method should find widespread application in the realm of organic synthesis. Copyright
- Broehmer, Manuel C.,Mundinger, Stephan,Braese, Stefan,Bannwarth, Willi
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scheme or table
p. 6175 - 6177
(2011/08/03)
-
- PH triggered self-assembly of core cross-linked star polymers possessing thermoresponsive cores
-
Core cross-linked star polymers possessing responsiveness to pH and temperature stimuli have been prepared, and we demonstrate how changes to pH and temperature can be used to trigger the release and uptake of a hydrophobic dye.
- Jackson, Alexander W.,Fulton, David A.
-
supporting information; experimental part
p. 6807 - 6809
(2011/08/21)
-
- Templating a polymer-scaffolded dynamic combinatorial library
-
A water soluble polymer-scaffolded dynamic combinatorial library whose members can interconvert through acylhydrazone exchange was prepared and shown to re-equilibrate in the presence of macromolecular templates.
- Mahon, Clare S.,Jackson, Alexander W.,Murray, Benjamin S.,Fulton, David A.
-
supporting information; experimental part
p. 7209 - 7211
(2011/09/12)
-
- Carbon tetrabromide/sodium triphenylphosphine-m-sulfonate (TPPMS) as an efficient and easily recoverable catalyst for acetalization and tetrahydropyranylation reactions
-
A solid complex, conveniently prepared from carbon tetrabromide and sodium triphenylphos-phine-m-sulfonate (TPPMS), can be used as an easily recoverable catalyst for the selective acetalization of aldehydes and tetrahydropyranylation of alcohols. The catalyst can be recovered by simple pre-cipitation with ether and can be reused at least 7 times without loss of catalytic activity.
- Huo, Congde,Chan, Tak Hang
-
experimental part
p. 1933 - 1938
(2011/02/28)
-
- Synthesis of succinimidoalkylbenzaldehyde analogues: Potential bifunctional linkers for bioconjugation
-
A series of novel 4-substituted benzaldehydes containing a succinimide moiety were synthesized as potential bifunctional linkers for the purpose of binding therapeutic drugs to antibodies raised against cancer cells. These potential benzaldehyde linkers varied in the nature of the para functionality so as to provide a range of potential acid labilities. Synthesis of the linkers involved a Williamson ether formation to make the ether linker 1, a Sonagoshira palladium-catalyzed coupling to synthesize the skeleton of the alkyl linker 2, and formation of an amide bond directly from a methyl ester gave the 4-substituted amide linker 3. As an example of the type of acetal that can be produced using these linkers, uridine was used as an analogue of the cytotoxic compound 5-fluorouridine to give the cyclic acetals 19?21. CSIRO 2008.
- Crosby, Ian T.,Pietersz, Geoffrey A.,Ripper, Justin A.
-
p. 138 - 143
(2008/04/04)
-
- The use of electroosmotic flow as a pumping mechanism for semi-preparative scale continuous flow synthesis
-
By employing a series of reactions we demonstrate the use of electroosmotic flow as a continuous pumping mechanism suitable for semi-preparative scale synthesis, affording an array of small organic compounds, of analytical purity, with yields ranging from 0.57-1.71 g h-1. The Royal Society of Chemistry.
- Wiles, Charlotte,Watts, Paul,Haswell, Stephen J.
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p. 966 - 968
(2007/12/31)
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- Acid-catalysed synthesis and deprotection of dimethyl acetals in a miniaturised electroosmotic flow reactor
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Through incorporating a series of polymer-supported acid catalysts into a miniaturised EOF-based flow reactor, we demonstrate a clean and efficient technique for the protection of aldehydes as their respective dimethyl acetal. In addition, we also report the acid catalysed deacetalisation of 11 dimethyl acetals to their respective aldehyde. In all cases, the compounds described are obtained in high yield (>95%) and excellent purity (>99%) without the need for further product purification.
- Wiles, Charlotte,Watts, Paul,Haswell, Stephen J.
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p. 5209 - 5217
(2007/10/03)
-
- Ruthenium(III) chloride-catalyzed chemoselective synthesis of acetals from aldehydes
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A mild and chemoselective acetalization procedure for the protection of various aldehydes in the presence of ketones is described.
- De, Surya K.,Gibbs, Richard A.
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p. 8141 - 8144
(2007/10/03)
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- Asymmetric polymer synthesis by repetitive Sakurai-Hosomi allylation reaction of compounds possessing both formyl and allylsilane functions
-
Trialkylallylsilanes generally react with aldehydes in the presence of a Lewis acid to the corresponding homoallylic alcohols. Chiral Lewis acids promote the same reaction to yield the enantiomerically-enriched homoallylalcohols. We have prepared four compounds (7-10) that possess both formyl and allylsilane functions. Lewis acids initiated self-polyaddition reactions of these compounds by means of repetitive allylation. The use of chiral Lewis acids resulted in the formation of optically active polymers that possess exo-methylene and secondary OH functions in their main chain. The optical purity of these chiral polymers was estimated based on the results of model asymmetric reactions between benzaldehyde and β-substituted allylsilanes and by controlled degradation.
- Itsuno, Shinichi,Kumagai, Toshihiro
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p. 3185 - 3196
(2007/10/03)
-
- Asymmetric synthesis of chiral polymers by means of repetitive addition of allylsilane to aldehyde
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Monomers having both allyltrimethylsilyl and formyl groups were prepared. Chiral (acyloxy)borane initiated the repetitive polyaddition of the monomers to give optically active polymers having main chain configurational chirality. Optical purity of the chiral polymer was evaluated by the analysis of the degradation product.
- Itsuno, Shinichi,Kumagai, Toshihiro
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p. 941 - 944
(2007/10/03)
-
- Efficient acetalisation of aldehydes catalyzed by titanium tetrachloride in a basic medium
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The acetalisation of aliphatic and aromatic aldehydes is achieved in a basic medium by using catalytic amount of Ti(IV) chloride in MeOH in the presence of NH3 or Et3N. The present protocol shows many advantages over the well known base or acid catalysis: in fact, in contrast to base-promoted acetalisation, aldehydes with electron-rich carbonyl groups react easily, enolizable aldehydes do not undergo aldol condensation and, in contrast to acid-catalysis, migration of the double bond does not occur in the preparation of α,β-unsaturated acetals.
- Clerici, Angelo,Pastori, Nadia,Porta, Ombretta
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p. 15679 - 15690
(2007/10/03)
-
- One-pot preparation of aroylsilanes by reductive silylation of methyl benzoates
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A one-pot synthesis of aroylsilanes based on reductive silylation of methyl benzoates using Mg/I2/chlorosilane in nontoxic 1-methyl-2- pyrrolidinone (NMP) solvent, is described. The yields are moderate to good and the method has been used for the preparation of some new bifunctional aroylsilanes.
- Tongco, Emily C.,Wang, Qunjie,Prakash, G.K. Surya
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p. 2117 - 2123
(2007/10/03)
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- 146. Polymer- and dendrimer-bound Ti-TADDO lates in catalytic (and stoichiometric) enantioselective reactions: Are pentacoordinate cationic Ti complexes the catalytically active species?
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α,α,α′,α′-Tetraaryl-1,3-dioxolane-4,5- dimethanols (TADDOLs), containing styryl groups either at C(2) of the heterocyclic ring or in the α-position, were prepared in the usual way (18-22, 24, 25). These compounds were copolymerized with styrene and divinylbenzene in a suspension, yielding polymers (33-40, Scheme 3) as beads with a rather uniform particle-size distribution (150-450 μm), swellable in common organic solvents, HOCH2- and BrCH2-substituted TADDOLs were also prepared and used for attachement to Merrifield resin or to dendritic molecules (23, 26-32). The TADDOL moieties in these materials are accessible to form Ti (and Al) complexes (Scheme 4) which can be used as polymer- or dendrimer-bound reagents (stoichiometric) or Lewis acids (catalytic). The reactions studied with these new chiral auxiliaries are: enantioselective nucleophilic additions to aldehydes (of R2Zn and RTi(OCHMe2)3; Schemes, Table 1) and to ketones (of LiAlH4, Table 2); enantioselective ring opening of meso-anhydrides (Scheme 6); [4+2] and [3+2] cycloadditions of 3-crotonyl-1,3-oxazolidin-2-one to cyclopentadiene and to (Z)-N-benzylidenephenylamine N-oxide (→ 48, 9, Scheme 7, Tables 3, , and Fig. ). The enantioselectivities reached with most of the polymer-bound or dendritic TADDOL ligands were comparable or identical to those observed with the soluble analogs. The activity of the polymer-bound Lewis acids was only slightly reduced as compared with that encountered under homogeneous conditions. Multiple use of the beads (up to 10 times), without decreased performance, has been demonstrated (Figs. 3 and 4). The poorer selectivity in the Diets-Alder reaction (Scheme 7a), induced by the polymer-bound Cl2Ti-TADDOLate as compared to the soluble one, is taken as an opportunity to discuss the mechanism of this Lewis-acid catalysis, and to propose a cationic, trigonal-bi-pyramidal complex as the catalytically active species (Fig. 6) It is suggested that similar cations may be involved in other Ti-TADDOLate-mediated reactions as well.
- Seebach, Dieter,Marti, Roger E.,Hintermann, Tobias
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p. 1710 - 1740
(2007/10/03)
-
- Thiazolidinedione hypoglycemic agents
-
Hypoglycemic thiazolidine-2,4-dione derivatives of the formula STR1 wherein the dotted line represents a bond or no bond; A and B are each independently CH or N, with the proviso that when A or B is N, the other is CH; X is S, SO, SO2, CH2, CHOH or CO; n is 0 or 1; Y is CHR1 or NR2, with the proviso that when n is 1 and Y is NR2, X is SO2 or CO; Z is CHR3, CH2 CH2, CH=CH, STR2 OCH2, SCH2, SOCH2 or SO2 CH2 ; R, R1, R2 and R3 are each independently hydrogen or methyl; and X1 and X2 are each independently hydrogen, methyl, trifluoromethyl, phenyl, benzyl, hydroxy, methoxy, phenoxy, benzyloxy, bromo, chloro or fluoro; a pharmaceutically-acceptable cationic salt thereof; or a pharmaceutically-acceptable acid addition salt thereof when A or B is N.
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-
- Process for separating dimethyl isophthalate and dimethyl orthophthalate from their mixture with dimethyl terephthalate
-
The invention relates to a process for separating dimethyl isophthalate (DMI) and dimethyl orthophthalate (DMO) and other by-products from their mixture with dimethyl terephthalate (DMT), formed in the oxidation of p-xylene followed by esterification with methanol, by crystallization from the melt. Initially, the esterification product is here distilled once or several times. The DMT-rich fraction obtained is then subjected wholly or partially to one or several crystallizations from the melt, and the DMI-DMO fraction thus obtained is at least partially removed from the system. As an alternative, the DMT-rich fraction is first recrystallized from methanol, the methanol is then evaporated from the mother liquor and the remaining residue is subjected to one or several crystallizations from the melt. The DMI-DMO fraction thus obtained is again at least partially removed from the system.
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