A Novel Polymeric Carbohydrate. Synthesis of (1→6)-2,5-Anhydro-d-glucitol by Regio- and Stereoselective Anionic Cyclopolymerization of 1,2:5,6-Dianhydro-d-mannitol
Abstract:The anionic cyclopolymerizations of 1,2:5,6-dianhydro-3,4-di-O-methyl-D-mannitol (1) and 1,2:5,6-dianhydro-3,4-O-isopropylidene-D-mannitol (2) have been carried out using potassium tert-butoxide (t-BuOK) and potassium hydroxide (KOH). For the polymerization of 1, a well-defined carbohydrate polymer consisting of (1f6) linked 2,5-anhydro-3,4-di-O-methyl-D-glucitol units was synthesized through a regio-and stereoselective mechanism. When a [1]/[t-BuOK] molar ratio of 20 was used in toluene for 48 h, the yields a… Show more
“…Molybdenum imido alkylidene N-heterocyclic carbene complexes (XXX−XXXII) show high functional group tolerance in the cyclopolymerization of 1,6-hepta-and 1,7octadiynes. 278,279 For example, the complex XXXa promotes the cyclopolymerization of the monomers having unprotected hydroxy groups (114) or carboxy groups (116 and 118). No high-quality 13 C NMR spectrum of those polymers with hydroxy or carboxy groups is available, probably because of the severe aggregation of those functional groups.…”
Section: Cyclopolymerization Of Diynes Eneynes and Bis(cycloolefin)smentioning
confidence: 99%
“…Cationic and anionic polymerization of 1,2:5,6-dianhydro-3,4-di- O -alkyl- d -mannnitols ( 35 ) − , and l -iditols ( 36 ) , and the mechanism for cationic polymerization of (i) 1,2:5,6-dianhydro-3,4-di- O -alkyl- d -mannnitols and (ii) l -iditols and anionic polymerization of (iii) 1,2:5,6-dianhydro-3,4-di- O -alkyl- d -mannnitols and (iv) l -iditols.…”
Section: Ionic Cyclopolymerizationmentioning
confidence: 99%
“…The anionic polymerization of 1,2:5,6-dianhydro-3,4-di- O -alkyl- d -mannnitols ( 35 ) and l -iditols ( 36 ) by t -BuOK also affords the polymer containing 1→6-linked 2,5-anhydro- d -glucitol units, but the regio- and stereospecificity is much higher (Figure ). − The anionic polymerization proceeds through successive β- and α-scission of the epoxides in the monomer (Figure (iii), (iv)). The molecular weight of the polymer can be controlled by the monomer-to-initiator molar ratio and the polymerization time, and end-functionalization is also possible .…”
Monomers possessing two functionalities suitable for polymerization are often designed and utilized in syntheses directed to the formation of cross-linked macromolecules. In this review, we give an account of recent developments related to the use of such monomers in cyclopolymerization processes, in order to form linear, soluble macromolecules. These processes can be activated by means of radical, ionic, or transition-metal mediated chain-growth polymerization mechanisms, to achieve cyclic moieties of variable ring size which are embedded within the polymer backbone, driving and tuning peculiar physical properties of the resulting macromolecules. The two functionalities are covalently linked by a "tether", which can be appropriately designed in order to "imprint" elements of chemical information into the polymer backbone during the synthesis and, in some cases, be removed by postpolymerization reactions. The two functionalities can possess identical or even very different reactivities toward the polymerization mechanism involved; in the latter case, consequences and outcomes related to the sequence-controlled, precision synthesis of macromolecules have been demonstrated. Recent advances in new initiating systems and polymerization catalysts enabled the precision syntheses of polymers with regulated cyclic structures by highly regio- and/or stereoselective cyclopolymerization. Cyclopolymerizations involving double cyclization, ring-opening, or isomerization have been also developed, generating unique repeating structures, which can hardly be obtained by conventional polymerization methods.
“…Molybdenum imido alkylidene N-heterocyclic carbene complexes (XXX−XXXII) show high functional group tolerance in the cyclopolymerization of 1,6-hepta-and 1,7octadiynes. 278,279 For example, the complex XXXa promotes the cyclopolymerization of the monomers having unprotected hydroxy groups (114) or carboxy groups (116 and 118). No high-quality 13 C NMR spectrum of those polymers with hydroxy or carboxy groups is available, probably because of the severe aggregation of those functional groups.…”
Section: Cyclopolymerization Of Diynes Eneynes and Bis(cycloolefin)smentioning
confidence: 99%
“…Cationic and anionic polymerization of 1,2:5,6-dianhydro-3,4-di- O -alkyl- d -mannnitols ( 35 ) − , and l -iditols ( 36 ) , and the mechanism for cationic polymerization of (i) 1,2:5,6-dianhydro-3,4-di- O -alkyl- d -mannnitols and (ii) l -iditols and anionic polymerization of (iii) 1,2:5,6-dianhydro-3,4-di- O -alkyl- d -mannnitols and (iv) l -iditols.…”
Section: Ionic Cyclopolymerizationmentioning
confidence: 99%
“…The anionic polymerization of 1,2:5,6-dianhydro-3,4-di- O -alkyl- d -mannnitols ( 35 ) and l -iditols ( 36 ) by t -BuOK also affords the polymer containing 1→6-linked 2,5-anhydro- d -glucitol units, but the regio- and stereospecificity is much higher (Figure ). − The anionic polymerization proceeds through successive β- and α-scission of the epoxides in the monomer (Figure (iii), (iv)). The molecular weight of the polymer can be controlled by the monomer-to-initiator molar ratio and the polymerization time, and end-functionalization is also possible .…”
Monomers possessing two functionalities suitable for polymerization are often designed and utilized in syntheses directed to the formation of cross-linked macromolecules. In this review, we give an account of recent developments related to the use of such monomers in cyclopolymerization processes, in order to form linear, soluble macromolecules. These processes can be activated by means of radical, ionic, or transition-metal mediated chain-growth polymerization mechanisms, to achieve cyclic moieties of variable ring size which are embedded within the polymer backbone, driving and tuning peculiar physical properties of the resulting macromolecules. The two functionalities are covalently linked by a "tether", which can be appropriately designed in order to "imprint" elements of chemical information into the polymer backbone during the synthesis and, in some cases, be removed by postpolymerization reactions. The two functionalities can possess identical or even very different reactivities toward the polymerization mechanism involved; in the latter case, consequences and outcomes related to the sequence-controlled, precision synthesis of macromolecules have been demonstrated. Recent advances in new initiating systems and polymerization catalysts enabled the precision syntheses of polymers with regulated cyclic structures by highly regio- and/or stereoselective cyclopolymerization. Cyclopolymerizations involving double cyclization, ring-opening, or isomerization have been also developed, generating unique repeating structures, which can hardly be obtained by conventional polymerization methods.
“…Shultz et al first proposed a novel class of hosts, macromolecular ionophores, which have a mimetic structure of naturally occurring ionophores involving polyether antibiotics, such as monensin and nigericine 22. In addition, we reported that a carbohydrate polymer consisting of (1→6)‐linked 2,5‐anhydrohexitol, which was synthesized via the regio‐ and stereoselective cyclopolymerization of 1,2:5,6‐dianhydrohexitol, acted as a macromolecular ionophore possessing a size‐selective cation‐binding ability for metal cations and a chiral discrimination ability for racemic amino acids 23–28. These molecular recognitions were assumed to be based on the fact that the helical conformers of these polymers varied their pitch and cavity size for optimizing the multidentate coordination with a given cation.…”
“…We have reported the regio- and stereoselective cyclopolymerization of 1,2:5,6-dianhydrohexitols as a new method for producing a carbohydrate polymer. − Using each of the cationic and anionic initiators, 1,2:5,6-dianhydrohexitols produced polymers consisting of cyclic constitutional repeating units without cross-linking reactions. The polymer obtained by cationic polymerization was composed mainly of a five-membered cyclic unit along with the other cyclic ones. − On the other hand, polymerization using the anionic initiator proceeded through a highly regio- and stereoselective mechanism to yield a polymer consisting only of the 2,5-anhydrohexitol unit. − For instance, 1,2:5,6-dianhydro-3,4-di- O -methyl- d -mannitol ( 1 ) was polymerized with potassium tert -butoxide ( t -BuOK) to yield (1→6)-2,5-anhydro-3,4-di- O -methyl- d -glucitol ( 2 ). , 1 …”
The effect of 18-crown-6 ether (18C6) in the anionic cyclopolymerization of 1,2:5,6-dianhydro-3,4-di-O-methyl-D-mannitol (1) using potassium tert-butoxide (t-BuOK) was studied. The addition of 18C6 did not affect the regio-and stereoselectivity in the polymerization of 1, and the resultant polymer was (1f6)-2,5-anhydro-3,4-di-O-methyl-D-glucitol (2). The complexation of t-BuOK with 18C6 increased the initiator efficiency from 0.3 to 1.0, which was accompanied by enhancement of the apparent polymerization rate. The rate constant ratios of the transfer reaction to the propagation (ktr/kp) in the systems with and without 18C6 were 1 order of magnitude lower than the value in the polymerization of monoepoxides.The "living" nature of the t-BuOK/18C6 initiating system was evaluated by the two-step monomer resumption experiment.
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