Synthesis and ring‐opening polymerization of 1,4:2,5:3,6‐trianhydro‐D‐mannitol and structure studies by MNDO calculations

Abstract

Base-catalyzed intramolecular nucleophilic substitution of various dianhydrosorbitol derivatives (2,4, or 6) led to formation of trianhydromannitol(7), a tricyclic system of three interlinked oxolane rings. By treatment with trifluoromethanesulfonic acid, ring-opening reactions were achievedto give oligomeric soluble material with a number-average degree of polymerization DP, = 5 -10. Molecular weights were determined by GPC, and by desorptive chemical ionization (DCI) with ammonia a molecular weight assignment gave information on the degree of crosslinking. A complex but consistent picture allows to explain the propagation reactions of protonated trianhydromannitols 8 and 9, and further reactions of the protonated intermediates 13-15 to result in crosslinked products 16 and 17. By semiempirical quantum chemical calculations, geometries, energies and charge distributions of 7 as well as its protonated species were obtained. This allowed comparisons with their chemical reactivity and ring-opening specificity.Syntheses of monomeric compounds were followed by TLC on silica gel foils GF,,, (Merck). Detection was done by UV and/or spraying with 10% ethanolic sulfuric acid with subsequent heating to about 300°C. For column chromatography silica gel 60 (70-230 mesh, Merck) was used, and 'H NMR (300 MHz) and I3C NMR (75,46 MHz) were elaborated on a Bruker spectrometer WM 300.The number-average molecular weight D,, was determined using a Knauer vapor pressure osmometer. Selective polymer fraction_s of poly(oxy-2,3-diethoxytetramethylene) were isolated and cleaned by GPC and their exact M,, measured by vapor pressure osmometry. These values served as a basis for the calibration curve which was used to establish the weight-average molecular weight a, by GPC. GPC was performed using the combined instruments: pump (Knauer, analytical), differential refractometer type 98,00 (Knauer), integrator (Spectra-Physics). The molecular weights were determined by use of the Winner system and the GPC software (Spectra-Physics) on a XT-PC (Epson).For mass spectra and GC/MS measurements the equipment CH-7A (Varian), MAT and MAT 8230 (Finnigan-MAT GC/MS coupling, 70 eV) were applied and desorptive chemical ionization (DCI) spectra were obtained with MAT 8230 (Finnigan-MAT) using ammonia as reactant gas. Syntheses

Architectural Control of Isosorbide-Based Polyethers via Ring-Opening Polymerization

“…ROP of 5 can be conducted at low temperature with Sc­(OTf) 3 /PO to achieve higher conversion (14%, 0 °C; Table S8). , The conversions obtained across all systems are consistent with previous reports of 5 having a low ceiling temperature (4–16%, 4 °C). , Unreacted 5 can also be recovered in a pure state by sublimation of the crude polymerization mixture, allowing for straightforward recovery of the monomer (see SI). This operation could be implemented as a recycle stream in an industrial process.…”

“…For example, our group has shown isosorbide-based (meth)­acrylates have glass transition temperatures near that of poly­(styrene) and are good sustainable candidates for the glassy component in thermoplastic elastomers. − However, radical polymerization typically employs isosorbide as a pendant group from a vinyl or (meth)­acrylic backbone, − rendering the polymer backbone nondegradable. Alternatively, ring-opening polymerization (ROP) has been employed as a strategy to incorporate heteroatoms into the polymer backbone, only to produce short oligomers and cross-linked material . In attempts to synthesize copolymers, <10 mol % of isosorbide was incorporated into materials primarily composed of poly­(tetrahydrofuran) .…”

“…There are several examples of well-defined polyethers synthesized by ROP (i.e., ethylene oxide, oxetane, and tetrahydrofuran), but other polyethers are hard to obtain as the monomers do not have sufficient ring strain . Despite its perceived ring strain, attempts to polymerize trianhydrohexitol 5 have been largely unsuccessful. , To first investigate if sufficient ring strain was present in 5 , we employed DFT calculations using an isodesmic reaction (Scheme S1; see Supporting Information [SI] for computational details). The two distinct ethers present in 5 have significantly different ring-strain enthalpies (Δ H ): Δ H = −15.2 kcal mol –1 for the bridgehead ether and −9.1 kcal mol –1 for the terminal ethers .…”

“…However, cationic ROP (cROP) was the only method that resulted in successful homopolymerization ( M n up to 10 600 g mol –1 , DP ∼ 80). Previously, only short oligomers (DP ∼ 5) have been achieved . Studies to investigate the cROP mechanism of 5 in detail were then performed.…”

Regio- and Stereoselective Cyclopolymerization of 1,2:5,6-Dianhydroallitol and 1,2:5,6-Dianhydrogalactitol Leading to a Novel Carbohydrate Polymer of (2→6)-1,5-Anhydro-dl-galactitol

“…Monosaccharides, such as d -glucose and d -mannitol, are used as raw materials for monomers in ring-opening polymerization, addition polymerization, and polycondensation. − Recently, we have developed the cyclopolymerization of 1,2:5,6-dianhydrohexitol as a novel method for producing carbohydrate polymers with regio- and stereoselective structures; e.g., (1→6)-2,5-anhydro- d -glucitol was synthesized from the anionic cyclopolymerizations of 1,2:5,6-dianhydro- d -mannitol and 1,2:5,6-dianhydro- l -iditol and (1→6)-2,5-anhydro- d -mannitol- co -2,5-anhydro- l -iditol from 1,2:5,6-dianhydro- d -glucitol. − These polymers consisted essentially of five-membered cyclic repeating units. The possibility of forming the six-membered unit is of interest in connection with a new development in the synthesis of carbohydrate polymers by cyclopolymerization.…”