Synthesis and ring-opening copolymerization of cyclic aryl ester dimers

Two kinds of cyclic aryl ester dimers have been synthesized by reaction of phthaloyl dichloride with bisphenols via interfacial polycondensation. The cyclic dimers readily undergo anionic ring-opening polymerization or copolymerization in the melt by using sodium benzoate as the initiator, producing linear, high molecular weight polyesters. The contents of cyclic dimers in the homopolymers P1, P2, and copolymer P12 are 13.7%, 10.2%, 2.9%, respectively, which indicates that ring-opening copolymerization of cyclic dimers may impel the conversion of cyclic dimers and decrease the content of cyclic dimers in the resulting copolymer. Moreover, the isothermal chemorheology of the ring-opening copolymerization of cyclic dimers indicates that the reactivemoltenmixture has low shear viscosity and the viscosity increases slowly in the initial stage of ring-opening polymerization.     

pH-Sensitive brush polymer-drug conjugates by ring-opening metathesis copolymerization

Representing a new category of polymer-drug conjugates, brush polymer-drug conjugates were prepared by ring-opening metathesis copolymerization. Following judicious structural design, these conjugates exhibited well-shielded drug moieties, significant water solubility, well-defined nanostructures, and acid-triggered drug release.     

Cationic ring-opening polymerization of new 1,6-anhydro-β-lactose derivatives

Synthesis and cationic ring-opening polymerization of new 1,6-anhydro-β-lactose derivatives such as hexa-O-methylated (LSHME), tert-butyldimethylsilylated (LSHSE), and benzylated 1,6-anhydro-β-lactoses (LSHBE) were first investigated. The disaccharide monomers were prepared by methylation, tert-butyldimethylsilylation, and benzylation of 1,6-anhydro-β-lactose, respectively. It was found that LSHME was readily polymerized with such Lewis acid catalysts as PF₅ and SbCl₅ to give stereoregular 2,3-di-O-methyl-4-O-(2′,3′,4′,6′-tetra-O-methyl-β-D -galactopyranosyl)-(1→6)-β-D -glucopyranans which are comb-shaped polysaccharide derivatives. However, LSHSE and LSHBE had almost no polymerizability. It was revealed that the ring-opening polymerizability of the anhydrodisaccharide monomers was influenced by the steric hindrance of the hydroxyl-protective groups. Ring-opening copolymerization of LSHME with 1,6-anhydro-2,3,4-tri-O-benzyl-β-D -glucopyranose (LGTBE) in various ratios of monomer feeds was also examined to afford the corresponding copolymers. Structural analyses of the monomers and polymers were carried out by means of high resolution nuclear magnetic resonance spectroscopy.     

Synthesis and ring-opening polymerization of new 1,4-anhydro-glucopyranose derivatives

Three new 1,4-anhydro-glucopyranose derivatives having different hydroxyl protective groups such as 1,4-anhydro-2,3,6-tri-O-methyl-α-D -glucopyranose (AMGLU), 1,4-anhydro-6-O-benzyl-2,3-di-O-methyl-α-D -glucopyranose (A6BMG), and 1,4-anhydro-2,3-di-O-methyl-6-O-trityl-α-D -glucopyranose (A6TMG) were synthesized from methyl α-D -glucopyranoside in good yields. Their polymerizability was compared with that of 1,4-anhydro-2,3,6-tri-O-benzyl-α-D -glucopyranose (ABGLU) reported previously. The trimethylated monomer, AMGLU, was polymerized by a PF₅ catalyst to give 1,5-α-furanosidic polymer having number-average molecular weights (M̄_n) in the range of 2.8 × 10³ to 6.8 × 10³. The ¹³C-NMR spectrum was compared with that of methylated amylose and cellulose. Other anhydro monomers, A6BMG and A6TMG, gave the corresponding 1,5-α furanosidic polymers having M̄_n = 17.1 × 10³ and 1.8 × 10³, respectively. Thus, the substituents at the C2 and C6 positions were found to play an important role for the ring-opening polymerizability of the 1,4-anhydro-glucose monomers. In addition, debenzylation of the tribenzylated polymer gave free (1 → 5)-α-D -glucofuranan. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 841–850, 1998     

Synthesis of 6-amino-3,4-dihydroisoquinolinium derivatives by ring-opening reactions of acridizinium ions

The reaction of the 9-fluoroacridizinium (9-fluorobenzo[b]quinolizinium) or the 9-aminoacridizinium (9-aminobenzo[b]quinolizinium) ion with primary alkyl amines gives with high diastereoselectivity 6-amino-3,4-dihydroisoquinolinium derivatives as main products, which exhibit pronounced absorption and fluorescence properties. It is proposed that the reaction proceeds via a nucleophilic ring-opening followed by an aza Diels-Alder reaction.     

Synthesis of 2-iminothiazoline derivatives by sequential conjugate addition/annulation/ring-opening reactions

1,2-Diaza-1,3-butadienes reacted with rhodanine affording 2-(mercaptoacetyl)iminothiazoline derivatives through conjugate addition/annulation/ring-opening/oxidative dimerization. The hypothesized ring-closure and ring-opening mechanism was supported by X-ray crystal structure analysis of a compound obtained by reaction of the same reagents with a chiral 1,3-oxazolidine-2-thione derivative.     

Synthesis of degradable copolymers by ring-opening polymerization

Hydrolysable copolymers made from different cyclic monomers have been studied. The monomers involved are 1,5-dioxepan-2-one (DXO), L-dilactide, 1,3-dioxan-2-one (TMC), oxepan-2,7-dione (AA) and oxepan-2-one (ϵ-CL). The hydrolysis of the DXO/L-dilactide copolymer showed great differences in degradation rate depending on composition. A statistical copolymer made from TMC and ϵ-CL was amorphous with a glass transition temperature of −48°C. TMC and AA could form a blockcopolymer with n-BuLi as initiator in toluene, 0°C.     

The anionic ring-opening polymerization and copolymerization of cyclic carbonates

Cyclic carbonates are eligible to ring-opening polymerization using a wide variety of initiators such as carbanionic or alcoholate species as well as initiators known to be effective for the ring-opening polymerization of lactones and for the group transfer polymerization of vinyl monomers. Depending on the catalyst, high molecular weight polymers may be obtained in high yields (kinetically controlled regime) or a ring-chain equilibrium is observed upon end-biting, back-biting and transesterification reactions (thermodynamically controlled regime). The polymerizability of the cyclic carbonates is strongly dependent on their structure. Five-membered cycles generally cannot be polymerized, whereas six-membered cycles can be polymerized and copolymerized in an ideal manner. The polymerizability of higher cyclics, in particular when containing aromatic ring systems, is highly dependent on the substitution pattern of the aromatics. Since the active species in the polymerization of aliphatic cyclic carbonates was disclosed to be of alcoholate type, a copolymerization with ϵ-caprolactone is easily achieved, the reactivity of the cyclic carbonate, however, being by far larger than that of the lactone. On the other hand, the copolymerization with pivalolactone exerts a different behaviour, since the active species of the growing pivalolactone chain after a few steps assumes the character of a carboxylate anion which is unable to promote the ring-opening polymerization of cyclic carbonates. Since carbanionic species may be used as initiators for the ring-opening polymerization of cyclic carbonates, polystyryl, polybutadienyl, and polyisoprenyl anions may be used as initiators to achieve the corresponding block copolymers. To obtain block copolymers with poly(methyl methacrylate) blocks a group transfer polymerization of the respective acrylate has to be performed, followed by the polymerization of the cyclic carbonate. The latter, however, rather proceeds by a metal- free anionic process than by a group transfer process. The ring-opening polymerization and copolymerization of cyclic carbonates allows the preparation of a broad variety of new polymers with remarkable properties.     

Synthesis and properties of stereoregular fluoro-polymers via ring-opening metathesis polymerization of fluorinated norbornenes and norbornadienes. An overview and progress report

Since the first report of the ring-opening metathesis polymerization of fluorinated monomers in 1979 considerable advances in precision and control of such syntheses have been achieved through the introduction of well defined initiators. It is now possible to carry out well controlled living and stereoregular polymerizations. The products of such syntheses can display unusually high relaxed dielectric constants, an observation which is crucial to the assignment of their tacticities and probably significant with regard to possible applications of this type of material.     

Copolymerization of 1,6-anhydroglucose and 1,6-anhydromaltose derivatives

The copolymerization of 1,6-anhydro-2,3,4-tri-O-(p-methyl-benzyl)-β-D -glucopyrnose [TXGL, M₁] with 1,6-anhydro-2,3-di-O-benzyl-4-O-(2,3,4,6-tetra-O-benzyl-α-D -glucopyranosyl)-β-D -glucopyranose [HBMA, M₂] has been studied as a method of producing dextrans of controlled composition with a linear backbone and randomly distributed single glucose units as side chains. Copolymers of intrinsic viscosities ranging from 0.51 to 0.05 dl/g are produced. The copolymerization appears to follow classical copolymerization theory but is affected adversely by the low reactivity of the maltose derivative. Reactivity ratios have been calculated for runs catalyzed by 10 mole-% and 20 mole-% phosphorus pentafluoride (PF₅): r₁ = 1.91 ± 0.35, r₂ = 0.28 ± 0.25 and r₁ = 2.21 ± 0.15, r₂ = 0.21 ± 0.10, respectively.     

Manganese-catalyzed ring-opening carbonylation of cyclobutanol derivatives

Herein, we report a manganese-catalyzed ring-opening carbonylation of cyclobutanol derivatives through cyclic CC bond cleavage. The reaction happens via a radical-mediated pathway to selectively generate 1,5-ketoesters. A variety of substrates with substituents on the aromatic ring reacted with linear alcohols of different chain lengths. Obtained aliphatic esters are very attractive since they are usually difficult to access.     

Enzymatic ring-opening copolymerization of trimethylene carbonate and ethylene ethyl phosphate

A growing interest in biodegradable polymers and their biomedical and pharmaceutical applications has developed since the past decade. Ring-opening polymerization has been regarded as an efficient route for the synthesis of the biodegradable polymers, such as polyester, polycar- bonates and polyphosphates[1—6]. However, chemical methods for the ring-opening polymerization of biodegradable polymers need extremely pure monomers and anhydrous conditions as well as metallic catalysts, which must …     

Synthesis of polyester having sequentially ordered two orthogonal reactive groups by anionic alternating copolymerization of epoxide and bislactone

This article presents a route to a novel polyester having sequentially ordered two orthogonal reactive groups. The polyester was given by the imidazole‐initiated alternating copolymerization of allyl glycidyl ether (AGE) and a bislactone 1 . This copolymerization system is characterized by the following three reaction behaviors: (1) the selective participation of only one of the two lactone moieties of 1 to the copolymerization to give a linear polyester, and the consequent introduction of the second lactone into the side chain of the polyester, (2) the participation of the epoxy moiety in AGE to the copolymerization, and the consequent introduction of the carbon–carbon double bond into the side chain of the polyester, and (3) arrangement of the sequentially ordered two orthogonal reactive groups according to the alternating manner. The introduction of the two reactive groups to the side chain of the alternating copolymer allowed two routes of sequential chemoselective reactions: (A) The ring‐opening reaction of the lactone moiety with n‐propylamine and the following Pt‐catalyzed hydrosilylation of the carbon–carbon double bond with dimethylphenylsilane and (B) the sequential reactions of the reverse order. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009     

Anionic ring-opening polymerization of silacyclobutane derivatives

Anionic polymerizations of 1,1-dimethylsilacyclobutane, 1,1-diethylsilacyclobutane and 1-methyl-1-phenylsilacyclobutane were investigated. Addition of 5 mol % of butyllithium to a solution of 1,1-dimethylsilacyclobutane in THF-hexane (1 : 1) at −48°C provided poly(1,1-dimethylsilabutane) in 99% yield. M_n and M_w/M_n of the obtained polymer were 2400 and 1.10. This polymerization proceeded with a living nature. M_n increased in proportion as the yield of polymer increased. Addition of the second fresh feed of the monomer to the reaction mixture restarted polymerization of the second monomer at the same rate as in the initial stage. Addition of styrene to the living poly(1,1-dimethylsilabutane) provided a poly(1,1-dimethylsilabutane-b-styrene) block copolymer. It was also found that a polymerization of 1,1-diethylsilacyclobutane in THF-hexane at −48°C showed a living nature. In contrast, a polymerization of 1-methyl-1-phenylsilacyclobutane in THF at −78°C did not show a living nature. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3207–3216, 1997