Facile synthesis of dopa‐functional polycarbonates via thiol‐Ene‐coupling chemistry towards self‐healing gels

Since extraction of the naturally occurring mussel‐foot proteins is expensive and time‐consuming, routes towards synthetic analogues are continuously being explored. Often, these methods involve several protection and deprotection steps, making the synthesis of synthetic analogues time‐consuming and expensive as well. Herein, we show that UV‐initiated thiol‐ene coupling between a thiol‐functional dopamine derivative and an allyl‐functional aliphatic polycarbonate can be used as a fast and facile route to dopa‐functional materials. Different thiol‐to‐allyl ratios and irradiation protocols were used and it was found that nearly 50% of the allyl groups could be functionalized with dopa within short reaction times, without the need of protecting the catechol. It is also demonstrated herein that the dopa‐functional polymers can be used to form self‐healing gels through complexation with Fe³⁺ ions at increased pH. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2370–2378     

Rings whose singular ideals are nil

Abstract

It is well known that when a ring R satisfies ACC on right annihilators of elements, then the right singular ideal of R is nil, in this case, we say R is right nil-singular. Many classes of rings whose singular ideals are nil, but do not satisfy the ACC on right annihilators, are presented and the behavior of them is investigated with respect to various constructions, in particular skew polynomial rings and triangular matrix rings. The class of right nil-singular rings contains π-regular rings and is closed under direct sums. Examples are provided to explain and delimit our results.     

The Effects of Ring Strain on Cyclic Tetraaryl[5]cumulenes

Cyclic tetraaryl[5]cumulenes ( 1 a–f ) have been synthesized and studied as a function of increasing ring strain. The magnitude of ring strain is approximated by the extent of bending of the cumulenic core as assessed by a combination of X-ray crystallographic analysis and DFT calculations. Trends are observed in ¹³C NMR, UV-vis, and Raman spectra associated with ring strain, but the effects are small. In particular, the experimental HOMO-LUMO gap is not appreciably affected by bending of the [5]cumulene framework from ca. 174° (λ_max=504 nm) in 1 a to ca. 178° (λ_max=494 nm) in 1 f .     

Rings with 2-UJ property

Abstract

Rings in which the square of each unit is a sum of an idempotent and an element from the Jacobson radical are said to be 2-UJ. Properties of 2-UJ rings are discussed, and the 2-UJ property is applied to characterize some known notions of rings.     

Dehydrohalogenation of isomeric 2- and 3-bromomethyl substituted 2,3-dihydrooxazolo[3,2-a]pyridines

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A new tricrystalline triblock terpolymer by combining polyhomologation and ring‐opening polymerization. synthesis and thermal properties

New tricrystalline triblock terpolymers, polyethylene‐block‐poly(ε‐caprolactone)‐block‐poly(L‐lactide) (PE‐b‐PCL‐b‐PLLA), were synthesized by ROP of ε‐caprolactone (CL) and L‐lactide (LLA) from linear ω‐hydroxyl polyethylene (PE‐OH) macroinitiators. The linear PE‐OH macroinitiators were prepared by C1 polymerization of methylsulfoxonium methylide (polyhomologation). Tin(II) 2‐ethylhexanoate was used as the catalyst for the sequential ROP of CL and LLA in one‐pot polymerization at 85 °C in toluene (PE‐OH macroinitiators are soluble in toluene at 80 °C). ¹H NMR spectra confirmed the formation of PE‐b‐PCL‐b‐PLLA triblock terpolymers through the appearance of the characteristic proton peaks of each block. GPC traces showed the increase in the number average molecular weight from PE‐OH macroinitiator to PE‐b‐PCL, and PE‐b‐PCL‐b‐PLLA corroborating the successful synthesis. The existence of three crystalline blocks was proved by DSC and XRD spectroscopy. © 2019 The Authors. Journal of Polymer Science Part A: Polymer Chemistry published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2450–2456     

Phosphido‐diphosphine pincer aluminum complexes as catalysts for ring opening polymerization of cyclic esters

New aluminum alkyl complexes, supported by o‐phenylene‐derived phosphido diphosphine pro‐ligands [Ph‐PPP]‐H and [ⁱPr‐PPP]‐H ([Ph‐PPP]‐H = bis(2‐diphenylphosphinophenyl)phosphine; [ⁱPr‐PPP]‐H = bis(2‐diisopropylphosphinophenyl)phosphine) are reported. Compounds [Ph‐PPP]AlMe₂ ( 1 ), [ⁱPr‐PPP]AlMe₂ ( 2 ), and [Ph‐PPP]AlⁱBu₂ ( 3 ) have been synthesized by reaction of the pro‐ligand with the appropriate trialkyl aluminum precursor and have been characterized by ¹H, ¹³C and ³¹P NMR spectroscopy. The solution NMR data and theoretical calculations suggest for all complexes trigonal bipyramidal structures with C_2v symmetry in which the phosphido diphosphine ligand acts as a κ³ coordinated ligand. All complexes promote the ring‐opening polymerization of ε‐caprolactone, L‐ and rac‐lactide. Polyesters with controlled molecular parameters (M_n, end groups) and low polydispersities are obtained. Upon addition of isopropanol, efficient binary catalytic systems for the immortal ring‐opening polymerization of the cyclic esters are produced. Preliminary investigations show the ability of these complexes to promote copolymerization of l ‐lactide and ?‐caprolactone to achieve copolymers whose microstructures are depending on the structure of the catalyst. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 49–60     

The structure of 11,12-bis[spiro(cyclopropyl)]-1,4,4a,5,8,8a,9a,10a-octahydro-1,4∶5,8-dimethano-9,10-anthraquinone

In the solid state the 21 Diels-Alder adduct between spiro[4.2]hepta-1,3-diene and p-benzoquinone has a planar cyclohexadione ring with a center of symmetry. Both planar and boat conformations have been observed in similar systems, and the relative stability of the two conformers is of interest. The adduct in the gas phase should contain a mirror plane perpendicular to the cyclohexadione ring; however, a data set collected on a crystal in a capillary resulted in a structure where some bond lengths related by this mirror plane differed by more than 4 in the solid state. Molecular mechanics, MOPAC, and the Cambridge Structural Data Base were used to investigate the factors influencing the conformation of the cyclohexadione ring and the asymmetry across the noncrystallographic mirror plane. The energy differences between the planar and nonplanar ring system is small, and the conformation is determined by crystal packing. No reason for the bond length asymmetry could be found, and a recollection of data on a crystal exposed to the environment led to a structure with statistically equivalent bond lengths.