With the aid of a chiral template molecule functional groups could be placed in a highly crosslinked polymer in such a way that they are present in a chiral cavity in a given stereochemistry. By this method methyl, resp. 4-nitrophenyl α-D-mannopyranoside-2,3; 4,6-di-O-(4-vinylphenylboronate) (1a, resp. 1b) were copolymerized to macroporous polymers from which the templates methyl, resp. 4-nitrophenyl α-D-mannopyranoside (2a, resp. 2b) could be split off in return. It could be shown that such polymers with two boronic acid groupings within the chiral cavity possess a good ability for the resolution of racemates of the template used. In the case of the separation of the enantiomers of 2b separation factors up to 2,27 could be obtained. The overall optical enrichment in a chromatographic separation amounted to 87%.

Enzyme‐analogue built polymers, 4. On the synthesis of polymers containing chiral cavities and their use for the resolution of racemates

This perspective summarizes the chemistry of boroxines and outlines progress towards incorporating these ring structures into functional materials and macromolecular architectures. Special attention is paid to the dynamic covalent chemistry of boroxine ring construction and how these processes lead to novel molecular architectures and functional materials. Also highlighted in this perspective is the rich chemistry surrounding boroxine–ligand interactions and how these interactions flavor many areas of boroxine chemistry.

Boroxine chemistry and applications: A perspective

At its basic conceptualization, photoclick chemistry embodies a collection of click reactions that are performed via the application of light. The emergence of this concept has had diverse impact over a broad range of chemical and biological research due to the spatiotemporal control, high selectivity, and excellent product yields afforded by the combination of light and click chemistry. While the reactions designated as "photoclick" have many important features in common, each has its own particular combination of advantages and shortcomings. A more extensive realization of the potential of this chemistry requires a broader understanding of the physical and chemical characteristics of the specific reactions. This review discusses the features of the most frequently employed photoclick reactions reported in the literature: photomediated azide-alkyne cycloadditions, other 1,3-dipolarcycloadditions, Diels-Alder and inverse electron demand Diels-Alder additions, radical alternating addition chain transfer additions, and nucleophilic additions. Applications of these reactions in a variety of chemical syntheses, materials chemistry, and biological contexts are surveyed, with particular attention paid to the respective strengths and limitations of each reaction and how that reaction benefits from its combination with light. Finally, challenges to broader employment of these reactions are discussed, along with strategies and opportunities to mitigate such obstacles.

Photoclick Chemistry: A Bright Idea.

Phosphines are an important class of ligands in the field of metal-catalysis. This has spurred the development of new routes toward functionalized phosphines. Some of the most important C–P bond formation strategies were reviewed and organized according to the hybridization of carbon in the newly formed C–P bond.

https://www.beilstein-journals.org/bjoc/content/pdf/1860-5397-10-106.pdf

Preparation of phosphines through C-P bond formation.

This paper is a literature survey of quaternary ammonium, sulfonium, and phosphonium polymers.

Cationic Quaternary Polyelectrolytes—A Literature Review

Phosphorus-Containing Monomers. I. The Synthesis of Vinyl Phosphines, Oxides, Sulfides, and Phosphonium Compounds

As a step toward the better understanding of acrylonitrile polymerization a kinetic study was made in bulk with azo and peroxy catalysts over the range 30 to 60°C. Rates were followed gravimetrically in most cases, and molecular weights were estimated from viscosity measurements. Electron micrographs and nitrogen sorption data were obtained. Following a short induction period (which could not be eliminated) polymer separated as a fine suspension, coagulated to form curds at a few tenths percent polymerization and formed a hard, porous mass at about 60% reaction. Product at 5 to 50% polymerization was in the form of dense particles about 0.5 micron across; these appeared to be aggregates of 400 A. particles. The rate of polymerization accelerated up to 1–3% conversion and was then nearly constant to about 50%, beyond which it could not be measured. Rate increased with the 0.8 power of catalyst concentration and showed an over-all activation energy of 35 to 37 kcal./mole. Molecular weight varied inversely with the 0.2 power of the catalyst concentration, was nearly constant from 5 to 50% conversion and went through a slight maximum with temperature. To account for these observations a kinetic scheme is proposed that involves the possibility of unimolecular chain termination by a process of “burial.” This process is conceived of as a mechanism by which a growing chain may become shielded from further growth by coiling or embedding itself in the solid phase. Equations derived for rate and degree of polymerization fit the data adequately. Consideration is given to the simultaneous effects at high conversion of a small loss in initiator by thermal decomposition, of enrichment of the solution by shrinking liquid volume and of depletion of monomer.

Kinetics of acrylonitrile polymerization in bulk

Previous kinetic studies of acrylonitrile polymerization in bulk disclosed unexpected features that were associated with the heterogeneous nature of the system. In the present work, polymerization was carried out in homogeneous solution, principally in dimethyl formamide. Polymerization rate in dimethylformamide was dependent on the square root of the azo initiator concentration and approximately on the three-halves power of the monomer concentration. Over-all activation energy was 21 kcal./mole. Rates were slow in this solvent and molecular weights were low. Chain transfer activity of several liquids was estimated by substituting them for part of the dimethylformamide. Contrast between results in the homogeneous and heterogeneous cases is explained as due to removal by solvent of any opportunity for radical burial or catalyst enrichment. Standard kinetic treatments do not explain quite adequately the details of rate and molecular weight dependence on monomer. It appears that sluggish radicals are formed by chain transfer to solvent. A kinetic scheme is proposed to account for these observations.

Acrylonitrile polymerization in homogeneous solution

p-Vinylphenylboronic acid was prepared by the reaction of p-vinylphenyl magnesium chloride with tributyl borate. It is similar to styrene in respect to rate of free radical polymerization. Loss of boron is not significant during polymerization or handling. The polymer is a polyelectrolyte, soluble only in liquids containing some water. Films are clear, colorless, and brittle. On heating the polymer first becomes crosslinked by dehydration, then undergoes severe weight loss at 380 to 400°. Copolymerization behavior is that of an active monomer with an electron-deficient vinyl group.

Polymerization of vinyl monomers containing boron II. p‐vinylphenylboronic acid

Diphenyl-p-styrylphosphine (I), prepared by the reaction of diphenylchlorophosphine with p-styrylmagnesium chloride, was converted to the corresponding oxide (II) and sulfide (III) by treatment with tert-butyl hydroperoxide and sulfur, respectively. These substituted styrenes polymerize readily with thermal or free radical initiation to high molecular weight polymers. These polymers are somewhat more thermally stable than polystyrene. Thus their Ti's in air were in the range 320–365°C. and in nitrogen, 375–395°C. Their T10's were in the 390–415°C. range in air and 425–435°C. in nitrogen. Polystyrene in air has a Ti of 263°C. and a T10 of 340°C. The monomers copolymerize readily with styrene and methyl methacrylate, the low conversion polymers always containing more phosphorus than the monomer mixtures. Reactivity ratios were determined, from which Q and e values were calculated. These values for the following monomer pairs are (phosphorus monomer M2): styrene-I, r1 0.52, r2 1.43, Q2 1.34, e2 −0.30; styrene-II, r1 0.42, r2 1.40, Q2 1.34, e2 −0.07; styrene-III, r1 0.43, r2 1.49, Q2 1.37, e2 −0.13; MMA-I, r1 0.32, r2 0.91, Q2 1.58, e2 0.80; MMA-II, r1 0.38, r2 1.46, Q2 1.42, e2 −0.35; MMA-III, r1 0.29, r2 1.22, Q2 1.58, e2 −0.62. Analysis of these data indicates that these phosphorus moieties are activating through strong electronegative effects. The extent of activation is intermediate in intensity between mildly activating groups (e.g. Cl) and strongly activating groups (e.g. CN or NO2). The behavior of diphenyl-p-styrylphosphine is of particular interest in this respect, since its electronegativity points to strong electron delocalization.

Synthesis, polymerization, and copolymerization of diphenyl‐p‐styrylphosphine, phosphine oxide, and phosphine sulfide

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