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Amphiphilic boronic acid (BA)‐substituted block copolymers have been utilized in biomedical applications through binding to saccharides, including to glucose whereas binding to the anaerobically produced metabolite lactate is unreported. Glucose requires basic conditions, while lactate binding occurs at neutral physiological conditions. Herein, BA binding to glucose and lactate is used for the first time to convert solvated hydrophobic homopolymer and hydrophobic block copolymers to amphiphilic core‐shell nanoparticle spheres and worms.

The reactivity of hydrogen peroxide and catalytic hydroiodic acid toward 3,6-dimethoxy-2-(cycloamino)anilines is tunable to give ring-fused benzimidazoles or 1,4,6,9-tetramethoxyphenazine in high yield. Mechanisms via a detected nitroso-intermediate are proposed for oxidative cyclization and the unexpected intermolecular displacement of the oxazine. An aqueous solution of molecular iodine is capable of the same transformations. Oxidative demethylation gave targeted benzimidazolequinones, including without cleavage of the incorporated oxetane.

3,6-Dimethoxy-2-(cycloamino)anilines undergo 4- or 6-electron oxidations to afford novel ring-fused halogenated benzimidazoles or benzimidazolequinones using H2O2/HCl or H2O2/HBr. Cl2and Br2are capable of the same oxidative transformation to the benzimidazolequinones. Labeling experiments indicate that water is necessary for oxidation of the para-dimethoxybenzenes to the corresponding quinones.

The main modes of heterocyclic-ring synthesis in 2012 were cycloaddition, multi-component reactions, metathesis and oxidative dehydrogenation and amination reactions with copper, iron, palladium and rhodium being the most widely used transition metal catalysts. There is however a significant number of heterocycles now efficiently prepared in the absence of catalysts. Particularly noteworthy is the utilization of iodine reagents and radical oxidants as effective alternatives.

A new synthetic route to ring‐fused imidazo[5,4‐f]benzimidazoles is reported that can be used to access symmetrical and unsymmetrical quinone anticancer agents. Oxone in formic acid allows cyclisation of o‐tert‐aminoacetanilides to give ring‐fused benzimidazoles and imidazobenzimidazoles in superior yields. A mechanism for these oxidative cyclisations is proposed that proceeds through a hydrogen‐bonded amine N‐oxide intermediate. The amine N‐oxide is shown to act as an oxidant in the aromatisation to the imidazole ring. X‐ray crystal structures of the dimorpholine N‐oxide intermediate and bis[1,4]oxazinoimidazo[5,4‐f]benzimidazolequinone bis(trifluoroacetate) adduct are included. Two unsymmetrical quinones are shown to have greater cytotoxicity than the previously reported imidazobenzimidazolequinones.

The nitroxidemediated polymerization of Ntertbutylacrylamide TBAM in DMF at 120 °C using SG1DEPN and AIBN has been investigated. Linear growth in numberaverage molecular weight $\overline M _{\rm n}$ versus conversion and narrow molecular weight distributions MWDs with high livingness were obtained up to 8 000 g · mol−1. For higher molecular weights, the MWDs gradually became broader with low molecular weight tailing, and $\overline M _{\rm n}$deviated downwards from theoretical values. Quantitative analyses of MWDs, along with specifically designed conventional radical polymerizations at 120 °C, were consistent with chain transfer to monomer limiting the attainable $\overline M _{\rm n}$. This finding can be equally applied to existing literature polymerizations of TBAM.

Nitroxide-mediated controlled/living radical precipitation polymerization of styrene in supercritical carbon dioxide has been performed using SG1 and AIBN as mediator and initiator, respectively. The equivalent bulk polymerization proceeded at a rate ≈1.58 times faster than the precipitation polymerization. The number of chains increased with conversion to a similar extent in precipitation and bulk systems. A chain transfer mechanism to the Diels‐Alder dimer is used to explain the increase in numbers of chains. High conversions were also achieved for a conventional precipitation polymerization of styrene in scCO2 at 110 °C. The polymer was obtained as a powder, which contained cavities when observed under an SEM.

The key step in the synthesis of new five, six and seven‐membered alicyclic ring [1,2‐a]‐fused bioreductive benzimidazolequinones was radical cyclisation. Six and seven‐membered tributyltin hydride‐mediated homolytic aromatic substitutions of nucleophilic N‐alkyl radicals onto the benzimidazole‐2‐position occurred in high yields (63–70 %) when quaternising the pyridine‐like 3‐Nof imidazole with camphorsulfonic acid and using large excesses of the azo‐initiator, 1,1′‐azobis(cyclohexanecarbonitrile), to supplement the non‐chain reaction. Elaboration of benzimidazoles to the benzimidazolequinones occurred in excellent yields. The IC50values for the cytotoxicity of benzimidazolequinones towards the human skin fibroblast cell line GM00637 were in the nanomolar range, as determined by using the MTT assay. The benzimidazolequinones were much more cytotoxic than indolequinone analogues. 1,2,3,4‐Tetrahydropyrido[1,2‐a]benzimidazole‐6,9‐dione was the most potent compound prepared being more than 300 times more cytotoxic than the clinically used bioreductive drug, mitomycin C. The latter benzimidazolequinone was more potent under hypoxic conditions (associated with solid tumors), being 4.4 times more cytotoxic than under aerobic conditions, while mitomycin C was 1.8 times more selective towards hypoxia. The cyclopropane fused pyrido[1,2‐a]benzimidazolequinone, 1a,2,3,9b‐tetrahydro‐1H‐cyclopropa[3,4]pyrido[1,2‐a]benzimidazole‐5,8‐dione was less cytotoxic and selective than the five‐membered ring analogue, 1,1a,8,8a‐tetrahydrocyclopropa[3,4]pyrrolo[1,2‐a]benzimidazole‐3,6‐dione. Modifying the structure of the most potent pyrido[1,2‐a]benzimidazolequinone by attaching methyl substituents onto the quinone moiety increased reductive potentials and decreased cytotoxicity and selectivity towards hypoxia.

The copolymerization of N‐isopropylacrylamide (NIPAM) and N‐tert‐butylacrylamide (TBAM) via conventional radical polymerization and nitroxide‐mediated polymerization (NMP) with N‐tert‐butyl‐N‐[1‐diethylphosphono‐(2,2‐dimethylpropyl)]nitroxide (SG1) was investigated. The monomer reactivity ratios were determined to be 0.58 and 1.00 for NIPAM and TBAM, respectively. The reactivities were approximately the same at 120 and 60 °C in N,N‐dimethylformamide (DMF) and toluene, respectively, for the conventional copolymerizations and in DMF at 120 °C for NMP. Controlled/living characteristics for NMP were achieved with a 2,2′‐azobisisobutyronitrile/SG1 bimolecular system and a unimolecular polystyrene [poly(STY)]–SG1 macroinitiator in the presence of excess free SG1. Block copolymers of poly(N‐isopropylacrylamide‐stat‐N‐tert‐butylacrylamide) [poly(NIPAM‐stat‐TBAM)] with styrene {poly(N‐isopropylacrylamide‐stat‐N‐tert‐butylacrylamide)‐block‐polystyrene [poly(NIPAM‐stat‐TBAM)‐block‐poly(STY)]} were obtained by chain extension of either poly(NIPAM‐stat‐TBAM)–SG1 with styrene or poly(STY)–SG1 with NIPAM/TBAM. A comparison of the number‐average molecular weight calculated from the end‐group content with the number‐average molecular weight measured by gel permeation chromatography for poly(NIPAM‐stat‐TBAM)‐block‐poly(STY)–SG1 indicated that nearly all poly(NIPAM‐stat‐TBAM) chains were capped by SG1 and were thus living. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6410–6418, 2006

Nitroxide-mediated controlled/living dispersion polymerization of styrene in supercritical carbon dioxide (scCO2) has been performed successfully to high conversion using N-tert-N-butyl-N-1-diethylphosphono-(2,2-dimethylpropyl) nitroxide (SG1) and a poly(dimethylsiloxane-b-methyl methacrylate) stabilizer at 110 °C. The molecular weight distributions were narrow (Mw/Mn 1.12−1.43), and the number-average molecular weight (Mn) values agreed well with theory. A large excess of free SG1 was required to obtain satisfactory control in the dispersion polymerization, possibly due to SG1 partitioning. The critical degree of polymerization at which the polymer precipitates (Jcrit) was determined as 28 by visual observation using a novel approach. Polymerizations conducted in solution (toluene) proceeded at a similar rate (∼20% faster) to those in scCO2. The number of chains increased with conversion in both dispersion and solution, with the greater increase being observed in the dispersion system.

Summary:Nitroxide‐mediated dispersion polymerization of styrene in supercritical carbon dioxide has been performed successfully at 110 °C using a new polymeric so‐called inistab species, which fulfils the dual functions of an initiator and a colloidal stabilizer. The inistab species comprised a poly(dimethylsiloxane) block and a polystyrene block end‐capped with the nitroxide N‐tert‐N‐butyl‐N‐[1‐diethylphosphono‐(2,2‐dimethylpropyl)] nitroxide (SG1). The dispersion polymerization resulted in sub‐micron sized polymer particles and polymers of narrow polydispersity.

Five, six and seven-membered intramolecular aromatic substitutions of imidazol-5-yl radicals are reported using both metal hydride/AIBN and photochemical conditions to give imidazo[5,1-a]isoindole, imidazo[5,1-a]isoquinoline and imidazo[5,1-a]benzazepine. Procedures for the synthesis of 5-bromo-(N-ω- phenylalkyl)imidazole radical precursors using 1,3-dibromo-5,5-dimethylhydantoin (dibromantin) and Nbromosuccinimide (NBS) are given.

Summary: Macromonomers have been prepared by polymerization of acrylic acid (AA) and tert-butyl acrylate (tBA) in the presence of the addition-fragmentation chain transfer (AFCT) agents, ethyl α-(bromomethyl)acrylate (EBMA) and tert-butyl α-(bromomethyl)acrylate (BBMA). Chain transfer constants of 1.25 (EBMA) and 1.14 (BBMA) in the AA polymerization, and 2.42 (EBMA) and 1.75 (BBMA) in the tBA polymerization were obtained. The reduction in molecular weight with increasing concentration of AFCT agent and efficient introduction of 2‐carbalkoxy‐2‐propenyl ω‐end group was indicative of macromonomer formation. Polymerizations were retarded with increasing concentrations of AFCT agent and increases in the absolute concentration of EBMA slowed down the polymerization of AA but not tBA. The difference between EBMA and BBMA was less significant with tBA; more efficient macromonomer synthesis was indicated by less retardation and greater double bond retention at higher conversions. Copolymerizations of poly(AA) and poly(tBA) macromonomers with styrene indicated that the former was more reactive towards the St propagating radical. The results are rationalized in terms of the steric hindrance imposed by the tert‐butyl group. Poly(tBA) macromonomer was successfully hydrolyzed to give an alternative route to the poly(AA) macromonomer.Reaction mechanism for macromonomer synthesis using AFCT.

Summary:A detailed investigation of chain transfer to polymer during free radical ring‐opening polymerization of the eight‐membered disulfide monomer 2‐methyl‐7‐methylene‐1,5‐dithiacyclooctane (MDTO) is presented. It has been shown that extensive chain transfer to polymer occurs involving both poly(MDTO) radicals and cyanoisopropyl radicals. Significant decreases in molecular weight were observed when cyanoisopropyl radicals were generated in the presence of poly(MDTO) in the absence of monomer. The molecular weight distribution (MWD) obtained from polymerization of MDTO in the presence of pre‐added poly(MDTO) was markedly different from that obtained without pre‐added polymer. A kinetic model was constructed in an attempt to quantitatively describe the chain transfer to polymer process based on the addition fragmentation chain transfer mechanism. It was found however that the simulated MWDs were considerably broader than the experimental MWDs, which were similar to the Schulz‐Flory distribution.

Summary:The controlled/living radical polymerizations of methyl acrylate in 50% v/v of an ionic liquid initiated by the alkoxyamine generated in situ from 4‐oxo‐2,2,6,6‐tetramethyl‐1‐piperidinyl‐N‐oxyl (4‐oxo‐TEMPO) and 2,2′‐azoisobutyronitrile (AIBN) at 140–155 °C are reported. The number‐average molecular weights increased linearly with conversion, and polydispersity indices are approximately 1.4 in the best case. The rates of polymerization were greater than in anisole, and similar to the rate of spontaneous polymerization in the ionic liquid.

Summary: The controlled/living radical polymerizations of methyl acrylate in 50% v/v of an ionic liquid initiated by the alkoxyamine generated in situ from 4-oxo-2,2,6,6-tetramethyl-1-piperidinyl-N-oxyl (4-oxo-TEMPO) and 2,2'-azoisobutyronitrile (AIBN) at 140–155 °C are reported. The number-average molecular weights increased linearly with conversion, and polydispersity indices are approximately 1.4 in the best case. The rates of polymerization were greater than in anisole, and similar to the rate of spontaneous polymerization in the ionic liquid. $\overline M _{\rm n}$ (filled symbols) and $\overline M _{\rm w} /\overline M _{\rm n}$ (open symbols) vs. conversion for the MA polymerization in the presence of [4-oxo-TEMPO]/[AIBN] (2.8:1) in 50% v/v anisole with 0.03 M AIBN (squares) and 50% v/v [hmim][PF6] with 0.03 M AIBN (circles), and 0.06 M AIBN (triangles).

The 2,6-spirodicyclohexyl substituted nitroxide, cyclohexane-1-spiro-2'-(3',5'-dioxo-4'-benzylpiperazine-1'-oxyl)-6'-spiro-1"-cyclohexane (BODAZ), was investigated as a mediator for controlled/living free-radical polymerization of styrene. The values of the number-average molecular weight increased linearly with conversion, but the polydispersities were higher than for the corresponding 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO) and 2,5-bis(spirocyclohexyl)-3-benzylimidazolidin-4-one-1-oxyl (NO88Bn) mediated systems at approximately 2.2 and 1.6 at 100 and 120 °C, respectively. These results were reflected in the rate coefficients obtained by electron spin resonance spectroscopy; at 120 °C, the values of the rate coefficients for polystyrene-BODAZ alkoxyamine dissociation (kd), combination of BODAZ and propagating radicals (kc), and the equilibrium constant (K) were 1.60 × 10⁻⁵ s⁻¹, 5.19 × 10⁶ M⁻¹ s⁻¹, and 3.08 × 10⁻¹² M, respectively. The value of kd was approximately one and two orders of magnitude lower, and that of K was approximately 20 and 7 times lower than for the NO88Bn and TEMPO adducts. These results are explained in terms of X-ray crystal structures of BODAZ and NO88Bn; the six-membered ring of BODAZ deviates significantly from planarity as compared to the planar five-membered ring of NO88Bn and possesses a benzyl substituent oriented away from the nitroxyl group leading to a seemingly more exposed oxyl group, which resulted in a higher kc and a lower kd than NO88Bn. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3892–3900, 2003

Styrene radical polymerizations mediated by the imidazolidinone nitroxides 2,5-bis(spirocyclohexyl)-3-methylimidazolidin-4-one-1-oxyl (NO88Me) and 2,5-bis(spirocyclohexyl)-3-benzylimidazolidin-4-one-1-oxyl (NO88Bn) were investigated. Polymeric alkoxyamine (PS-NO88Bn)-initiated systems exhibited controlled/living characteristics at 100–120 °C but not at 80 °C. All systems exhibited rates of polymerization similar to those of thermal polymerization, with the exception of the PS-NO88Bn system at 80 °C, which polymerized twice as quickly. The dissociation rate constants (kd) for the PS-NO88Me and PS-NO88Bn coupling products were determined by electron spin resonance at 50–100 °C. The equilibrium constants were estimated to be 9.01 × 10⁻¹¹ and 6.47 × 10⁻¹¹ mol L⁻¹ at 120 °C for NO88Me and NO88Bn, respectively, resulting in the combination rate constants (kc) 2.77 × 10⁶ (NO88Me) and 2.07 × 10⁶ L mol⁻¹ s⁻¹ (NO88Bn). The similar polymerization results and kinetic parameters for NO88Me and NO88Bn indicated the absence of any 3-N-transannular effect by the benzyl substituent relative to the methyl substituent. The values of kd and kc were 4–8 and 25–33 times lower, respectively, than the reported values for PS-TEMPO at 120 °C, indicating that the 2,5-spirodicyclohexyl rings have a more profound effect on the combination reaction rather than the dissociation reaction. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 327–334, 2003

The thiyl radicals derived from 2-mercaptoethanol and thiophenol were found to undergo a complex series of reactions with 1,1,3,3-tetramethyl-2,3-dihydroisoindol-2-yloxyl (TMIO). Thus, treatment of 2-mercaptoethanol with di-t-butyl peroxyoxalate (DTBPO) in the presence of TMIO produced two N–S compounds—a sulfoxamide and a sufonamide—not the expected N–O–S adduct. The reaction between thiophenol and TMIO, which proceeded at a reasonable rate in the absence of DTBPO, produced 1,1,3,3-tetramethyl-2,3-dihydroisoindolin and its corresponding phenylsulfoxamide, diphenyl disulfide, phenylsulfinic acid, and 1,1,3,3-tetramethyl-2,3-dihydroisoindol-2-ylphenylsulfonate (the adduct of TMIO and the phenylsulfonyl radical). The mechanism of formation of these products, and the use of TMIO for trapping S-centred radicals, are discussed. A new radical fragmentation process, which appears to be general for aminoxyl adducts of electron-rich systems, is described.

A new series of 1,1,3,3-tetraethylisoindoline-2-oxyl (TEISO)-based alkoxyamines was prepared. The half-lives for thermal dissociation indicated that the most sterically congested cumyl-TEISO alkoxymine had the greatest potential as an initiator for the polymerization of monomers at lower temperatures. The polymerization of styrene at 110 °C gave a linear evolution of Mn with conversion in the early stages. Further evidence for the “living” nature was given by the polydispersities of the polymers that remained low (Mw/Mn = 1.13–1.27) throughout the polymerization (up to 80% conversion). No polymer was formed for the styrene system in a reasonable time below 100 °C. High-performance liquid chromatographic/mass spectrometric investigations of the distribution of trapped oligomers containing one to nine monomer units formed at 60 °C revealed that the trapping of oligomeric cumyl–styryl radicals by TEISO is irreversible at this temperature. Methyl methacrylate polymerized with cumyl-TEISO at 60–70 °C, although the initial high rates of polymerization soon decreased to zero at low conversions (10–15%), and the high polydispersities (Mw/Mn = 1.42–1.73) indicated significant side reactions. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1232–1241, 2001

Oxidative radical cyclisation using Bu 3SnH has been used for the synthesis of [1,2-c]-fused imidazoles and [1,2-a]-fused pyrroles from imidazolecarbaldehydes and acylpyrroles respectively. The intermediate nucleophilic N-alkyl radicals cyclise onto imidazole and pyrrole rings followed by oxidative re-aromatisation.

A new protocol for the synthesis of [1, 2-a]-fused benzimidazoles and imidazoles has been developed using intramolecular homolytic aromatic substitution via ω-alkyl radicals generated from 1-(ω-benzeneselenylalkyl)- 2-(benzenesulfenyl)-benzimidazoles and -2-(p-toluenesulfonyl)imidazoles.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

For Abstract see ChemInform Abstract in Full Text.

For Abstract see ChemInform Abstract in Full Text.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.