Investigation of thiol‐ene addition reaction on poly(isoprene) under UV irradiation: Synthesis of graft copolymers with “V”‐shaped side chains

Poly(isoprene) (PI) with pendant functional groups was successfully synthesized by thiol‐ene addition reaction under 365 nm UV irradiation, and the functionalized PI was further modified and used to prepare graft copolymers with “V”‐shaped side chains. First, the pendant ? SCH₂CH(OH)CH₂OH groups were introduced to PI by thiol‐ene addition reaction between 1‐thioglycerol and double bonds, and the results showed that the addition reaction carried out only on double bonds of 1,2‐addition isoprene units. After the esterification of hydroxyl groups by 2‐bromoisobutyryl bromide, the forming macroinitiator was used to initiate the atom transfer radical polymerization (ATRP) of styrene (St) and tert‐butyl acrylate (tBA), and the graft copolymers PI‐g‐PS ₂ and PI‐g‐PtBA ₂ or PI‐g‐PAA ₂ (by hydrolysis of PI‐g‐PtBA ₂) were obtained, respectively. It was confirmed that the graft density of side chains on PI main chains could be easily controlled by variation of the contents of modified 1,2‐addition isoprene units on PI. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3797–3806, 2010     

Absolute Rate Constants for the Addition of the 1‐(tert‐Butoxy)carbonylethyl Radical onto Cyclic Alkenes in Solution

Absolute rate constants are reported for the addition of the 1‐[(tert‐butoxy)carbonyl]ethyl (= 2‐(1,1‐dimethylethoxy)‐1‐methyl‐2‐oxoethyl) radical ^.CHMeCO₂(t‐Bu) to several cyclic and monosubstituted alkenes in MeCN as obtained by time‐resolved electron paramagnetic resonance (EPR). The activation energies for the addition of this alkyl radical are mainly governed by the addition enthalpy but are also substantially lowered by the ambiphilic effect and by relief of cyclic strain.     

A New Synthesis of Optically Active 3‐Substituted (3S)‐3,4‐Dihydro‐5‐(perfluoroalkyl)‐2H‐[1,4]oxazepin‐7‐ones

Optically active (perfluoroalkyl)‐oxazepin‐7‐ones were synthesized in two steps starting from ethyl perfluorobut‐2‐ynoate by direct addition of optically active amino alcohols via intermolecular Michael addition and lactone formation.     

The influence of cross-linking agents on ring-opening metathesis polymerized thermosets

The addition of suitable cross-linking agents with norbornene-based monomers has significant effects on the thermal properties of the resulting polymers formed by olefin metathesis. Ethylidene norbornene (ENB) and endo-dicyclopentadiene (endo-DCPD) were mixed separately with various loadings of three different cross-linking agents and then polymerized with the addition of Grubbs’ catalyst. The polymerization kinetics and resulting glass transition temperature (T _g) of the systems were evaluated by differential scanning calorimetry (DSC). The addition of the first cross-linking agent, norbornadiene (CL-1), to both endo-DCPD and ENB resulted in decreasing glass transition temperatures with increasing concentrations. In contrast, the addition of the other two cross-linking agents (CL-2 and CL-3), which were both custom synthesized bifunctional norbornyl systems, to both endo-DCPD and ENB resulted in a monotonic increases in T _g with cross-linker concentration. By tailoring the loading of these custom cross-linking agents, the properties of these polymer systems can be controlled for various applications, including self-healing composites.     

Rapid Synthesis of Alkoxyamine Hydrochloride Derivatives from Alkyl Bromide and N,N′-Di-tert-butoxycarbonylhydroxylamine [(Boc)2NOH]

The conventional route to alkoxyamine hydrochloride derivatives is by reaction of alkyl bromides with N-hydroxyphthalimide or N-hydroxysuccinimide followed by addition of hydrazine and HCl. Transformation of an alkyl bromide to the corresponding alkoxyamine hydrochloride can be accomplished more rapidly in good yields without using hazardous hydrazine by reaction of (Boc)₂NOH (N,N′-di-tert-butoxycarbonylhydroxylamine) and alkyl bromide followed by addition of HCl. Alkoxyamine hydrochlorides are powerful reagents in organic synthesis that can be used to synthesize alkoxyimino derivatives after condensation with a ketone or aldehyde.     

Reversal of the Stereochemical Course of 1‐Methyl‐1H‐indole Addition to Cinnamaldehyde with cis‐5‐Benzyl‐(2‐fluoromethyl)‐2,3‐dimethylimidazolidin‐4‐ones as Catalysts – a Puzzling ‘Fluorine Effect’

Replacement of the cis‐Me group by CH₂F in the imidazolidinone organocatalyst specified in the title (so‐called McMillan generation‐I catalyst) leads to reversal of the product configuration in the title reaction. The topicity reversal in the nucleophilic addition step must arise either from cis‐addition with respect to the benzylic substituent of an (E)‐iminium ion intermediate or from trans‐addition to the corresponding (Z)‐iminium ion. Mechanistic investigations have not provided evidence for either one of these two possibilities, so far.     

Facile Synthetic Method for the Preparation of Dithioacetals by the Double Conjugate Addition of Acetylenes Bearing Electron-Withdrawing Groups with Thiols

β, β-Bis(alkylmercapto)propionates were obtained by the reaction of methyl propiolates with 2 equiv. of mercaptanes in the presence of tri-n-butylphosphine in high yield. The corresponding dithioacetals could be also obtained by the conjugate addition of mercaptanes toward methyl β-alkylmercaptoenoates, in which, tri-n-butylphosphine also catalyzed the addition of thiols.     

A novel reverse worm-like micelle from a lecithin/sucrose fatty acid ester/oil system

We report a novel method for forming reverse worm-like micelles in nonpolar organic solvents. This method requires the addition of trace amounts of a sucrose fatty acid ester (SFE), in addition to lecithin and a nonpolar organic solvent. The region in which these micelles formed increased with lecithin concentration and hydrophobicity of SFE. In addition, zero-shear viscosity (η ₀) of the reverse worm-like micelles increased rapidly upon addition of SFE, reaching 1–3 million times the viscosity of n-decane. Furthermore, the change in η ₀ was examined in detail by performing dynamic viscoelasticity measurements. Results showed that the η ₀ of solution increased upon addition of SFE because both the length and number of reverse worm-like micelles increased along with SFE concentration.     

Visible-Light-Induced ortho-Selective Migration on Pyridyl Ring: Trifluoromethylative Pyridylation of Unactivated Alkenes

The photocatalyzed ortho-selective migration on a pyridyl ring has been achieved for the site-selective trifluoromethylative pyridylation of unactivated alkenes. The overall process is initiated by the selective addition of a CF₃ radical to the alkene to provide a nucleophilic alkyl radical intermediate, which enables an intramolecular endo addition exclusively to the ortho-position of the pyridinium salt. Both secondary and tertiary alkyl radicals are well-suited for addition to the C2-position of pyridinium salts to ultimately provide synthetically valuable C2-fluoroalkyl functionalized pyridines. Moreover, the method was successfully applied to the reaction with P-centered radicals. The utility of this transformation was further demonstrated by the late-stage functionalization of complex bioactive molecules.     

Dicarboxylates of 3-Methylidene-β-lactams: Addition Reactions to the Exocyclic Double Bond,Formation of Spiro-β-lactams,and Reductive Ring Opening by Hydrazines

O-, S-, and N-Nucleophiles are added to the exocyclic double bond of the title compounds 1 . The addition of O- or S-nucleophiles yields stable products (Scheme 1), while addition of N-nucleophiles results in thermally labile compounds (Scheme 2). The reaction is studied by spectroscopic methods. From hydrazine adducts, a spiro[azetidine-3,3′-pyrazolidine] 7 is obtained, and the addition products of methyl- and benzylhydrazine rearrange to pyrazol-4-carboxylates 6 . Furthermore, the exocyclic double bond is used for the formation of spiro-β-lactams either by cyclopropane formation or by Diels-Alder reactions (Scheme 4). The steric course of all reactions is studied, and it is shown that all reactions with the double bond occur from the side opposite to the bulkier substitutent at C(4) of the β-lactam ring.     

Synthesis of Glycosyl Azides by the Addition of Phenylselenenyl Azide to Glycals

Abstract

The addition of phenylselenenyl azide to glycals is carried out under conditions that give 2-deoxy-2-phenylselenoglycosyl azides. This regiochemistry is opposite to that obtained under free-radical conditions, which are known to produce 2-azido-2-deoxyselenoglycosides. The addition reaction is carried out with phenylselenenyl chloride and sodium azide in dimethylformamide, and is stereoselective for trans addition. Tri-O-benzyl-d-glucal and di-O-benzyl-l-rhamnal each gave two addition products, in which the phenylselenyl and azido groups were either trans diaxial or trans diequatorial. Tri-O-benzyl-d-galactal gave only the trans diaxial addition product.     

Symmetrie und analytische Struktur der Additionstheoreme räumlicher Funktionen und der Mehrzentren-Molekülintegrale über beliebige Atomfunktionen

Three-dimensional functions f(r) = g(r) · Y _m ^l (, ø), which transform like an irreducible tensor, are transformed simultaneously under rotations and translations. The relationships governing the transformation reveal some general properties. If the addition theorem of a function f(r) can be represented by a one-center expansion in terms of surface spherical harmonics Y _m ^l , each expansion coefficient is given by a Clebsch-Gordan coefficient and a radial function.Because of these properties, addition theorems are especially helpful for the simplification and evaluation of quantum-mechanical matrix elements and multi-center energy integrals in molecular LCAO calculations. The application of addition theorems has two major advantages: First, because addition theorems are equivalent to translation formulas, the number of centers of an integral can be reduced by translation of orbitals and operators. Second, due to the typical analytical structure of the series expansion representing the addition theorem, the dimensionality of a molecular integral can be reduced, because the integration over the angular variables can be executed. Then, a molecular multi-center integral is represented by a series of one-center integrals over functions of the radial variable only.

Herrn Professor Dr. H. Hartmann zum 65. Geburtstag gewidmet.     

Synthesis of photopolymers with pendant cyclic carbonate and cinnamic ester groups

Photopolymers with both pendant cyclic carbonate groups and cinnamic ester groups were synthesized by the addition reaction of poly(glycidyl methacryalte-co-styrene)[poly(GMA-co-AN)] with carbon dioxide and then with cinnamoyl chloride. Soluble quaternary ammonium salt catalysts showed good yield of cinnamoyl chloride addition to the glycidyl methacrylate groups. Quaternary salt catalysts of longer alkyl chain length and of more nucleophilic anion offered higher yield of cinnamoyl chloride addition. Photochemical reaction test showed that poly(CNMA-co-DOMA-co-St) had a good photosensitivity. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effect of Penicillin on Nitrite-Oxidizing Bacteria in Activated Sludge

The effects of penicillin G on the number and activity of nitrite-oxidizing bacteria were investigated in laboratory-scale reactors and batch tests. At a concentration of 100 mg L⁻¹, addition of penicillin G for short periods did not significantly affect nitrite oxidation, while addition for more than 2 months suppressed nitrite oxidation. Fluorescence in situ hybridization with 16S ribosomal RNA-targeted probes revealed a slight decrease in the abundance of Nitrospira, while Nitrobacter was not affected by addition of penicillin G for more than 39 days. The resistance of nitrite-oxidizing bacteria to penicillin appeared to be positively affected by intermittent aeration only when accompanied by denitrification; otherwise, the aeration mode (continuous or intermittent aeration) did not significantly affect the abundance of Nitrobacter and Nitrospira.     

Hydrogen bond network-stabilisation of blue phases by addition of a chiral N-(10-hydroxydecyl)succinimide derivative and alkane diols

Blue phases (BPs) obtained by doping a commercially available liquid crystalline compound (4-butyl-N-(4-ethoxybenzylidene)aniline (EBBA)) with (2R,3R)-2,3-bis(4-octyloxyphenylbenzoyloxy)-N-(hydroxydecyl)succinimide (1) were highly stabilised by the addition of a small amount of alkane diols. Especially, addition of only 0.5 mol% of octane-1,8-diol increased the BP–Iso transition temperature by 10 K and widened the BP temperature range up to 35 K. A model stabilisation mechanism based on the construction of a hydrogen bond network in each disclination zone in BPs was proposed.     

Kinetic elucidation of comonomer‐induced chemical and physical activation in heterogeneous ziegler‐natta propylene polymerization

We have kinetically elucidated the origins of activity enhancement because of the addition of comonomer in Ziegler‐Natta propylene polymerization, using stopped‐flow and continuously purged polymerization. Stopped‐flow polymerization (with the polymerization time of 0.1–0.2 s) enabled us to neglect contributions of physical phenomena to the activity, such as catalyst fragmentation and reagent diffusion through produced polymer. The propagation rate constant k_p and active‐site concentration [C*] were compared between homopolymerization and copolymerization in the absence of physical effects. k_p for propylene was increased by 30% because of the addition of a small amount of ethylene, whereas [C*] was constant. On the contrary, both k_p (for propylene) and [C*] remained unchanged by the addition of 1‐hexene. Thus, only ethylene could chemically activate propylene polymerization. However, continuously purged polymerization for 30 s resulted in much more significant activation by the addition of comonomer, clearly indicating that the activation phenomenon mainly arises from the physical effects. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Highly Diastereo‐ and Enantioselective Michael Addition of Nitroalkanes to 2‐Enoyl‐Pyridine N‐Oxides Catalyzed by Scandium(III)/Copper(II) Complexes

A C₂‐symmetric Schiff‐base ligand, derived from tridentate‐Schiff‐base, was developed and successfully applied to the asymmetric Michael addition of nitroalkanes to 2‐enoyl‐pyridine N‐oxides. With this newly catalytic system, an unprecedented diastereoselectivity was obtained in the asymmetric Michael addition of nitroalkanes to 2‐enoyl‐pyridine N‐oxides. In addition, a switch in enantioselectivity was achieved by using this newly catalytic system and our previous catalyst. After a facile reduction, the optically active adduct was converted to a biologically active dihydro‐2H‐pyrrol 4 a . Furthermore, a connection of two tridentate‐Schiff‐base subunits proved to be an effective strategy in ligand design.     

Rhodium Fluoroapatite Catalyzed Conjugate Addition of Arylboronic Acids to α,β‐Unsaturated Carbonyl Compounds

Rhodium fluoroapatite (RhFAP) is an efficient catalyst for conjugate addition of organoboron reagents to α,β‐unsaturated carbonyl compounds. A variety of arylboronic acids and α,β‐unsaturated carbonyl compounds were converted to the corresponding conjugate‐addition products, demonstrating the versatility of the reaction. The reaction is highly selective. RhFAP was recovered quantitatively by simple filtration, and reused for four cycles.     

Synthesis of pyrazolo[1,5-a]pyridines and pyrazolo[1,5-c]pyrimidines by reaction of heterocyclic amidrazones with 1,3-dicarbonyl compounds

1,3-Dicarbonyl compounds 2 react with 1-amino-2(1H)-pyridin-2-imines or 1-amino-2(1H)-pyrimidin-2-imines 1 giving new pyrazolo[1,5-a]pyridines or pyrazolo[1,5-c]pyrimidines 5 respectively by addition, oxidation and condensation. Isolation of an intermediate 3 shows that surprisingly the addition of the CH acidic 1,3 -dicarbonyl compound to position 6 of the pyrimidine 1 is the initial step.     

The reaction of N-aminophthalimide with isothiocyanates

N-Aminophthalimide ( I ) reacted in refluxing isopropyl alcohol with a number of isothiocyanates to give the related 1:1 addition products, N-(3-substitutedthioureido)phthalimides III. On the other hand, heating I directly with an excess of neat arylisothiocyanates produced the N-arylphthalimides IV. As shown for IIIa, the 1:1 addition products are conveniently deblocked by the Ing-Manske procedure to yield the 4-substituted thiosemicarbazide.