Low-frequency Raman spectra of odd α,ω-disubstituted n-alkanes

Low-Frequency Raman spectra of odd α,ω-dibromo- and α,ω-dihydroxy-n-alkanes were recorded. The longitudinal acoustic mode (LAM-1) frequencies were assigned by references to the published results for n-alkanes and even α,ω-disubstituted n-alkanes and also by taking account of the effects of end intermolecular forces and end-group masses by use of the chain model of Minoni and Zerbi.     

Preparation and thermal degradation of α,ω-alkylene bis[5-(1,2,3,4-thiatriazolyl)] sulfides

Syntheses of some extremely shock sensitive α,ω-alkylene bis[ 5-(1,2,3,4-thiatriazolyl)] sulfides via reaction of sodium 1,2,3,4-thiatriazoline thionate (1) and α,ω-dihaloalkanes are described. Dichloromaleic imide reacted analogously with 1 to give 3,4-bis(5-(1,2,3,4-thiatriazolyl)thio)maleic imide. The compounds decompose thermally in solution with formation of α,ω-alkylene bis(thio-cyanates), nitrogen and sulfur. The infrared spectra are discussed.     

Study of the synthesis of poly(isobutylene-b-amide-11) by polycondensation of α,ω-dianhydride oligoisobutylene with α,ω-diamino oligoamide-11. I. Study of amine–anhydride and amide–anhydride reactions on low molecular weight models and on oligomers and polymers

The side reactions connected with the polycondensation of α,ω-diamino oligoamides and α,ω-dianhydride oligoisobutylenes are studied on low and high molecular weight models. Models for amine and anhydride end groups are dodecylamine and (2-dodecene-1-yl) succinic anhydride, respectively; their reaction is studied in the bulk (170°C) and in solution (142, 152, and 162°C); the products are analyzed by ¹H-, ¹³C-, and ¹H-¹³C-NMR and GPC. Some of these products and the junctions between the blocks are prepared independently. Models of amide groups in the chain are N-dodecyldodecanamide and N-dodecyloctadecanamide; their reaction with anhydride model results in cleavages with formation of imide groups. The results obtained from low molecular weight models are confirmed by studies on oligomers. They show unambiguous by that crosslinking which accompanies the block polycondensation originates from the reaction of amino-end groups with the intermediary acid groups resulting from the amine-anhydride reaction.     

A convenient synthesis of α,α′‐ homo‐ and α,α′‐hetero‐bifunctionalized poly(ε‐caprolactone)s by ring opening polymerization: The potentially valuable precursors for miktoarm star copolymers

Two new ring opening polymerization (ROP) initiators, namely, (3‐allyl‐2‐(allyloxy)phenyl)methanol and (3‐allyl‐2‐(prop‐2‐yn‐1‐yloxy)phenyl)methanol each containing two reactive functionalities viz. allyl, allyloxy and allyl, propargyloxy, respectively, were synthesized from 3‐allylsalicyaldehyde as a starting material. Well defined α‐allyl, α′‐allyloxy and α‐allyl, α′‐propargyloxy bifunctionalized poly(ε‐caprolactone)s with molecular weights in the range 4200–9500 and 3600–10,900 g/mol and molecular weight distributions in the range 1.16–1.18 and 1.15–1.16, respectively, were synthesized by ROP of ε‐caprolactone employing these initiators. The presence of α‐allyl, α′‐allyloxy and α‐allyl, α′‐propargyloxy functionalities on poly(ε‐caprolactone)s was confirmed by FT‐IR, ¹H, ¹³C NMR spectroscopy, and MALDI‐TOF analysis. The kinetic study of ROP of ε‐caprolactone with both the initiators revealed the pseudo first order kinetics with respect to ε‐caprolactone consumption and controlled behavior of polymerization reactions. The usefulness of α‐allyl, α′‐allyloxy functionalities on poly(ε‐caprolactone) was demonstrated by performing the thiol‐ene reaction with poly(ethylene glycol) thiol to obtain (mPEG)₂‐PCL miktoarm star copolymer. α‐Allyl, α′‐propargyloxy functionalities on poly(ε‐caprolactone) were utilized in orthogonal reactions i.e copper catalyzed alkyne‐azide click (CuAAC) with azido functionalized poly(N‐isopropylacrylamide) followed by thiol‐ene reaction with poly(ethylene glycol) thiol to synthesize PCL‐PNIPAAm‐mPEG miktoarm star terpolymer. The preliminary characterization of A₂B and ABC miktoarm star copolymers was carried out by ¹H NMR spectroscopy and gel permeation chromatography (GPC). © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 844–860     

Neuartige massenspektrometrische Zerfallsreaktionen bei α,ω-disubstituierten Alkanen. 15. Mitteilung über das massenspektrometrische verhalten von stickstoffverbindungen [1]

The mass spectral behaviour of α,ω-disubstituted alkanes and, especially, that of different N-substituted α,ω-diaminoalkanes has been investigated. It was found that the two amino groups which are separated by CH₂-groups can fragment only to a small extent indepently from each other. Yet those fragmentation reactions are predominant in which both functional groups participate. The main reactions of this type are:

• 1 Loss of the N-substituent (R) from the molecular ion, leading to the [M⁺—R]-ions.
• 2 Loss of NH₃, primary or secondary amines from the [M⁺—R]-ion in the case of monodi-, tri- and tetra-substituted diamino compounds respectively.
• 3 α-Cleavage to the non charged nitrogen atom by forming the ions
• 4 S_Ni-type fragmentation.

The mechanisms of these fragmentation patterns were deduced by using D-labelled derivatives, from metastabile peaks and high resolution mass spectrometry. These reactions seem to be typical for disubstituted alkanes.     

Block copolymer from α,ω-dihydroxyl polystyrene and polyethylene glycol

α,ω-Dihydroxyl polystyrene was synthesized by the addition of styrene oxide to polystyryl dianion initiated with sodium naphthalene. Diglyme was found to be an unsuitable solvent for the preparation of low molecular weight compounds. Block copolymerization of the α,ω-dihydroxyl polystyrenes (M?_n = 2250, 3140, and 6200) with poly(ethylene glycols) (M?_n = 404, 1960, and 5650) was pursued by introducing urethane linkages with 4,4′-diphenylmethane diisocyanate. The mechanical, thermal, and viscoelastic properties, solution viscosity, molecular weight distribution, and moisture absorption of the block copolymers obtained were examined. Incorporation of styrene blocks was found to disturb the crystallization and fusion of poly(ethylene glycol) blocks. Films cast from benzene solution were soft and elastic and absorbed up to 5.8% moisture.     

Synthesis of β‐Haloketones by β‐Addition Reactions of α,β‐Unsaturated Ketones with BX3 (X = Br,Cl) as Halide Source

A series of β‐bromoketones and β‐chloroketones were synthesized by the addition reactions of α,β‐unsaturated ketones under BX₃ (X = Br, Cl) and ethylene glycol reaction system. The α,β‐unsaturated ester also was successfully converted to its corresponding β‐bromoester under the reaction condition.     

Fluorinated β-Sultones

Fluorinated (β)-sultones are formed on addition of sulfur trioxide to fluorinated olefins. Tetrafluoroethanesultone has been studied particularly thoroughly. The title compounds are characterized by the ease with which they undergo ring cleavage to give, e.g., derivatives of α-sulfo carboxylic acids, of sulfonic acids, of carboxylic acids, and of sulfuric acid. Fluorinated compounds of this type containing an α-hydrogen atom are especially valuable in preparative work.     

Synthesis of block copolymer with polystyrene and nylon units

Bis-ε-aminocaproylaminocaproylhexamethylenediamine ( I ) was synthesized as an analog of 6-nylon pentamer diamine, and its incorporation into block copolymers was studied with the use of α,ω-dihydroxyl, α,ω-bisdimethylchlorosilyl, and α,ω-diepoxy polystyrene. In the course of the experiments, the stability and the reactivity of 4,4′-diphenylmethane diisocyanate and tetramethylene diisocyanate in aprotic dipolar solvents were examined by infrared spectroscopy. The only usable solvent, N-methylpyrrolidone, was found still inadequate for the synthesis involving I, diisocyanate, and α,ω-dihydroxyl polystyrene. A block copolymer having M _n = 18,000 was obtained by the reaction of I and α,ω-diepoxy polystyrene. All T_g values of the block copolymers were above 90°C, higher than for polystyrenes with corresponding molecular weight.     

Catalytic Asymmetric 1,2‐Addition of α‐Isothiocyanato Phosphonates: Synthesis of Chiral β‐Hydroxy‐ or β‐Amino‐Substituted α‐Amino Phosphonic Acid Derivatives

α‐Amino phosphonic acid derivatives are considered to be the most important structural analogues of α‐amino acids and have a very wide range of applications. However, approaches for the catalytic asymmetric synthesis of such useful compounds are very limited. In this work, simple, efficient, and versatile organocatalytic asymmetric 1,2‐addition reactions of α‐isothiocyanato phosphonate were developed. Through these processes, derivatives of β‐hydroxy‐α‐amino phosphonic acid and α,β‐diamino phosphonic acid, as well as highly functionalized phosphonate‐substituted spirooxindole, can be efficiently constructed (up to 99 % yield, d.r. >20:1, and >99 % ee). This novel method provides a new route for the enantioselective functionalization of α‐phosphonic acid derivatives.     

Hydrolytic degradation of poly(ε‐caprolactone) with different end groups and poly(ε‐caprolactone‐co‐γ‐butyrolactone): characterization and kinetics of hydrocortisone delivery

Asymmetric telechelic α‐hydroxyl‐ω‐(carboxylic acid)‐poly(ε‐caprolactone) (HA‐PCL), α‐hydroxyl‐ω‐(benzylic ester)‐poly(ε‐caprolactone) (HBz‐PCL), and an asymmetric telechelic copolymer α‐hydroxyl‐ω‐(carboxylic acid)‐poly(ε‐caprolactone‐co‐γ‐butyrolactone) (HA‐PCB) were synthesized by ring‐opening polymerization of ε‐caprolactone (CL). CL and CL/γ‐butyrolactone mixture were used to obtain homopolymers and copolymer respectively at 150°C and 2 hr using ammonium decamolybdate (NH₄) [Mo₁₀O₃₄] (Dec) as a catalyst. Water (HA‐PCL and HA‐PCB) or benzyl alcohol (HBz‐PCL) were used as initiators. The three polylactones reached initial molecular weights between 2000 and 3000 Da measured by proton nuclear magnetic resonance (¹H‐NMR). Compression‐molded polylactone caplets were allowed to degrade in 0.5 M aqueous p‐toluenesulfonic acid at 37°C and monitored up to 60 days for weight loss behavior. Data showed that the copolymer degraded faster than the PCL homopolymers, and that there was no difference in the weight loss behavior between HA‐PCL and HBz‐PCL. Caplets of the three polylactones containing 1% (w/w) hydrocortisone were placed in two different buffer systems, pH 5.0 with citrate buffer and pH 7.4 with phosphate buffer at 37°C, and monitored up to 50 days for their release behavior. The release profiles of hydrocortisone presented two stages. The introduction of a second monomer in the polymer chain significantly increased the release rate, the degradation rate for HA‐PCB being faster than those for HBz‐PCL and HA‐PCL. At the pH studied, only slight differences on the liberation profiles were observed. SEM micrographs indicate that hydrolytic degradation occurred mainly by a surface erosion mechanism. Copyright © 2009 John Wiley & Sons, Ltd.     

Regioselective hydrosilations. I. The hydrosilation of α,ω-dihydrogen functional oligopolydimethylsiloxanes with 3-vinyl-7-oxabicyclo[4.1.0]heptane

The hydrosilation of α,ω-dihydrogen functional oligopolydimethylsiloxanes with epoxy compounds containing vinyl groups has been found to take place regioselectively in such a manner that compounds can be isolated in high yields in which only one Si? H group has been reacted. Three different α,ω-dihydrogen functional oligopolydimethysiloxanes with different chain lengths were monohydrosilated and the resulting epoxide monomers characterized. The rate of hydrosilation at the first Si? H functional group has been shown to be considerably faster than at the second site and from these kinetic studies, activation energies for each hydrosilation step were calculated. Mechanisms are considered which offer an explantion for these observations. © 1993 John Wiley & Sons, Inc.     

Ammoniakverlust aus α,ω-Alkandiaminen im Massenspektrometer. 22. Mitteilung über das massenspektrometrische Verhalten von Stickstoffverbindungen

Loss of ammonia from α,ω-alkanediamines in the mass spectrometer . Under electron impact α,ω-alkanediamines lose ammonia from the molecular ion. This fragmentation reaction is explained in the case of 1.4-butanediamine ( 1 ) on the basis of the spectra of homologues and deuteriated derivatives. The reaction proceeds via neighbouring group participation; the mechanism is given in Scheme 1.     

A Mild Isomerization Reaction for β,γ‐Unsaturated Ketone to α,β‐Unsaturated Ketone

A series of β,γ‐unsaturated ketones were isomerized to their corresponding α,β‐unsaturated ketones by the introduction of DABCO in iPrOH at room temperature. The endo‐cyclic double bond (β,γ‐position) on ketone was rearranged to exo‐cyclic double bond (α,β‐position) under the reaction conditions.     

Studies on the Mass Spectra of N‐Aryl α,β‐Unsaturated γ‐Lactams

The mass spectra of a series of N‐aryl α,β‐unsaturated γ‐lactams were studied. Besides the molecular ion, the three characteristic fragments such as [M⁺‐29], [M⁺‐55], and [M⁺‐82] were commonly found in a series of N‐Aryl α,β‐unsaturated γ‐lactams in EI/MS. Further more the mechanism for the interpretation of these fragments is also de scribed.     

Preparation,characterization and properties of β-chitin and N-acetylated β-chitin

Free amino groups in β-chitin from squid pen were acetylated to obtain N-acetylated β-chitin. After careful control of degree of acetylation, thermal and mechanical properties of β-chitin and N-acetylated β-chitin were compared. The structural differences of β-chitin and N-acetylated β-chitin were characterized by Fourier transform infrared (FTIR) and wide-angle x-ray diffraction (WAXD) analysis. The results indicated that the crystallinity of N-acetylated β-chitin was higher than that of β-chitin and N-acetylated β-chitin exhibited characteristics similar to α-chitin. Equilibrium water content (EWC) of β-chitin reached to about 50% and this hydrophilic nature was assumed to be caused by a relatively weak hydrogen bonding force of β-chitin with parallel main chains. On the other hand, EWC of N-acetylated β-chitin was 40% due to the introduction of ordered structure. β-chitin and N-acetylated β-chitin have the tensile strength of 0.4 and 0.7 Mpa in the swollen state, respectively. Viscoelastic properties and thermal relaxation behaviors were investigated by dynamic mechanical thermal analysis (DMTA). DMTA spectra of these samples showed that α-transition peaks of β-chitin and N-acetylated β-chitin were observed at 170 and 190°C, respectively. These relaxation peak maxima were assigned to be their glass transition temperature. In addition, a second relaxation peak of β-chitin resulting from acetamide groups was found at 112°C and a broad relaxation peak of N-acetylated β-chitin at around 81–100°C. As a result of thermogravimetric analysis, 10% weight loss temperatures of β-chitin and N-acetylated β-chitin were 270 and 285°C, respectively. © 1996 John Wiley & Sons, Inc.     

Ultrasound Promoted 1, 3-Dipolar Cycloaddition Reactions of Nitrile Oxides with α, β-Unsaturated Acetals

The 1,3-dipolar cycloaddition reactions of nitrile oxides and α,β-unsaturated 1,3-dioxolanes were effectively accelerated by ultrasound irradiation to give the A²-isoxazolines with yields and regioselectivities surpassing those of the corresponding thermal reactions.     

Sulfur-containing optically active polymers. V. Synthesis and chiroptical properties of optically active poly(γ-ketosulfide)s prepared by polyaddition of 1,3-dimercaptobenzene to 4,4-dimethyl-2,5-cyclohexadien-1-one or to trans,trans-2,5-heptadien-3-one in the presence of chiral amines

Optically active poly(γ-ketosulfide)s having the asymmetric centers disposed along the main chain have been prepared by step polyaddition of 1,3-dimercaptobenzene to 4,4-dimethyl-2,5-cyclohexadiene-1-one, or to trans, trans-2,5-heptadiene-3-one, in the presence of catalytic amounts of chiral amines. The extent of asymmetric induction on the resulting polymeric product is found to be higher when the alicyclic ketone reagent is employed and is enhanced by lowering the catalyst concentration. The comparison of stereochemical features and chiroptical properties of appropriate low molecular weight analogues with those of the polymeric derivatives indicates that a comparable asymmetric induction occurs in polymers and model compounds, and that the former systems do not display appreciable evidence of ordered secondary structures, in agreement with a low stereoregularity degree along the macromolecular backbone. © 1996 John Wiley & Sons, Inc.     

Chemistry and Biochemistry of Microbial α-Glucosidase Inhibitors

α-Glucosidases are among the most important carbohydrate-splitting enzymes. They catalyze the hydrolysis of α-glucosidic linkages. Their substrates are—depending on their specificity—oligo- and polysaccharides. Microbial inhibitors of α-amylases and other mammalian intestinal carbohydrate-splitting enzymes studied during the last few years have aroused medical interest in the treatment of metabolic diseases such as diabetes. Moreover, they extend the spectrum of microbial secondary metabolites which comprises an enormous variety of structures. They also contribute considerably to a better understanding of the mechanism of action of α-glucosidases. These inhibitors belong to different classes of substances. Those studied most thoroughly are microbial α-glucosidase inhibitors which are members of a homologous series of pseudooligosaccharides of the general formula (4). They all have a core in common which is essential for their inhibitory action, a pseudodisaccharide residue consisting of an unsaturated cyclitol unit, and a 4-amino-4,6-dideoxy- glucose unit. The—in many respects—most interesting representative of this homologous series is acarbose (5), a pseudotetrasaccharide exhibiting a very pronounced inhibitory effect on intestinal α-glucosidases such as sucrase, maltase and glucoamylase. The present paper will review this new field of microbial α-glucosidase inhibitors which has been studied with particular intensity during the past ten years.     

Nitriles in Heterocyclic Synthesis: Reactivity of 2‐(Benzothiazol‐2‐ylmethyl)‐1,3‐thiazol‐4(5H)‐one towards α,β‐Unsaturated Nitriles

The reaction of 2‐(benzothiazol‐2‐ylmethyl)‐1,3‐thiazol‐4(5H)‐one 1 with α,β‐cinnamonitrile derivatives 2a‐n have been reported.