Reaction of 2,3-dichloro-5,6-dicyanopyrazine with enamines and some tertiary amines

The reaction of 2,3-dichloro-5,6-dicyanopyrazine ( 1 ) with enamines as well as a few tertiary amines as enamine precursors was investigated. Both reactions gave aminovinyl-substituted pyrazine derivatives. During the attempted purification of 3c or 3d by column chromatography on silica gel, 2-chloro-5,6-dicyano-3-(1′-oxocyclopent-2′-yl)pyrazine ( 4 ) was obtained, apparently by hydrolytic cleavage. The products prepared are all of interest as potential pesticides.     

Effects of polyethylene spacer length in polymeric electrolytes on gelation of ionic liquids and ionogel properties

Polymer electrolytes containing N,N′-(trans-cyclohexane-1,4-diyl)dibenzamide linkages, polyethylene ((CH₂)_m, m = 2, 4, 10) spacers, and bis(trifluoromethanesulfonyl)amide (TFSA) or bis(fluorosulfonyl)amide (FSA) counteranions (polymer abbreviation: CDBAm•X; m = 2, 4, 10; X = TFSA, FSA) have been synthesized, adding to our previous report (m = 6). In addition, their ability to effect the gelation of six ionic liquids and the properties of the resulting ionogels have been examined. The polymers, except for CDBA10•TFSA, effect the gelation for all ionic liquids used in this study at fairly low concentrations (0.9–50 g/L). Ionogel ionic conductivity is not dependent on the spacer length, but does decrease slightly as increasing amounts of the gelatinizer are introduced. In contrast to ionic conductivity, the temperatures at which these ionogels transition into isotropic fluids is dependent on the spacer length; the gel composed of [EMI][FSA] and 100 g/L of CDBA6•FSA transforms at 120 °C, while the gel composed of [EMI][FSA] and 5 g/L of CDBA2•FSA does not transform into a sol even when temperatures become 155 °C. In brief, ionogel heat resistance can be improved by changing the spacer length of the polyelectrolyte. Finally, it has been determined using cyclic voltammetry that the potential window of the polyelectrolytes is particularly wide, ranging from −1.6 to 2.5 V. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 249–255     

Neomacrophorin I,II, and III,novel drimenyl cyclohexanes with hydroxylated butanoates from Trichoderma sp. 1212-03

Neomacrophorins I (1), II (2), and III (3) were isolated from the culture broth of Trichoderma sp. 1212-03, which was collected at Shirakami Mountainous area in Japan. Structural analyses disclosed that these resemble known macrophorins but possess axial-hydroxy group at C3 as well as different side chains at C7′. These are diastereomeric forms of macrophorins for 5′,6′-epoxide functionality. The NMR analyses suggested their relative configurational relationship between the C1–C15 drimene and C1′–C7′ epoxyquinone moieties. ECD spectral discussions verified them particularly for C5′,C6′-epoxyquinone (1), C5′,C6′-epoxysemiquinone (2 and 3), and 2″,3″-dihydroxybutanoate moiety in 1 and 2. The configuration of C3″-stereocenter of 3 was determined by chiral GC–MS after converting into methyl (S)-3″-hydroxybutanoate by basic of 3 methanolysis. Biological assays disclosed that 1 induces hyphal branching of Cochliobolus miyabeanus as well as cytotoxicity against human colorectal cancer COLO 201.     

Cationic amylopectin derivatives as additives for analysis of proteins in capillary electrophoresis

Positively charged amylopectin, which is a major constituent of cationic starch, was used to modify the inner surface of fused-silica capillaries by addition to the running solution, which was subsequently employed in CE. Capillaries filled with cationic amylopectin derivatives were shown to generate a stable reversed EOF in the investigated range of pH 4-8. Among the additives studied, quaternary ammonium amylopectin derivatives with high amino and low hydroxypropyl groups showed fast electroosmotic mobility and very effectively suppressed the adsorption of proteins. The run-to-run and batch-to-batch repeatability of the procedures were satisfactory with RSDs of 0.5% and 2.4%, respectively. A basic protein, alpha-chymotrypsinogen, migrated within 6 min and the theoretical plate number of it reached 560 000 plates/m.     

Viscoelastic properties of single poly(ethylene glycol) molecules.

The viscoelastic properties of single poly(ethylene glycol) (PEG) molecules were measured by analysis of thermally and magnetically driven oscillations of an atomic force microscope (AFM) cantilever/molecule system. The molecular and monomer stiffness and friction of the PEG polymer were derived using a simple harmonic oscillator (SHO) model. Excellent agreement between the values of these two parameters obtained by the two approaches indicates the validity of the SHO model under the experimental regimes and the excellent reproducibility of the techniques. A sharp minimum in the monomeric friction is seen at around 180 pN applied force which we propose is due to a force induced change in the shape of the energy landscape describing the conformational transition of PEG from a helical to a planar state, which in turn affects the timescale of the transition and therefore modifies the measured internal friction. A knowledge of the viscoelastic response of PEG monomers is particularly important since PEG is widely used as a linker molecule for tethering groups of interest to the AFM tip in force spectroscopy experiments, and we show here that care must be exercised because of the force-dependent viscoelastic properties of these linkers.     

Kinetic resolution of vic-amino alcohols catalyzed by a chiral Cu(II) complex

Kinetic resolution of N-benzoylated vic-amino alcohols was achieved by benzoylation in the presence of copper triflate and (R,R)-Ph-BOX as catalysts. The observed enantioselectivity was moderate to high. The method was applied to a kinetic resolution of racemic prolinol and piperidinemethanol derivatives as well as an asymmetric desymmetrization of 2-amino-1,3-diol derivatives.     

Direct Asymmetric Mannich‐Type Reaction of α‐Isocyanoacetates with Ketimines using Cinchona Alkaloid/Copper(II) Catalysts

The enantioselective direct Mannich‐type reaction of ketimines with α‐isocyanoacetates has been developed. Excellent yields and enantioselectivity were observed for the reaction of various ketimines and α‐isocyanoacetates using cinchona alkaloid/Cu(OTf)₂ and a base. Both enantiomers of the products could be obtained by using pseudoenantiomeric chiral catalysts. This process offers an efficient route for the synthesis of α,β‐diamino acids.     

Catalytic Enantioselective Reaction of α‐Phenylthioacetonitriles with Imines Using Chiral Bis(imidazoline)–Palladium Catalysts

The catalytic enantioselective reaction of α‐phenylthioacetonitriles with imines has been developed. The reaction of various imines proceeds in good yields and diastereo‐ and enantioselectivities in the presence of chiral bis(imidazoline)–palladium catalysts. The obtained products can be converted into β‐aminonitrile or β‐aminoamide compounds without loss of enantiopurity.     

Tin-free intermolecular addition of primary alkyls to imines via the dimethylzinc-air radical process

[reaction: see text] A dimethylzinc-air initiator was applied to the generation of primary alkyl radicals from alkyl iodides. The addition of the generated primary alkyl radicals to N-tosylimines was accelerated by the action of boron trifluoride-diethyl etherate and copper(II) triflate to give the corresponding adducts in good yields after 2-3 h. Air oxygen was essential for the reaction to proceed, showing involvement of a radical process in the reaction.