2,3-Unsaturated enoses. A Pummerer rearrangement route to sugar vinyl sulfides and synthesis of 3-deoxy-3-alkyl/arylsulfinyl pyranosides

A Pummerer rearrangement of 2,3-dideoxy-3-alkyl/arylsulfinyl-arabino-hexopyranosides is reported. Treatment of sulfinyl-arabino-hexopyranoside derivatives, obtained through oxidation of the corresponding thio-derivatives, with trifluoroacetic anhydride (TFAA)/pyridine led to a facile formation of 2,3-dideoxy-3-alkyl/arylthio-hex-2-enopyranosides. Upon conversion of sugar vinyl sulfides to vinyl sulfoxides, conjugate addition reactions were conducted with alkoxides, to afford 3-deoxy-3-alkyl/arylsulfinyl pyranosides, in the manno-configuration exclusively. Whereas the conjugate addition reaction did not proceed with ether protecting groups, ester protecting groups and free hydroxyl groups in the sugar vinyl sulfoxide permitted the reaction. (C) 2012 Elsevier Ltd. All rights reserved.

Electrocatalytic oxidation of C-3-aliphatic alcohols on electrodeposited Pd-PEDOT nanodendrites in Alkaline medium

Nanodendritic Pd is electrodeposited on poly(3,4-ethylenedioxythiophene) (PEDOT) coated carbon paper electrode. Electrodeposited Pd is non-dendritic in the absence of PEDOT. The electrooxidation of C-3-aliphatic alcohols, namely, propanol (PA), 1,2- propanediol (1, 2-PD), 1, 3-propanediol (1, 3-PD), and glycerol (GL) is studied in 1.0 M NaOH. The catalytic activity of nanodendritic Pd is greater than that of non-dendritic Pd for oxidation of the four alcohols molecules. Among those molecules the oxidation rate increases as: PA< 1, 2-PD < 1, 3-PD < GL. The cyclic voltammetric oxidation current peak appearing in the reverse direction of the sweep is greatly influenced by the nature of alcohol. The reduction of oxide film on Pd surface is attributed to affect the magnitude of backward peak current density. The amperometry and repeated cyclic voltammetry data suggest a high stability of nanodendritic Pd in alkaline medium. Glycerol is expected to be an appropriate alcohol for application as a fuel in alkaline fuel cells at nanodendritic electrodeposited Pd.

Facial selectivities in the nucleophilic additions of 2,3-unsaturated 3-arylsulfinyl pyranosides

2,3-Unsaturated 3-arylsulfinyl pyranosides undergo nucleophilic additions at C-2, with facial selectivities depending on the nucleophile and the substituent on sulfinyl sulfur. The reactions of such sugar vinyl sulfoxides lead to the addition of nucleophile preferring an axial orientation at C-2, with concomitant formation of an allylic bond at C-3 to C-4. This trend in the addition pattern is observed for primary amine, carbon and sulfur nucleophiles, whereas secondary amines prefer an equatorial addition at C-2. The effect of p-tolylthio-versus (p-isopropylphenyl)thio vinyl sulfoxide is that the equatorial nucleophilic addition is preferred even more with the latter vinyl sulfoxide. (C) 2013 Published by Elsevier Ltd.

Synthesis of substituted nitroolefins: a copper catalyzed nitrodecarboxylation of unsaturated carboxylic acids

A novel, mild and convenient method for the nitrodecarboxylation of substituted cinnamic acid derivatives to their nitroolefins is achieved using a catalytic amount of CuCl (10 mol%) and tert-butyl nitrite (2 equiv.) as a nitrating agent in the presence of air. This reaction provides a useful method for the synthesis of beta,beta-disubstituted nitroolefin derivatives, which are generally difficult to access from other conventional methods. Additionally, this reaction is selective as the E-isomer of the acid derivatives furnishes the corresponding E-nitroolefins. One more salient feature of the method is, unlike other methods, no metal nitrates or HNO3 are employed for the transformation.

Cross-Hetero-Dehydrogenative Coupling Reaction of Phosphites: A Catalytic Metal-Free Phosphorylation of Amines and Alcohols

Phosphorylation of amines, alcohols, and sulfoximines are accomplished using molecular iodine as a catalyst and H2O2 as the sole oxidant under mild reaction conditions. This method provides an easy route for synthesizing a variety of phosphoramidates, phosphorus triesters and sulfoximine-derived phosphoramidates which are of biological importance.

In situ approach for testing the enantiopurity of chiral amines and amino alcohols by H-1 NMR

An in situ approach involving a simple mix and shake method for testing the enantiopurity of primary, secondary and tertiary chiral amines and their derivatives, chiral amino alcohols, by H-1-NMR spectroscopy is developed. The protocol involves the in situ formation of chiral ammonium borate salt from a mixture of C-2 symmetric chiral BINOL, trialkoxyborane and chiral amines. The proposed concept was demonstrated convincingly on a large number of chiral and pro-chiral amines and amino alcohols, and also aids the precise measurement of enantiomeric excess. The protocol can be completed in a couple of minutes directly in the NMR sample tube, without the need for any physical separation.

Copper-Catalyzed Oxidative Transformation of Secondary Alcohols to 1,5-Disubstituted Tetrazoles

A mild and convenient oxidative transformation of secondary alcohols to 1,5-disubstituted tetrazoles is uncovered by employing trimethylsilyl azide (TMSN3) as a nitrogen source in the presence of a catalytic amount of copper(II) perchlorate hexahydrate Cu(ClO4)(2)(.)6H(2)O] (5mol%) and 2,3-dichloro-5,6-dicyano-para-benzoquinone (DDQ) (1.2equiv.) as an oxidant. This reaction is performed under ambient conditions and proceeds through CC bond cleavage.

Copper-Catalyzed Decarboxylative Sulfonylation of alpha,beta-Unsaturated Carboxylic Acids

Copper-catalyzed, ligand-promoted decarboxylative coupling of readily available a,fi-unsaturated acids with sodium aryl sulfinates is presented. This method provides a new avenue for the synthesis of vinyl sulfones via a decarboxylative radical coupling strategy by employing a catalytic amount of Cu(ClO4)(2)center dot 6H(2)O, TBHP in decane as an oxidant, and 1,10-phenanthroline as a ligand. The salient feature of this method is that it furnishes exclusively the (E)-isomer.

Role of degree of saturation in denitrification of unsaturated sand specimens

Nitrate contamination of groundwater arises from anthropogenic activities, such as, fertilizer and animal manure applications and infiltration of wastewater/leachates. During migration of wastewater and leachates, the vadose zone (zone residing above the groundwater table), is considered to facilitate microbial denitrification. Particle voids in vadose zone are deficient in dissolved oxygen as the voids are partially filled by water and the remainder by air. Discontinuities in liquid phase would also restrict oxygen diffusion and therefore facilitate denitrification in the vadose/unsaturated soil zone. The degree of saturation of soil specimen (S (r)) quantifies the relative volume of voids filled with air and water. Unsaturated specimens have S (r) values ranging between 0 and 100 %. Earlier studies from naturally occurring nitrate losses in groundwater aquifers in Mulbagal town, Kolar District, Karnataka, showed that the sub-surface soils composed of residually derived sandy soil; hence, natural sand was chosen in the laboratory denitrification experiments. With a view to understand the role of vadose zone in denitrification process, experiments are performed with unsaturated sand specimens (S (r) = 73-90 %) whose pore water was spiked with nitrate and ethanol solutions. Experimental results revealed 73 % S (r) specimen facilitates nitrate reduction to 45 mg/L in relatively short durations of 5.5-7.5 h using the available natural organic matter (0.41 % on mass basis of sand); consequently, ethanol addition did not impact rate of denitrification. However, at higher S (r) values of 81 and 90 %, extraneous ethanol addition (C/N = 0.5-3) was needed to accelerate the denitrification rates.

Synthesis of Azepino4,5-b]indolones by an Intramolecular Cyclization of Unsaturated Tryptamides

A facile general route for the synthesis of azepino4,5-b]indolones is presented. The strategy involves a Bronsted acid assisted intramolecular cyclization of unsaturated tryptamides. The methodology developed has been applied to the synthesis of the ABCD tetracyclic core of the natural product tronocarpine.

Chiral discrimination of secondary alcohols and carboxylic acids by NMR spectroscopy

The manuscript reports two novel ternary ion-pair complexes, which serve as chiral solvating agents, for enantiodiscrimination of secondary alcohols and carboxylic acids. The protocol for discrimination of secondary alcohols is designed by using one equivalent mixture each of enantiopure mandelic acid, 4-dimethylaminopyridine (DMAP) and a chiral alcohol. For discrimination of carboxylic acids, the ternary complex is obtained by one equivalent mixture each of enantiopure chiral alcohol, DMAP and a carboxylic acid. The designed protocols also permit accurate measurement of enantiomeric composition. Copyright (C) 2014 John Wiley & Sons, Ltd.

Analyzing the kinetic response of tin oxide-carbon and tin oxide-CNT composites gas sensors for alcohols detection

Tin oxide nanoparticles are synthesized using solution combustion technique and tin oxide - carbon composite thick films are fabricated with amorphous carbon as well as carbon nanotubes (CNTs). The x-ray diffraction, Raman spectroscopy and porosity measurements show that the as-synthesized nanoparticles are having rutile phase with average crystallite size similar to 7 nm and similar to 95 m(2)/g surface area. The difference between morphologies of the carbon doped and CNT doped SnO2 thick films, are characterized using scanning electron microscopy and transmission electron microscopy. The adsorption-desorption kinetics and transient response curves are analyzed using Langmuir isotherm curve fittings and modeled using power law of semiconductor gas sensors. (C) 2015 Author(s).

Copper-Catalyzed Direct Transformation of Secondary Allylic and Benzylic Alcohols into Azides and Amides: An Efficient Utility of Azide as a Nitrogen Source

A mild and convenient method for the synthesis of amides has been explored by using secondary alcohols, Cu(ClO4)(2)6H(2)O as a catalyst, and trimethylsilyl azide (TMSN3) as a nitrogen source in the presence of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) at ambient temperature. This method has been successfully adapted to the preparation of azides directly from their corresponding alcohols and offers excellent chemoselectivity in the formation of -halo azides and the azidation of allylic alcohols in the presence of a benzyl alcohol moiety. In addition, this strategy provides an opportunity to synthesize azides that can serve as precursors to -amino acids.

Enantio sensing property of helicin, the derivative of a natural product: Discrimination of amines and amino alcohols

The chiral sensing property of helicin (the derivative of natural product obtained by partial oxidation of salicin, extracted from willow tree (Salix helix)) is reported. The use of helicin as a chiral derivatizing agent for the discrimination of amines and amino alcohols is convincingly established using H-1 NMR spectroscopy. The large chemical shift separation achieved between the discriminated peaks facilitated the accurate quantification of enantiomeric composition. The consistent trend observed in the shifting of imine proton peak (Delta delta) of helicin in all the derivatized molecules might aid the determination of spatial configuration. (C) 2015 Elsevier B.V. All rights reserved.

Enantio sensing property of helicin, the derivative of a natural product: Discrimination of amines and amino alcohols

The chiral sensing property of helicin (the derivative of natural product obtained by partial oxidation of salicin, extracted from willow tree (Salix helix)) is reported. The use of helicin as a chiral derivatizing agent for the discrimination of amines and amino alcohols is convincingly established using H-1 NMR spectroscopy. The large chemical shift separation achieved between the discriminated peaks facilitated the accurate quantification of enantiomeric composition. The consistent trend observed in the shifting of imine proton peak (Delta delta) of helicin in all the derivatized molecules might aid the determination of spatial configuration. (C) 2015 Elsevier B.V. All rights reserved.