P. K. Saiprakash

Cadmium Chloride as an Efficient Catalyst for Neat Synthesis of 5-Substituted 1H-Tetrazoles

Abstract Cadmium chloride (CdCl2) has been found to be an efficient catalyst for a neat [2 + 3]-cycloaddition of NaN3 with nitriles to afford 5-substituted 1H-tetrazoles in good yields. The shorter reaction times, greater yields of the product, and easy workup are the advantages of this methodology.

ULTRASONICALLY ACCELERATED VILSMEIER HAACK CYCLISATION AND FORMYLATION REACTIONS

ABSTRACT Ultrasonically irradiated Vilsmeier Haack (VH) reaction with acetanilides, hydrocarbons and acetophenones exhibited dramatic rate enhancements with excellent yields. The VH reaction with acetanilides afforded 2-chloro-3-formyl quinoline derivatives, hydrocarbons underwent formylation while hydroxy acetophenones yielded 3-formyl chromones.

Antimony Trioxide as an Efficient Lewis Acid Catalyst for the Synthesis of 5-Substituted 1H-Tetrazoles

Abstract Sb2O3 was found to be effective as a catalyst for a smooth (2 + 3) cycloaddition of sodium azide with nitriles to afford 5-substituted 1H-tetrazoles in good yields.

Efficient and Facile Method for the Nitration of Aromatic Compounds by Nitric Acid in Micellar Media

Abstract Aromatic compounds were efficiently nitrated under mild reaction conditions by employing HNO3 in the presence of anionic (sodium dodecyl sulfate, SDS), cationic (cetyl trimethyl ammonium bromide, CTAB), and nonionic (Triton-X 100) micelles. The reaction rapidly afforded corresponding mononitro derivatives in fair to good yields with high regioselectivity. This new method offers an environmentally safe reaction condition to minimize the waste products.

Vilsmeier–Haack Bromination of Aromatic Compounds with KBr and N-Bromosuccinimide Under Solvent-Free Conditions

Abstract Bromination of aromatic hydrocarbons is triggered by Vilsmeier–Haack reagent [N,N-dimethyl formamide (DMF–POCl3 system)] in the presence of KBr or N-bromosuccinimide (NBS) under solvent-free conditions by grinding the reactants in a mortar with a pestle. The reactions afforded corresponding bromo derivatives in very good yield with high regioselectivity. The results are comparable with those obtained under reflux conditions.

Micellar Mediated Halodecarboxylation of α,β‐Unsaturated Aliphatic and Aromatic Carboxylic Acids—A Novel Green Hunsdiecker–Borodin Reaction

A Novel Hunsdiecker‐Borodin reaction (HBR) has been carried out efficiently with α,β‐unsaturated aliphatic and aromatic carboxylic acids by using N‐halo succinimides such as N‐chloro succinimide (NCS), N‐bromo succinimide (NBS), and N‐iodo succinimide (NIS) under micellar media. The reaction with α,β‐unsaturated aromatic carboxylic acids afforded β‐halo styrenes in excellent yield while α,β‐unsaturated aliphatic carboxylic acids underwent decarboxylation and to give corresponding halo derivatives. The reactions are dramatically accelerated in micellar media. This procedure works efficiently in CTAB (cetyl trimethyl ammonium bromide), SDS (sodium dodecyl sulfate), and TX (Triton‐X‐100) media under stirred conditions at room temperature. At reflux temperatures the yield of reaction products were further enhanced from good to excellent.

Vilsmeier Haack Acetylation in Micellar Media: An Efficient One Pot Synthesis of 2‐Chloro‐3‐acetyl Quinolines

Abstract Vilsmeier Haack (VH) acetylations of aromatic hydrocarbons have been carried out by using an N,N‐dimethyl acetamide (DMA)‐POCl3 system to afford the corresponding acetophenones in good yield with high regioselectivity. These acetylations are dramatically accelerated in micellar media. Further it is of interest to note that cyclizations in micellar media under VH conditions are obtained to afford 2‐chloro‐3‐acetyl quinoline derivatives in good yield. This procedure works efficiently in CTAB (cetyltrimethyl ammonium bromide), SDS (sodium dodecyl sulphate), and TX (Triton‐X100) media under reflux conditions (particularly for deactivated acetanilides).

KINETICS AND MECHANISM OF VILSMEIER-HAACK SYNTHESIS OF 3-FORMYL CHROMONES DERIVED FROM O-HYDROXY ARYL ALKYL KETONES : A STRUCTURE REACTIVITY STUDY

Abstract Kinetics of Vilsmeier-Haack reaction with o -hydroxy acetophenones (OHAP) have been investigated in different solvent systems comprising either a single component viz., dichloromethane (DCM), dichloroethane (DCE), acetonitrile (ACN), benzene or binary solvent mixtures of benzene and acetonitrile. The study revealed a total second order kinetics with a first order dependence on each of the [reactant] namely, [VH adduct] and [OHAP]. Increase in the dielectric constant (D) of the medium altered the rate of the reaction non linearly. The data did not fit into either Amis or Kirkwoods theories. These results were interpreted in terms of solvent-solute and solvent-cosolvent interactions. Structure-reactivity correlations have been explained by Hammetts equation.

Hydrogenation of 1-alkenes catalysed by anchored montmorillonite palladium(II) complexes: a kinetic study

Hydrogenation of 1-hexene, 1-heptene and 1-octene was carried out using anchored montmorillonitebipyridinepalladium(II) acetate (CI), montmorillonitebipyridinepalladium(II) chloride (CII) and montmorillonitediphenylphosphinopalladium(II) chloride (CIII) in THF. Under the reaction conditions 100% saturation of the carbon–carbon double bond was observed. The observed rates were first order with respect to the partial pressure of hydrogen and fractional order with respect to [substrate] and [catalyst]. The hydrogenation rates were found to be: 1-hexene > 1-heptene > 1-octene for all three catalysts. The reactivity order of various catalysts is: CI > CII > CIII. Thermodynamic and activation parameters were evaluated. A rate law and a plausible mechanism has been proposed.

A kinetic study of the 1, 10-phenanthroline-catalysed iron(III) oxidation of epimeric aldo-, and D-, and L-ketohexoses

SummaryFeIII in H2SO4 medium does not oxidize sugars even at the reflux temperature, however, the reaction is catalysed by trace amounts of 1,10-phenanthroline (phen). A kinetic study shows that the oxidation rate increases as [phen] increases and exhibits a fractional order dependence upon [phen]. The orders with respect to [FeIII] and [carbohydrate] are unity. The oxidation rate decreases as [HSO4/−] and [H2SO4] increase. A plausible mechanism is proposed involving participation of an [FeIII-phen] precursor and sugar in the rate-determining step.