K. C. Rajanna

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.

AMMONIUM NICKEL SULPHATE MEDIATED NITRATION OF AROMATIC COMPOUNDS WITH NITRIC ACID

Aromatic compounds were efficiently nitrated under mild conditions employing ammonium nickel sulphate and nitric acid as a reagent. This procedure works efficiently at room temperature yielding mononitro derivative in fair to good yield with high regioselectivity.

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.

Mild and Efficient Nitration of Aromatic Compounds Mediated by Transition-Metal Complexes

Abstract Aromatic compounds were efficiently nitrated under facile reaction conditions by employing 69% nitric acid catalyzed by transition-metal complexes such as [Co(NH3)5Cl]Cl2, [Cu(NH3)4]SO4, Mn(acac)3, [Ni(NH3)6]Cl2, [Ni(en)3]S2O3, and Hg[Co(SCN)4]. The reaction was completed smoothly at room temperature and afforded corresponding mono-nitro derivatives in quantitative yield. This new method offers efficient and facile regioselective mononitration of aromatic compounds.

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 formylation of coumarin derivatives. A solvent dependent kinetic study

A kinetic study of the reaction of coumarin derivatives with Vilsmeier-Haack (VH) reagent (1:1 DMF-POCl3) in various solvent media revealed second-order kinetics with a first-order in [Substrate] and first-order in [VH reagent]. The reaction rates altered nonlinearly with an increase in the dielectric constant of the medium and the data did not fit completely well with either Amis or Kirkwoods theories of ion (SINGLEBOND) dipole and dipole (SINGLEBOND) dipole type reactions. On the basis of kinetic and spectroscopic results, participation of VH-adduct and coumarin molecule in the rate limiting step, has been proposed. Kinetic and activation parameters have been evaluated and discussed in terms of isokinetic relationship and as a function of solvent compositions. Linearity of Lefflers and Exners plots indicate a similar type of mechanism to be operative in different dielectric media at all temperatures.

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).