Current Organocatalysis - Volume 3, Issue 1, 2016

Metallosurfactant aggregates have grasped a great attention of researchers worldwide owing to their unique surface activity and catalytic efficiency. They serve themselves as perfect blends of both surface science and metallo-organic chemistry. Metallosurfactant aggregates have a variety of fascinating applications like in drug delivery, membrane mimetics, in various separation methods and most importantly in catalytic cleavage of various toxic esters. Due to the resemblance in the catalytic property of metallosurfactant aggregates with natural enzymes they are broadly employed as metalloenzyme mimics for the hydrolysis of activated carboxylic esters, phosphate esters and amides in general laboratory settings. This review summarizes the design and syntheses of metallosurfactant aggregates and their role as proficient catalysts for the hydrolysis of different esters. Special emphasis is given toward the development of structurally diverse surfactant type ligands and use of variety of metal ions specifically for the hydrolytic cleavage of carboxylate and phosphate esters. Generally, the catalytic strengths of numerous synthesized metallosurfactant aggregates have been quantized by exploring kinetic investigations. Hence, a brief account on the quantitative treatment of rate data with the help of kinetic models has also been presented.

During these last twenty years, the syntheses of water-soluble cyclodextrins modified by phosphino groups or imidazolium groups (as precursors of N-heterocyclic carbenes) have been reported. These ligands based on cyclodextrins allowed performing transition metal catalyzed reactions in water. In this review, the molecular recognition properties, the ability of these ligands to immobilize transition metal complexes in water as well as their implications in aqueous organometallic catalysis are discussed.

From the literature covering, Supramolecular Chemistry is the associated with organic synthetic methodology form a new platform for the chemist. This mini-review highlights the unbreakable joints of water with supramolecular catalysis. The goal o f this tutorial review focus on the continuous increase the root of supramolecular catalysis in synthetic chemistry. Cyclodextrins and modified cyclodextrins are cyclic oligosaccharides having cavities, which is hydrophobic in nature and bind with substrates in selective manner. It also promotes reaction with high selectivity. They promote chemical reactions by supramolecular catalysis involving reversible formation of host-guest complexes by noncovalent bonding.

An efficient, mild, cost effective and eco-friendly synthesis of 2,3- dihydroquinazoline- 4(1H)-ones is described in which isatoic anhydride, primary amines and variety of aldehydes react in the presence of citric acid as a green, bioorganic and inexpensive catalyst via rapid one-pot threecomponent reaction in boiling ethanol.

An efficient and selective oxidation of alcohols to aldehydes in high yield in the absence of a base and co-catalyst using a newly synthesized water-soluble heterobimetallic complex [CuZn(bz)3(bpy)2]BF4 has been developed. No appreciable reduction in aldehyde yield occurred even after five recycles.

The mechanism of reaction between 4-methoxybenzaldehyde 1, malononitrile 2, and dimedone 3 in the presence of agar as a green catalyst in a mixture of water and ethanol media as green solvents has been investigated by means of kinetic studies. The rate constant, order of reaction, activation energy and rate determining step (RDS) have been determined. The reaction’s overall order for the formation of tetrahydrobenzo[b]pyran confirmed to second-order kinetics and the partial orders with respect to the reactants 1, 2 and 3 were one, one and zero, respectively. The results showed that rate of reaction speeds up in solvent with high dielectric constant (water/ethanol, 2:1) and decreases with respect to lower dielectric constant (water/ethanol, 1:1) at all temperatures. The first step of the speculative mechanism was recognized as a RDS (K1) in accordance with the effect of solvent on the reaction rate and this was confirmed based upon the steady-state approximation.

The review deals with the Friedel-Crafts asymmetric alkylation of indole and its derivatives by the Michael acceptors under the catalysis of chiral complexes of Lewis acids and chiral Brønsted acids.

Background: 3-Benzyl/alkylindoles are one of the important classes of compounds having several applications. Microwave assisted organic synthesis (MAOS) has gained momentum recently due to the advantages like short reaction time and higher yields compared to conventional heating method. The aim of this paper is to introduce readers to a new methodology of synthesizing these compounds employing microwave assisted synthesis. Methods: We have done review of literature related to the various indole derivatives having medicinal applications and methods available to synthesize them. We have reviewed various methodologies for the C-3 alkylation of indoles including reductive alkylations developed to obtain 3-arylmethylindoles. We have used microwave irradiation to obtain 3- benzyl/alkylindoles in very good yield. Results: A facile route to 3-benzyl/alkylindoles via deamination of tertiary amine followed by a metal-free catalytic transfer hydrogenation of Mannich bases of indoles under microwave irradiation has been developed. Deamination is catalyzed by p-TsOH and Hantzsch 1,4-dihydropyridine is used as the reductant. The reaction proceeded through an alkylideneindolenine ion. The reaction is simple, clean and offers very good yield of the products. Conclusion: An efficient method is developed for the synthesis of 3-benzylated/alkylated indoles. The reaction does not use any hazardous metal catalyst or reductant. The method uses p-TsOH as catalyst which is a convenient, easily available and cheap reagent. This method would offer easy and economic solution for synthesis of this important class of compounds augmenting the presently available procedures.