Current Organic Chemistry - Volume 16, Issue 4, 2012

Passerini reaction involving an oxo component, an isocyanide, and a nucleophile in a single step to prepare α-acyloxy carboxamide, was first discovered by Passerini about 90 years ago. Various modifications of this reaction have already been developed such as Lewis acids catalysis, in situ oxidation of alcohols to aldehydes, in situ oxidation of aldehydes to carboxylic acids, direct alkylative Passerini reaction, etc. The Passerini reaction has developed in organic synthesis, the total synthesis of natural products, synthesis of polycyclics, macrocycles, heterocycles and pharmaceutical industry for the synthesis of drug-like compounds. The Passerini products could be later cyclized by another type of ring-closing reaction. The aim of this review is to provide an overview of synthetic applications of Passerini reaction.

The number of synthetic applications of epoxide hydrolases in organic chemistry has reached a remarkable level. This has been due to a tremendous amount of work dedicated to the discovery of novel epoxide hydrolases from various biological sources, understanding the structure and function of these widespread enzymes and last but not least, the stabilization of these biocatalysts by various means for production purposes.

Supramolecular chirality has an exciting potential in mimetic enzyme, asymmetric catalyst, separation and analysis of enantiomers, explanation of chiral origin, information recording and reading, functional nanomaterials, and so on. With calixarenes as building blocks, supramolecular chirality with various topologies such as propeller type, single helix, double helices, triple helices and quintuple helices, helical nanotubes, β-sheets, chiral cavity and capsule, (10,3)-a net topology, chiral Kagome lattice, chiral metal nanomaterials, as well as many other asymmetric aggregates existing in solution, solid state and even on two dimensional surface can be realized. This review describes the research works about supramolecular chirality based on calixarenes.

The Biginelli Reaction is a one-pot acid catalysed cyclocondensation of β-keto ester, urea and aromatic aldehyde which leads to the synthesis of functionalised 3,4-dihydro-2(H)-pyrimidinones (DHPMs). This three-component reaction for the synthesis of dihydropyrimidinone and corresponding dihydropyrimidinethiones has now been known for more than a century since first reported in 1893. Owing to the increasing use of Green technology approach, due to its various merits over Classical methodology and as a need for sustainable Chemistry, this reaction has received renewed interest for preparing DHPMs in an environmentally thoughtful manner with improved yields. The classical reaction has been modified in the recent past by using various catalysts and several structural variants in different solvents to synthesize large number of Biginelli type compounds. Also, these DHPMs (synthetic and natural) possess a wide range of pharmacological activities. We hereby wish to compile, in this present review, the literature available methods related to large number of Biginelli type compounds synthesized using eco-friendly technologies. This protocol couples the benefits of Biginelli reaction with that of greener approach for organic transformations, thus facilitating efficient synthesis of bioactive compounds in environmentally benign way.

The catalytic enantioselective aza-Michael reaction is an important transformation in organic chemistry, which has been used for the synthesis of a significant amount of nitrogen-containing products for many research areas in chemistry. In this review, we summarize the literature dealing with catalytic enantioselective versions of this transformation, where a small chiral organic molecule which does not contain metal atoms within its structure (the organocatalyst) is employed for promoting the reaction and also for controlling its stereochemical outcome. Several examples highlighting the successful application of this methodology will also be presented, emphasized by the description of the enantioselective total synthesis of several natural products and therapeutics.

The microwave-assisted double Kabachnik–Fields (phospha-Mannich) reaction of cyclohexylamine, two equivalents of paraformaldehyde and >P(O)H species, such as dialkyl phosphites, ethyl phenyl-H-phosphinate and diphenylphosphine oxide affords the title compounds in good yields. The bis(diphenylphosphinoxido) derivative was converted to the corresponding bidentate chelate platinum complex in two steps, whose stereostructure was elucidated by quantum chemical calculations. The crystal structure of the bidentate chelate complex was studied by X-ray analysis.