Current Organic Chemistry - Volume 14, Issue 8, 2010

Certain cycloalkane-anellated heterocycles undergo rearrangement under basic or acidic conditions via ring-contraction, ringexpansion or ring-opening pathways to afford new or unusual compounds. The reactivities and properties of cycloalkane-fused heterocycles differ significantly from those of heteroaromatic ring systems. Possible mechanisms are also discussed.

Aryl amines and ethers are very important structural motifs of numerous biologically active natural products, important pharmaceutical compounds, polymers in the material science industries and widely used as drugs, dyes, and other fine chemicals. Several studies have earlier been attempted but transition metal mediated protocols have proven more successful results. Conventional Ullmann condensation with copper in the form of metal, alloy or Cu(I)/Cu(II) salt showed major drawbacks such as requirement of high temperature sensitivity to catalyst-type and low to moderate yield. In recent years, copper promoted conventional Ullmann condensation reactions have been improved a lot under ligand and ligand free conditions with excellent conversion. An important Ullmann type coupling, where aryl boronic acids are used as arylating agents instead of aryl halides has recently attracted much attention of chemist. Because of the importance of aryl amines and ethers in various fields of chemistry writing a review in this relevant area is of significant interest. This article will review the applications of copper-promoted C-N and C-O bond formation reactions focused on achievements during the periods from 2000-2008.

The utility of hydrazonoyl halides as precursors in synthesis of numerous biologically active compounds is presented. The biologically active compounds, that have been covered, include lipogenase, lipoxygenase and cyclo-oxygenase inhibitors, antiinflammatories, phytotoxic agents, herbicides, acaricides and miticides, insecticides, weed controlling agents, antimicrobial agents, central benzodiazepine receptors, antitumors, antagonistic agents, analgesics and anticonvulsant agents.

Satins are the most frequently prescribed and efficient drugs for treatment of lipid disorders. These drugs represent one of the most valuable therapeutic classes of compounds in the pharmaceutical sector. Since their discovery as fungal metabolites, many structural modifications have been performed during the past 30 years to obtain structurally refined and even more potent derivatives. These modifications led to the group of fully synthetic statins which are frequently addressed as super-statins. Structurally these compounds consist of a heterocyclic core attached to the chiral 3,5-dihydroxy-6-heptenoic or heptanoic acid side chain. Given their economical importance and well-established therapeutic applications with new indications continuously rising, much effort has been devoted to the improvement of primary synthetic strategies towards super-statins. Indeed, high consumption and multi-ton world wide production of super-statins pose continuous challenge for their economical and eco-friendly synthesis which makes super-statins attractive synthetic target for the organic chemist. Therefore, over the past two decades synthetic chemists have developed an assortment of routes to super-statins. In pursuit to develop easy and practical approaches to super-statins array of new and innovative strategies have been developed. Many of these are outstanding synthetic achievements, especially in the area of chiral side chain synthesis. This review highlights the main methods for the synthesis of super-statin chiral side chain and heterocyclic core building blocks and provides a comprehensive survey of the evolution of synthetic approaches to marketed super-statins: fluvastatin, atorvastatin, rosuvastatin and pitavastatin.

Heterocyclic compounds are versatile building blocks in organic synthesis. These are important part in various natural products and bioactive compounds. Several methodologies have been developed to synthesize these heterocyclic compounds. This review article covers an updated (published during 2005 to 2008) summary of transition-metal catalyzed approaches for the syntheses of commonring heterocycles containing more than one heteroatom via the selective formation of carbon-heteroatom bonds. The five-membered ring heterocycles with two nitrogen atoms include imidazoles, pyrazoles, indazoles, imidazoindolones etc. and heterocycles with one nitrogen and one oxygen atoms include oxazoles, isoxazolines, isoxazolidines etc. Other five-membered heterocycles with one nitrogen and one sulfur atoms as well as one oxygen and one phosphorus/sulfur/silicon atoms have also been included here. Six-membered heterocycles containing two nitrogen atoms such as pyrimidines, pyrazines, phenazines, quinoxazolines etc. have been incorporated. Other six-membered heterocycles containing one nitrogen and one oxygen/sulfur atoms as well as one oxygen and one phosphorus atoms have also been included. Some heterocycles containing three or more heteroatoms have been discussed.