Current Organic Synthesis - Volume 12, Issue 3, 2015

Fused heterocycles constitute the largest diversity of heterocyclic compounds of chemical and biomedical significance. They widely exist in numerous natural products. They are also among the most frequently encountered scaffolds in numerous drugs and pharmaceutically relevant substances. This review highlights some remarkable achievements made in the synthesis and chemistry of pyridotriazolopyrimidines that have appeared in more than the last three decades. The latter heterocyclic ring systems have more than twenty five structures. Moreover, the biological importance of such ring systems is discussed.

Other than their valuable use as starting materials and intermediates in the synthesis of drugs and other important organic compounds, pyridinyl alcohols are largely used as hemilabile chiral chelating ligands in the development of homogeneous transition metal catalysts. The pyridinyl alcohols covered in this review are divided into four types based on the position of the alcohol group and number of the pyridine ring, namely α-pyridinyl alcohols, α,α- pyridinyl diols, α-bipyridinyl alcohols and α,α-bipyridinyl diols. Many synthetic procedures have been conducted by a number of research groups in order to obtain the best synthetic method for these alcohols in the past decades. Significant and remarkable efforts, by many chemists, have been made to synthesise enantiomerically pure pyridinyl alcohols in very good to excellent chemical and optical yields. In this article, a critical overview of the synthetic strategies of the aforementioned pyridinyl alcohols with detailed procedures is provided with the aim of giving a wide scope for the reader in this area.

Polysaccharide is a kind of biological material, which has good biocompatibility, non-toxicity, and nonimmunogenicity. So, the polysaccharide has been widely applied in drug delivery system. The chemical modifications of chitosan and hyaluronic acid as drug carriers were summarized herein.

The conversion of alcohol to alkyl halide in the presence of triphenylphosphine and carbon tetrahalide, which is commonly known as the Appel reaction, is an important route for halogenations under mild and neutral conditions. During the past twenty years, the Appel reaction has experienced a considerable evolution. Several convenient reagents have been developed and applied as electrophilic halogen sources despite a decline in the use of carbon tetrahalides. In addition, modified Appel-type reactions allow for the synthesis of alkyl halides as well as thiocyanates, nitrates, nitrites, amides, esters and acyl halides. Different synthetic methodologies to reduce the byproduct waste from the Appel reaction have been reported in the literature and are presented in this paper. Herein, this review will present recent achievements in the use of novel reagents and synthetic procedures for Appel-type reactions

This review focuses on the recent applications of Burgess reagent in the synthesis of organic compounds, with the emphasis, on the total synthesis of natural occurring products.

A series of new biscoumarins have been synthesized in excellent yields and short reaction times by nucleophilic addition reaction of aldehydes and two equivalents of 4-hydroxycoumarin. The reaction was efficiently promoted by 0.05 g nano Fe3O4 and the catalyst could be recovered easily after the reactions and reused without evident loss of reactivity. All the compounds exhibited strong antibacterial activity towards two Gram positive bacteria, staphylococcus aureus and micrococcus luteus.

Application of silica nanopowder (15 nm) supported by potassium hydrogen sulphate has been demonstrated to be an effective recyclable catalyst system for the opening of terminal epoxide ring using alcohol and/or amine nucleophiles regioselectively at the terminal position in 3 hours at external temperature 70 °C. The terminal insertion of nucleophile has also been observed with potassium bisulphate supported on silica fume surface having particle size 100-150 nm with moderate products yield. Under this mild condition, no extra solvent is required

A new 6-spiro (testosterone-3′-yl)-hexahydro-3-thioxo-1,2,3-triazin-5-ones (4a and 4b) have been synthesized by the condensation of testosterone and17-methyltestosterone(1a and 1b respectively) with thiosemicabazide. The first analogous 5 were obtained by oxidation while the second analogous 6-spiro (testosterone-3′-yl)-3-(4′-fluorophenyl)amino-1,2,3-triazin-5-ones (6) obtained by reaction of 4 with 4-fluoroaniline. These new compounds shows good to moderate affects on the activity of cellobiase produced by Aspergillus nidulans fungi.