Editorial [Hot Topic: Synthetic Organic Chemistry (Guest Editor: Antonino Corsaro)]

The first part of a special issue on “Synthetic Organic Chemistry”, with which I have initiated my activity of Guest Editor, is inserted in this Volume 11, Number 11, July 2007 of Current Organic Chemistry. It has indeed been a great pleasure to be associated with this venture that allows to introduce me to the various colleagues for the first time. Certainly, since I have got an engagement for the next two years, this my new activity will be improved in the future; in particular, it will aim at shortening publication times of reviews.

In this publication four reviews are reported that brings the readers to the field of heterocycles syntheses and utilization of carbon dioxide in the synthesis of organic carbammates

The first thick review, written by Paolo Quadrelli and Pierluigi Caramella from the University of Pavia (Italy) is comprehensive of the synthesis and synthetic applications of the 1,2,4-oxadiazole-4-oxides which have never been made before.

In the initial part of the review, including 52 references, the aim of Authors is to account the state of the art in the synthesis of 1,2,4-oxadiazole-4-oxides, starting from the very first approaches up to the most recent methods, which is discussed in details. They highlight as 1,2,4-Oxadiazole-4-oxides are a family of heterocycles closely related to the chemistry of nitrile oxides which were actively studied in the past half century and provided the basic knowledge on 1,2,4-oxadiazole-4-oxides.

The final part of the review, including 35 references, will be dedicated to the chemical behaviour of 1,2,4-oxadiazole-4- oxides, mainly concerning their chemical stability and their use as precursors of reactive species, even coupled with new synthetic methodologies. Their chemistry is related to the fragility of their heterocyclic ring, which undergoes thermal or photochemical cycloreversion to nitriles and nitrosocarbonyl intermediates. Trapping of nitrosocarbonyls takes place easily with dienes and enes, affording a variety of hetero Diels-Alder and ene adducts, which attract great interest because of their useful synthetic elaboration toward many natural products of potential pharmaceutical applications. The photochemical cleavage have been applied successfully to solid phase chemistry, allowing for a safe and environmental friendly methodology for the synthesis of important intermediates.

Devdutt Chaturvedi and Suprabhat Ray from Medicinal and Process Chemistry Division of Indian Central Drug Research Institute contributed to the second review, which deals with the synthesis of organic carbamates extensively based on the utilization of carbon dioxide as a cheap and harmless reagent in alternative to harmful and toxic, but classically used, reagents like phosgene, and its derivatives or carbon monoxide.

The review summarizes the preparations of organic carbamates starting from carbon dioxide in the gaseous state affording low yields, but, however, it reportes that yields can be enhanced by using basic catalysts. Good yields of carbamates can be obtained also by supercritical carbon dioxide in the presence of basic and phase transfer systems which act as catalysts. Alternatively, good yields can be achieved also by means of electrochemical processes where the base is electrochemically generated from pyrrolidone, associated with tetraethylammonium cation in the presence of amines, followed by the addition of carbon dioxide and ethyl iodide. The review, including 73 references, comes to an end discussing a comparison of carbamate synthetic methods through the employment of organic carbonates and that one of carbon dioxide.........