Current Organic Chemistry - Volume 11, Issue 12, 2007

With this second part of the special issue on “Synthetic Organic Chemistry”, inserted in the Volume 11, Number 12, August 2007 of Current Organic Chemistry, I close, as Guest Editor, the first year of activity, including three reviews which deal with the chemistry of sulfenic acids, and furan oxidations, and photooxygenation of non-aromatic heterocycles. The first review, written by M.C. Aversa, A. Barattucci, P. Bonaccorsi and P. Giannetto of the Department of Organic and Biological Chemistry in Messina University, includes 56 references and provides a comprehensive survey of the literature on sulfenic acid chemistry from 1990 through June 2006, focusing the attention on salient aspects of their structures and involvement in organic processes. The stability of some sulfenic acids has allowed the comprehension of their chemical and physical properties and indirectly of the role that Cys-SOHs play in protein biochemistry. However, in many papers of organic chemistry their intermediacy is apparent: once generated, they are involved in intra- and intermolecular additions to unsaturated molecules. Few examples of sulfenic acid addition to double and triple bonds have been recently described and most of them are intramolecular processes. Some applications there are also described where the thermical elimination from sulfinyl precursors is used as a method for removing the sulfinyl moiety from organic molecules and forming double bonds with controlled stereochemistry, in addition to the way to generate sulfenic acids. The second review, provided by M. R. Iesce, F. Cermola, and M.Rubino of the Department of Organic Chemistry and Biochemeistry of Naples University, Federico II, was dedicated to the photo-oxygenation of non-aromatic heterocycles. The review, including 102 references, furthermore, deals with cyclic compounds containing non usual hetero-atoms, namely silicon, germanium and tellurium, and involves all the three types of photo-oxygenation (Types I-III). Moreover, the hetero-atom can be frequently involved endorsing electron-transfer reactions which turn out to be the main pathways, even in singlet oxygen oxygenation. There is a vast collection of photo-oxygenation examples, where novel and unexpected products are formed, some times in a stereochemical manner. P. Merino, T. Tejero, J. I. Delso and R. Matute of the Laboratorio de Sintesis Asimetica in the Departamento de Quimica Organica, Universidad de Zaragoza, and Departamento de Ingenieria Quimica y Tecnologias del Medio Ambiente of the Escuela Universitaria de Ingenieria Industrial in Zaragoza, Aragon (Spain) have contributed to the third work where of oxidation reactions of several furan derivatives as effective methods for the preparation of key synthetic intermediates are reviewed. Recent advances and applications of furan oxidations in organic synthesis are described, where, depending on the oxidizing reagent, the furan ring can be considered as a C-1 or C-4 synthon, leading, upon different conditions, to 1,4- dicarbonyl compounds, carboxylic acids, pyranones or butenolides. I would like to my sincere thanks are expressed to the contributors of this second part of this special issue on “Synthetic Organic Chemistry” for their excellent reviews on their very interesting researches.

This review provides a comprehensive survey of the literature on sulfenic acid chemistry from 1990 through June 2006, focusing the attention on salient aspects of their structures and involvement in organic processes. Even if the majority of known sulfenic acids cannot be isolated, some stable ones have been obtained, and their study helped dramatically the comprehension of chemical and physical properties of all sulfenic acids and indirectly of the role that Cys-SOHs play in protein biochemistry. Many papers have been published in the last fifteen years about the sulfenic acid intermediacy in organic chemistry. Once generated, they can be involved in intra- and intermolecular additions to unsaturated molecules. Few examples of sulfenic acid addition to double bonds have been recently described and most of them are intramolecular processes, whereas the addition of enantiopure sulfenic acids onto carbon-carbon triple bonds has been widely exploited in the synthesis of vinyl sulfoxides to be used in many stereoselective transformations. The thermic β- elimination from sulfinyl precursors is a way to generate sulfenic acids but it has been also used for removing the sulfinyl moiety from organic molecules and forming double bonds with controlled stereochemistry. Some significant applications of extrusion processes are also described in the present review.

Photooxygenation of non-aromatic heterocycles and cyclic compounds containing non-usual heteroatoms, namely silicon, germanium and tellurium has been reviewed. All three types of photooxygenation (Types I-III) can take place. Moreover the heteroatom can be frequently involved endorsing electron-transfer reactions which turn out to be the main pathways, even in singlet oxygen oxygenation. A vast collection of novel and unexpected products are often formed, sometimes in a stereocontrolled manner.

Oxidation reactions of several furan derivatives as effective methods for the preparation of key synthetic intermediates are reviewed. Depending on the oxidizing reagent the furan ring can be considered as a C-1 or C-4 synthon, which upon different conditions leads to 1,4-dicarbonyl compounds, carboxylic acids, pyranones or butenolides.

Tuberculosis (TB) and fungal diseases are opportunistic infections that very often complicate the immunological response in HIV-infected individuals [1-3]. During our studies on novel antimycobacterial and antifungal agents we synthesized a number of new pyrrole derivatives and among them some proved very active against both fungi and mycobacteria. Some others instead were very selective against mycobacteria only. So we pursued a program aimed at individuating the chemical groups or their association, responsible for the particular activity. Moreover, many other pyrroles we synthesized showed to be very active as COX-2 selective inhibitors. In this review we describe our approaches to the synthesis of the pyrrolic structures studied.