Catalysis is a topic of continuous interest since it was discovered in chemistry centuries ago. Aiming at the advance of reactions for efficient processes, a number of approaches have been developed over the last 180 years, and more recently, porphyrins occupy an important role in this field. Porphyrins and metalloporphyrins are fascinating compounds which are involved in a number of synthetic transformations of great interest for industry and academy. The aim of this review is to cover the most recent progress in reactions catalysed by porphyrins in scalable procedures, thus presenting the state of the art in reactions of epoxidation, sulfoxidation, oxidation of alcohols to carbonyl compounds and C-H functionalization. In addition, the use of porphyrins as photocatalysts in continuous flow processes is covered.
Sulfonyl
fluorides are valuable synthetic motifs for a variety
of applications, among which sulfur(VI) fluoride exchange-based “click
chemistry” is currently the most prominent. Consequently, the
development of novel and efficient synthetic methods to access these
functional groups is of great interest. Herein, we report a mild and
environmentally benign electrochemical approach to prepare sulfonyl
fluorides using thiols or disulfides, as widely available starting
materials, in combination with KF, as an inexpensive, abundant and
safe fluoride source. No additional oxidants nor additional catalysts
are required and, due to mild reaction conditions, the reaction displays
a broad substrate scope, including a variety of alkyl, benzyl, aryl
and heteroaryl thiols or disulfides.
Tetrabenzoporphyrins have attracted considerable worldwide attention over the last few decades. Since the discovery of these pigments, chemists, biologists, medical professionals and material scientists have devoted pronounced efforts in order to develop synthetic methods and discover useful applications for these compounds. Nowadays, tetrabenzoporphyrins occupy a prominent position in porphyrin chemistry, and this review is intended to cover the main synthetic methods and applications of these compounds.
Endodontic biofilms eradication from the infected root canal system remains as the primary focus in endodontic field. In this study, it was assessed the efficacy of antimicrobial Photodynamic Therapy (aPDT) with the Zn(II)chlorin e6 methyl ester (Zn(II)e6Me) activated by red light against monospecies and mixed biofilms of Enterococcus faecalis and Candida albicans. The results were compared with the ones obtained with Rose Bengal (RB), Toluidine Blue-O (TBO), the synthetic tetracationic porphyrin (TMPyP) as well as classical endodontic irrigants (3% NaOCl, 17% EDTA and 2% CHX). The antimicrobial efficacy of aPDT toward monospecies and mixed biofilms was quantified resorting to safranin red method. The changes of biofilm organization and of cellular ultrastructure were evaluated through several microscopy techniques (light, laser confocal and transmission electron microscopy). Zn(II)e6Me once activated with light for 60 or 90 s was able to remove around 60% of the biofilm’s biomass. It was more efficient than TBO and RB and showed similar efficiency to TMPyP and classical irrigants, CHX and EDTA. As desirable in a PS, Zn(II)e6Me in the dark showed smaller activity than TMPyP. Only NaOCl revealed higher efficiency, with 70–90% of the biofilm’s biomass removal. The organization of biofilms and the normal microbial cell ultrastructure were extensively damaged by the presence of Zn(II)e6Me. aPDT with Zn(II)e6Me showed to be an efficient antimicrobial strategy deserving further studies leading to a future clinical usage in endodontic disinfection.
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