V. Gouverneur, K. Seppelt
Jan 28, 2015
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Influential Citations
146
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Chemical reviews
Abstract
Past advances in research and modern chemistry have advanced understanding of how the distinctive place of fluorine in the periodic table impacts on the structure, reactivity, and function of fluorine-containing molecules. As a result, a large variety of materials, polymers, catalysts, and agrochemical or pharmaceutical drugs contain variously sized and shaped fluorine substituents. The field goes far beyond these advances, since fluorine has played an important role to access fluorine-free molecules and extravagantly per-fluorinated compounds displaying unusual properties. In this thematic issue ofChemical Reviews, several areas are explored, but by no means is the collection of selected papers comprehensive of the recent advances made in the field. To have a fuller appreciation of the impact of fluorine, the readers are invited to get familiar with the properties and use of per-fluorinated organic compounds and fluorinated polymers, the occurrence of man-made fluorinated entities found in the atmosphere, as well as the impact of fluorine substitution in agrochemistry and drug discovery. Much is also known of the effect of fluorine on intermolecular behavior (surfactants) or the chemistry of B, P, S, or halogen fluorides, to name only a few additional facets not covered here. However, researchers new to the field, as well as others actively engaged, will find broad insights on fluorine chemistry with papers selected herein and written by leaders in the field. This issue presents a long awaited review showcasing the utility of tetrafluoroborates and boron trifluoride as nucleophilic fluoride sources. Nucleophilic fluorination complements electrophilic and radical fluorination processes, so the account of S. Davies and co-workers is timely. The iconic Balz−Schiemann reaction leading to aryl fluorides via thermal decomposition of aryldiazonium tetrafluoroborate salts is described first followed by a range of nucleophilic substitution leading to alkenyl fluorides, alkyl fluorides, gem-difluorides, glycosyl fluorides, and α-fluoro carbonyl compounds. Next, the ring-opening fluorinations of strained rings are described followed by addition reactions to alkenes, alkynes, and allenes, and Prins-type cation-π cyclization-fluorinations. T. Ritter and co-workers review next all the “modern carbon− fluorine bond forming reactions” leading to aryl fluorides. The fluorination of arenes is an important area of research, as the fluorine substitution can have drastic effects on their properties and, in the case of drug molecules, can influence how well they are absorbed into the body and how resistant they are to metabolism. This authoritative account updates readers with the most recent approaches toward late stage fluorination of arenes from a range of precursors. D. O’Hagan discusses in full the discovery, structure, and activity of fluorinase enzyme, a remarkable enzyme capable of catalyzing a nucleophilic fluorination process. The emphasis is on enzymatic C−F bond formation followed by a comprehensive account on how the discovery of this unique enzyme has led to various biotechnological developments, including fluorometabolite engineering, the incorporation of fluoroacetyl-CoA and fluoromalonyl-CoA into polyketide frameworks, and the use of fluorinase to access F-labeled molecules for applications in positron emission tomography. This latter application culminates with a method allowing for the direct F-labeling of peptides with cyclotron-produced F-fluoride. From the review of A. Togni and co-workers, the readers will gain insight on two hypervalent iodine compounds developed in the authors’ laboratory for electrophilic trifluoromethylation; these compounds, namely 1-(trifluoromethyl)-1,2-benziodoxol3(1H)-one and trifluoromethyl-1,3-dihydro-3,3-dimethyl-1,2benziodoxole, are now commercially available reagents, that have contributed enormously to invigorate the field of late stage trifluoromethylation. This critical review describes how these reagents are best prepared, activated, and applied for both heteroatom−CF3 and C−CF3 bond construction. Mechanistic consideration enhances this account, distinguishing between Lewis acids, metal, and radicals as activation manifold to induce trifluoromethylation. Complementing Togni’s review on electrophilic trifluoromethylation, X. Liu, C. Xu, M. Wang, and Q. Liu present a piece on trifluoromethyl-triethylsilane and its use in nucleophilic trifluoromethylation mediated or not by transition metals. This is a vast account providing a comprehensive grasp of the impact that this so-called Ruppert−Prakash reagent has made on fluorine synthetic chemistry. The additional section on the most recent developments, that appeared after the paper was submitted, is a clear indicator that this reagent will continue to be abundantly used for the construction of CF3and CF2containing molecules. Synthetic methods for compounds having SCF3 units on carbon, such as trifluoromethylation, trifluoromethylthiolation, and triflylation, are provided in the manuscript written by N. Shibata and his co-workers. The key characteristics of CF3, OCF3, SCF3, SOCF3, and SO2CF3 are outlined in the introduction followed by an impressive review presenting the various chemistries available to date to install these SCF3 motifs into simple and more functionalized targets. The authors highlight that further developments are necessary, especially toward methods based on C−H functionalization or asymmetric variants for control over stereogenicity. C. Ni and M. Hu follow with a manuscript focusing on the sulfur-based fluorination and fluoroalkylation reagents for organic synthesis. As expected, sulfur tetrafluoride derivatives, sulfonyl fluorides, and sulfonium fluorides appear early in this review followed by sulfur-based perfluoroalkylation reagents for perfluoroalkylation themselves, difluoromethylation, difluoroolefination, and monofluoromethylation. This is another timely account displaying how sulfur and fluorine can be used in synergy to control reactivity. The review of F. D. Toste and co-workers distinguishes itself by discussing the issue of F-stereogenicity using both metalinduced and organocatalytic processes. Advances in catalytic enantioselective fluorination show that the field is dominated by electrophilic fluorination with only a few transformations using