Organophosphorus Chemistry: Volume 49
Published:14 Apr 2020
David Allen, David Loakes, Lee Higham, John Tebby, 2020. "Preface", Organophosphorus Chemistry: Volume 49, David W Allen, David Loakes, Lee J Higham, John C Tebby
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This volume, No. 49 in the series, (first published in 1970 under the editorship of Professor Stuart Trippett), covers the literature of organophosphorus chemistry published in the period from January 2018 to January 2019, and continues our efforts to provide an up-to-date survey of progress in this topic, which continues to generate a vast amount of research. We continue to be fortunate in securing contributions from a team of international authors from Germany, Poland, Portugal, Italy, Russia, Hungary and India. This year, we welcome to our team of Editors, Dr Lee Higham, of the School of Natural and Environmental Sciences in the University of Newcastle, who will take over the direction and planning of this series from volume 50. The continuing vitality of research in phosphorus chemistry was demonstrated at the 22nd International Conference on Phosphorus Chemistry, held in Budapest in July 2018. Papers from this conference have been published in Phosphorus, Sulfur, Silicon and Related Elements, 2019, volume 194, pp. 269–613.
The annual survey of the literature relating to the chemistry of traditional phosphines containing only P–C and P–H bonds again includes the synthesis of new phosphines, classified according to the synthetic approaches used, data concerning the reactivity of phosphines, (mainly the attack of phosphorus at carbon or other atoms, excluding metal complexation, and the formation of P(v) derivatives of phosphines) and the application of phosphines in organocatalysis and other fields of chemistry or adjacent sciences.
The chapter relating to tervalent phosphorus acid derivatives includes synthetic methodologies to halogenophosphorus compounds, phosphorus amides (aminophosphines, phosphoramidites and diamidophosphites), phosphorus esters (phosphinites, phosphonites and phosphites) and mixed phosphorus compounds bearing two different tervalent phosphorus moieties. A critical selection of their applications is briefly assessed, with an emphasis on the catalytic applications of ligands and their metal complexes.
In phosphine chalcogenide chemistry, the development of methods for their synthesis, and their applications as new components in opto-electronic devices, has again shown considerable growth. Their additions to unsaturated substrates and P–C coupling reactions, continue to present a very active area.
The chemistry of phosphonium salts and related ylides also continues to show remarkable vitality, with particular reference to catalytic applications and, in particular, to the synthesis and applications of phosphonium salts as ionic liquids that display higher thermal and electrochemical stabilities compared to related ammonium salts and which also have potential as new solvents in organic synthesis and as stabilisers for nanoparticle systems.
In this volume, we regret that we are unable to provide a report of progress in the chemistry of nucleic acids and mononucleotides. Nor has it been possible to find authors willing to cover progress in the related areas of oligo-, and poly-nucleotides. However, the quinquevalent organophosphorus acids area continues to grow in importance and activity. This chapter again reports progress in the chemistry of compounds possessing, in addition to the phosphoryl group PO, three P–O bonds (phosphates), two P–O bonds and one P–C bond (phosphonates) and one P–O and two P–C bonds (phosphinates), and is structured to cover synthesis, reactions and biological aspects. Each section covers a variety of topics, such as new reagents, new methods of synthesis, total and stereocontrolled syntheses, multicomponent reactions as well as biological investigations. The area of phosphoric acids and their derivatives has again shown particular growth during this review period. The interest in phosphoric, phosphinic and phosphonic acids as catalysts grows constantly year-on-year, and chiral phosphorus(v) acids have been used in a vast array of chemical reactions.
Work on five- and six-coordinate phosphorus compounds and their derivatives remains a significant area of interest, although the chemistry of five-coordinate systems continues to dominate. This year's review is divided into the above main subsections i.e. five coordinate- and six coordinate-compounds. The former includes studies of synthesis, structure and reactivity as well as their involvement as intermediates and transition states. In this respect, a synthetic strategy for novel metallophosphoranes, together with the chemistry of selected spirophosphoranes and fluorinated phosphoranes, have been described. Moreover, fragmentation pathways of aryloxyspirophosphoranes have also been proposed. The involvement of pentacoordinated intermediates or transition states in phosphine-mediated phosphodiester cleavage reactions have been reviewed. The importance of pentacoordinated species as key intermediates in the oligomerization of isocyanates, monosaccharides and the polymerisation of cyclic ethylene phosphate, has been confirmed. With respect to hexacoordinated compounds, there has been limited attention paid to the synthesis and application of novel anions. However, a report on the preparation of a neutral hexacoordinate phosphorus-ruthenium complex has appeared.
The phosphazene chapter covers acyclic phosphazenes, cyclophosphazenes and polyphosphazenes. Among the many examples presented, notable personal highlights with potential biological applications include the utilisation of the PN bond for bioconjugation via the Staudinger reaction of an activated 2,6-dichlorophenylazide motif, to allow for chemical modification of proteins in live cells, whilst tris(o-phenylenedioxy)cyclotriphosphazene has shown an ability to trap radicals such as phenylnitrosylnitroxide, which may be exploited to provide clarification of chemical or biological structures of nanomaterials, whilst nanovesicles based on amphiphilic polyphosphazenes have been shown to improve drug delivery of anti-cancer drugs. Elsewhere, exciting developments in phosphazene-actinide chemistry have emerged: exotic examples of U(iv) complexes containing a well-defined UC bond have been prepared, which appear to demonstrate 3-centre P–C–U p-bonding, and covalent organic framework type networks prepared from N3P3Cl6 and phloroglucinol were shown to selectively separate (UO2)2+ from other metal ions. The same phosphorus precursor reacted with barbituric acid to give covalent organic networks capable of reducing carbon dioxide to methane under photocatalytic conditions. Chiral phosphazenes based on biaryl and P-spiro backbones were also reported to be effective in a number of catalytic enantioselective transformations.
Finally, we have another guest chapter from Professor Goutam Brahmachari, reviewing progress in green and energy-efficient synthetic approaches in organophosphorus chemistry in 2018, and extending the coverage of this topic in recent volumes.
D. W. Allen
L. J. Higham
J. C. Tebby