Current Organic Chemistry - Volume 10, Issue 1, 2006

The Editor-in-Chief and the management of Current Organic Chemistry decided to devote a special issue to Organophosphorus Chemistry in 2005, to be followed by two more thematic issues in 2006 and 2007. The dedication of one special issue to organophosphorus chemistry, among the annual 18 issues, is a clear recognition of the importance of this subject, the recent trends and achievements of which can be surveyed at www.icpc2004.com (the website of the most recent International Conference on Phosphorus Chemistry). The organophosphorus chemistry covered by the articles of this issue includes highlighted topics in bioorganic chemistry, organometallic chemistry, asymmetric synthesis (catalysis) supramolecular chemistry and heterocyclic chemistry. These days the medicinal aspects of organophosphorus compounds are indeed in focus, the group of compounds with anticancer and antiviral activity forms one of the majos fields. The use of computer-aided design in the development of novel phosphonic and phosphinic acids as enzyme inhibitors, in both the agrochemical and biomedical fields, is ananother active field of research. Phosphines are widely applied as ligands in transition metal complexes. A special and environmentally friendly method for the preparation of phosphines involves hydrophosphination. The most convenient precursors of P(III)-ligands are the corresponding boranes. The synthesis and utilisation of borane complexes of trivalent phosphorus acids is a brand new field. The coordination chemistry of cyano-substituted phosphines and heterocyclic phosphines, such as phosphinines represents a promising discipline also from the point of view of catalytic applications of transition metals. Macrocycles combined with special chelating -C(O)NHP(O)-moieties may be special complexants towards a variety of metal cations. The P-heterocyclic field has become one of the most dynamically developing branches of organophosphorus chemistry. Thus, 5- and 6-membered P-heterocycles, as well as bridged derivatives form representative groups of ring phosphorus compounds. The newer developments of phosphole, and of dihydro- and tetrahydrophosphinine chemistry, are of interest from a number of points of view. Bridged 1,2-oxaphosphabicyclo[2.2.2]octene 2-oxides are precursors of metaphosphonates, useful in phosphonylations. The 1. Organophosphorus Special Issue has been divided into two parts published back to back. The five reviews included in this issue (Part B) have been preceded by five other articles in Volume 9, Number 18 (Part A). The previous papers are the following: Organophosphorus Chemistry: Therapeutic Intervention in Mechanisms of Viral and Cellular Replication by Nick J. Wardle, S. W. Annie Bligh and Harry R. Hudson Computer-Aided Analysis and Design of Phosphonic and Phosphinic Enzyme Inhibitors as Potential Drugs and Agrochemicals by Lukasz Berlicki and Pawel Kafarski Hydrophosphination of Unactivated Alkenes, Alkynes and Allenes: A Versatile and Valuable Approach for the Synthesis of Phosphines by O. Delacroix and Annie-Claude Gaumont Phosphinous Acid-Boranes by K. Michal Pietrusiewicz and Marek Stankevic Synthesis and Coordination Chemistry of Cyanosubstituted Phosphines by Irina L. Odinets, Natalya M. Vinogradova, Ekaterina V. Matveeva and Tatyana A. Mastryukova

This review deals with the chemistry of phosphinines. As many reviews are available on the syntheses of these derivatives, only the most versatile methods are presented, or the ones giving access to the phosphinines that have been particularly studied. Then, recent results obtained in the coordination chemistry of phosphinines are summarized with an emphasis on their analogy with CO ligands. Indeed, the first studies proved these ligands to be well adapted for the stabilization of electron rich metal centers. Shortly after, highly reduced complexes have been obtained through the reaction of reduced 2,2'-biphosphinine dianions with transition metal fragments. Theoretical calculations were performed to establish the oxidation state of the metal in these complexes. On the other hand, the various coordination studies have pointed out that phosphinines become sensitive toward nucleophiles once they are bound to (even slightly) oxidized metal centers. This sensitivity precluded their use in most catalytic processes, but the cases in which they could be used efficiently are presented in this review. Two ways to circumvent this drawback were developed lately. The first method relies on the use of the high electrophilicity of the phosphorus atom of the phosphinine moiety. The ring is readily transformed into phosphacyclohexadienyl anions, which exhibit surprising coordination chemistry and promising behavior in catalysis. Results in this domain are presented. The second method is based on the involvement of the ring, as phosphadiene, into [4+2] Diels Alder type cycloadditions leading to phosphabarrelene derivatives. These ligands also show promising results in catalytic processes. Finally, phosphinines have been used successfully to stabilize gold nanoparticles, which opens a whole new field of applications for these ligands.

N-Acylamidophosphinates RC(X)NHP(Y)R'2 (NAAP) and their thioanalogues (X,Y= O, S; R = Alk, Ar, CCl3, Het, NR2 2, NR2R3; R' = Ar, OAlk, OAr, SAlk, NAlk2, NHAr) contain X, Y donor atoms and amide nitrogen, which are capable of taking in complexation with metal cations. An application of NAAP complexes in supramolecular chemistry has been investigated in the last decades. Developed synthetic methods allow us to obtain N-acylamidophosphinate ligands contained multiple chelating groups or a combination of several essentially various coordinating fragments in the molecule: chelating moiety C(X)NHP(Y) and a macrocycle. The latter ligands are capable of connecting ions simultaneously by the chelating sites, and by the "guest-host" mechanism using the macrocycle. The bibliography includes 104 references.

The last five years have seen many advances in the chemistry of phospholes. Motivating much of the work has been the potential for discovering valuable applications of phospholes, especially as ligands in metal coordination compounds designed for use as homogeneous catalysts, and in the field of electro-optical substances. This review covers the research in the synthesis, properties and applications of phospholes that has been published since the last comprehensive review by the author in 1999. While prepared for the specialist, the review is designed to introduce some of the aspects of phosphole chemistry to the general reader.

The 2-phosphabicyclo[2.2.2]octene and 2,3-oxaphosphabicyclo[2.2.2]octene systems undergo fragmentation in inert solvents on heating, or by UV-irradiation at room or low temperature. The fragmentation is of significance because it leads to the extrusion of low-coordinated species Y-P(X)O (Y = RO, R2N, Aryl; X = O, S, CH2), which are very effective phosphorylating agents. This review covers different aspects of the 2-phosphabicyclo[2.2.2]octene and 2,3-oxaphosphabicyclo[2.2.2]octene derivatives. The first part is focused on their synthesis and structure. The reactivity of 2,3-oxaphosphabicyclooctenes involving rearrangement and fragmentation with release of the bridging P-O unit including mechanistic studies is described in the next part. The last part of the review is dedicated to the practical aspects of the utilization these compounds as phosphorylating agents.

The members of a logically built P-heterocyclic family are discussed systematically to show a dynamically developing discipline of organophosphorus chemistry. Dichlorocyclopropanation of 2,5-dihydro-1H-phosphole oxides led to 3-phosphabicyclo[3.1.0]hexane 3-oxides that were useful intermediates for the synthesis of ring expanded products, such as 1,2-dihydrophosphinine oxides and 3-alkoxy-1,2,3,6-tetrahydrophosphinine oxides. Catalytic hydrogenation of 1,2-dihydrophosphinine oxides gave 1,2,3,4,5,6-hexahydrophosphinine oxides. Selective reduction of the α,β-doublebond of 1,2-dihydrophosphinine oxides via hydroboration led to 1,2,3,6-tetrahydrophosphinine oxides. Michael addition of >P(O)H species to the electron-poor double-bond of 1,2-dihydrophosphinine oxides afforded 1,2,3,6- tetrahydrophosphinine oxides with exocyclic P-function in position 3. Hydrogenation of these P-heterocycles led to the corresponding hexahydrophosphinine oxides. Stereostructure and conformation of the tetra- and hexahydrophosphinine oxides were elucidated by stereospecific NMR couplings and/or quantum chemical calculations. After deoxygenation, some of the above P-heterocycles were suitable P-ligands in transition metal complexes. The 1,2-dihydrophosphinine oxides were also useful in the synthesis of aromatic phosphinines, phosphepine derivatives and phosphabicyclo[2.2.2]octene oxides, as well as hetrocyclic β-oxophosphoranes.