Alkylidinphosphane und -arsane. II. Über die Oxydation des Lithoxy-methylidinphosphans PC?O?Li mit Schwefeldioxid und Iod

Alkylidynephosphanes and -arsanes. II. Oxydation of Lithoxy-methylidynephosphane P?C? O? Li with Sulphur Dioxide and Iodine At ?50°C bis(1,2-dimethoxyethane-O,O′)lithoxymethylidynephosphane P?C? O? Li(dme)₂^1,2) ( 1 a ) [2] reacts almost quantitatively with sulphur dioxide or iodine in 1,2-dimethoxyethane solution to give bis(1,2-dimethoxyethane-O,O′)bis(tetrahydrofuran-O)(μ-1,2,4-triphospholo[1,2-a]-1,2,4-triphosphol-1,3,5,7-tetraonato(2?)-O¹,O⁷:O³,O⁵)dilithium ( 2 a ) and lithium dithionite or iodide respectively. From the reaction with sulphur dioxide the crystalline, pale yellow compound is obtained in 40% yield. The formation of the unusual anionic heterocycle, built up of four PCO units, may be explained by an oxydation of two [P?C? O]^? species first, followed by a nucleophilic attack of two other [P?C? O]^? anions and coupled ?intramolecular”? cycloaddition reactions. In the ³¹P{¹H} nmr spectrum two phosphorus atoms each of coordination number two and three give rise to two triplets with chemical shift values of 81.4 and 36.9 ppm and a ²J(PP) coupling constant of 31.7 Hz; the ¹³C{¹H} resonances of the [(PCO)₄]^2? anion come from an ABMM′X spin system, the X part being discussed in detail. An X-ray structure determination {Cmcm; a = 1 277.14(11); b = 1 487.7(2); c = 1 556.94(11) pm at ?100 ± 3°C; Z = 4 molecules; R₁ = 0.061; wR₂ = 0.150} shows compound 2 a to crystallize as a neutral complex of symmetry mm2. The anionic part of the molecule consists of two anellated 1,2-dihydro-5-oxo-1,2,4-triphosphol-3-olate rings which share the central P? P unit (P1? P1′ 215.3; P1–C1 189.1; C1 P2 178.4; C1 O1 123.9pm; C1? P1? P1′ 98.4; Cl? P1? C1″ 91.2; C1 P2 C1′ 98.7°). Thus compound 2a may be assigned to the group of P? P heterocycles with a butterfly structure [71–75] as well as to the well-known diacylphosphanides taking into account, however, the unusual E,E configuration of both O?C? P?C? O^? units. The lithium cations are square pyramidally coordinate (Li? O 193.5 to 209.1 pm), each additionally binding an 1,2-dimethoxyethane and a tetrahydrofuran molecule.     

Sulfoximid und Sulfoximidium-Salze – Strukturen und H?Brückenbindungen

Sulfoximide and Sulfoximidium Salts – Structures and Hydrogen Bonding In the solid state dimethylsulfoximide ( 1 ) (orthorhombic; space group Pbca; a = 577.8, b = 931.2 and c = 1645.6 pm) makes intermolecular N? H ? N hydrogen bonds. The hydrogen halide salts (CH₃)₂S(O)NH₂⁺Hal^? (( 2 ), Hal^??Cl^?; ( 4 ), Hal^??Br^?) reacts with metal halides to yield (CH₃)₂S(O)NH₂⁺MHal with the complex anions (( 5 ), MHal?SbCl₄^?; ( 6 ), MHal?SbCl₅^2?; ( 7 ), MHal?SbCl₆^?; ( 8 ), MHal?SbBr₅^2?; ( 9 ), MHal?AlCl₄^?). 2 crystallizes from ethanol (96%) as [(CH₃)₂S(O)NH₂⁺Cl^?]₂ · H₂O ( 3 ). The structures of 3 (monoclinic; space group P2₁/c; a = 917.0, b = 1344.7, c = 1080.8 pm and β = 103.8°; Z = 10), 4 (orthorhombic; space group Pbcn; a = 1028.9, b = 1132.6, c = 1074.1 pm; Z = 8) and 6 (monoclinic; space group C2/c; a = 2041.1, b = 1101.4, c = 3365.6 pm and β = 153.8°; Z = 8) are determined by X-ray analysis. In 6 Sb is coordinated in a distorted octahedra by 6 Cl in three short (mean 245,5 pm; SbCl₃) and three long distances (291 to 299 pm; Cl^?). Two of the chloride ions connect the Sb atoms to infinite Sb …? Cl …? Sb chains. Except for 7 and 9 there are bridges between the NH₂ groups and the halide ions. The NH valence vibrations are discussed in view of hydrogen bonding.     

An efficient synthesis of phosphenimidous esters,RO?PN?Ar

Trimethylsilyltrifluoromethane sulfonate is shown to be an efficient catalyst for the elimination of Me₃SiCl from N-trimethylsilyl-N-(2,4,6-tri-tert-butylphenyl)amidochlorophosphites la-f , leading to the phosphenimidous esters 3a–f. The crystal structures of phosphites 1a and 1d provide a stereochemical explanation for the better thermal stability of 1d On the basis of these observations a convenient and general synthesis of phosphenimidous esters 3a–f is presented.     

Attempted 1,3-trimethylsilyl migration in Me3Si?PSN?R system

A dimer of thioxo-N-t-butylimino(trimethylsiloxy)-phosphorane 5 has been prepared by reaction of tris(trimethylsilyl) phosphine with N-sulfinyl-N-tert-butylamine. The structure of 5 has been confimed by X-ray analysis data. 1-Aza-2-thia-3-phosphaallene 1 , thiaphosphaziridine 3 , iminophosphine P-sulfide 4 are postulated as intermediates of the reaction studied.     

The Liebeskind–Srogl C?C Cross‐Coupling Reaction

New kid on the block : The cross‐coupling of thioorganic compounds with boronic acids under neutral conditions in the presence of catalytic palladium(0) and a stoichiometric amount of a copper(I) oxygenate has emerged as a very useful method for the construction of C C bonds (see scheme). This intriguing and mechanistically unprecedented base‐free coupling has distinct advantages, in particular when traditional Pd⁰‐catalyzed cross‐coupling is not possible.

     

Evidence for C?Cl/C?Br⋅⋅⋅π Interactions as an Important Contribution to Protein–Ligand Binding Affinity

Attractive chlorine : Noncovalent interactions between chlorine or bromine atoms and aromatic rings in proteins open up a new method for the manipulation of molecular recognition. Substitution at distinct positions of two factor Xa inhibitors improves the free energy of binding by interaction with a tyrosine unit. The generality of this motif was underscored by multiple crystal structures as well as high‐level quantum chemical calculations (see picture).

     

Evidence for C?Cl/C?Br⋅⋅⋅π Interactions as an Important Contribution to Protein–Ligand Binding Affinity

Attraktives Chlor : Nichtkovalente Wechselwirkungen zwischen Chlor‐ oder Brom‐Atomen und aromatischen Ringen in Proteinen bieten einen neuen Ansatzpunkt für die Beeinflussung der molekularen Erkennung. Die Einführung dieser Substituenten an spezifischen Positionen zweier Faktor‐Xa‐Inhibitoren erhöht deren freie Bindungsenergie durch die Wechselwirkung mit einer Tyrosineinheit. Das allgemeine Vorkommen dieses Strukturmotivs wird anhand zahlreicher Kristallstukturen und quantenchemischer Rechnungen belegt (siehe Bild).

     

Metal‐Catalyzed α‐Arylation of Carbonyl and Related Molecules: Novel Trends in C?C Bond Formation by C?H Bond Functionalization

α‐Arylated carbonyl compounds are commonly occurring motifs in biologically interesting molecules and are therefore of high interest to the pharmaceutical industry. Conventional procedures for their synthesis often result in complications in scale‐up, such as the use of stoichiometric amounts of toxic reagents and harsh reaction conditions. Over the last decade, significant efforts have been directed towards the development of metal‐catalyzed α‐arylations of carbonyl compounds as an alternative synthetic approach that operates under milder conditions. This Review summarizes the developments in this area to date, with a focus on how the substrate scope has been expanded through selection of the most appropriate synthetic method, such as the careful choice of ligands, precatalysts, bases, and reaction conditions.     

Palladium(II)‐Catalyzed C?H Activation/C?C Cross‐Coupling Reactions: Versatility and Practicality

Pick your Pd partners : A number of catalytic systems have been developed for palladium‐catalyzed C? H activation/C? C bond formation. Recent studies concerning the palladium(II)‐catalyzed coupling of C? H bonds with organometallic reagents through a Pd^II/Pd⁰ catalytic cycle are discussed (see scheme), and the versatility and practicality of this new mode of catalysis are presented. Unaddressed questions and the potential for development in the field are also addressed.

     

Rhodium(III)‐Catalyzed C?C and C?O Coupling of Quinoline N‐Oxides with Alkynes: Combination of C?H Activation with O‐Atom Transfer

[Cp*Rh^III]‐catalyzed C H activation of arenes assisted by an oxidizing N O or N N directing group has allowed the construction of a number of hetercycles. In contrast, a polar N O bond is well‐known to undergo O‐atom transfer (OAT) to alkynes. Despite the liability of N O bonds in both C H activation and OAT, these two important areas evolved separately. In this report, [Cp*Rh^III] catalysts integrate both areas in an efficient redox‐neutral coupling of quinoline N‐oxides with alkynes to afford α‐(8‐quinolyl)acetophenones. In this process the N O bond acts as both a directing group for C H activation and as an O‐atom donor.