Synthesis of Highly Fluorinated Arene Complexes of [Rh(Chelating Phosphine)]+ Cations,and their use in Synthesis and Catalysis

The synthesis of rhodium complexes with weakly binding highly fluorinated benzene ligands is described: 1,2,3-F₃C₆H₃, 1,2,3,4-F₄C₆H₂ and 1,2,3,4,5-F₅C₆H are shown to bind with cationic [Rh(Cy₂P(CH₂)_xPCy₂)]⁺ fragments (x=1, 2). Their structures and reactivity with alkenes, and use in catalysis for promoting the Tishchenko reaction of a simple aldehyde, are demonstrated. Key to the synthesis of these complexes is the highly concentrated reaction conditions and use of the [Al{OC(CF₃)₃}₄]⁻ anion.     

Combining Organometallic Reagents,the Sulfur Dioxide Surrogate DABSO,and Amines: A One‐Pot Preparation of Sulfonamides,Amenable to Array Synthesis

We describe a method for the synthesis of sulfonamides through the combination of an organometallic reagent, a sulfur dioxide equivalent, and an aqueous solution of an amine under oxidative conditions (bleach). This simple reaction protocol avoids the need to employ sulfonyl chloride substrates, thus removing the limitation imposed by the commercial availability of these reagents. The resultant method allows access to new chemical space, and is also tolerant of the polar functional groups needed to impart favorable physiochemical properties required for medicinal chemistry and agrochemistry. The developed chemistry is employed in the synthesis of a targeted 70 compound array, prepared using automated methods. The array achieved a 93 % success rate for compounds prepared. Calculated molecular weights, lipophilicities, and polar surface areas are presented, demonstrating the utility of the method for delivering sulfonamides with drug‐like properties.     

A formal total synthesis of platencin

The readily available and enantiomerically pure trienes 12 undergo a thermally induced intramolecular Diels-Alder reaction to give the corresponding mixture of compounds 13 and 14. This mixture has been elaborated to an advanced intermediate associated with Nicolaou's recently reported total synthesis of the natural enantiomeric form of the antibiotic platencin (2).     

A chemoenzymatic total synthesis of the structure assigned to the alkaloid (+)-montabuphine

An enantioselective synthesis of the structure, 3, assigned to the alkaloid (+)-montabuphine has been achieved using the readily available metabolite 4 as starting material. A comparison of the physical and spectral data recorded on compound 3 with those reported for (+)-montabuphine suggests that they are different compounds.     

Isoselenocarbonyls via acetylenic C-Se activation

The first examples of isoselenocarbonyl linked bimetallics arise from the chemoselective insertion of platinum(0) into the alkynyl-selenium bond of a molybdenum alkynylselenolatoalkyidyne complex.     

Ruthenium complexes of substituted hydrazine: new solution- and solid-state binding modes

The methylhydrazine complex [Ru(NH(2)NHMe)(PyP)(2)]Cl(BPh(4)) (PyP=1-[2-(diphenylphosphino)ethyl]pyrazole) was synthesised by addition of methylhydrazine to the bimetallic complex [Ru(mu-Cl)(PyP)(2)](2)(BPh(4))(2). The methylhydrazine ligand of the ruthenium complex has two different binding modes: side-on (eta(2)-) when the complex is in the solid state and end-on (eta(1)-) when the complex is in solution. The solid-state structure of [Ru(PyP)(2)(NH(2)NHMe)]Cl(BPh(4)) was determined by X-ray crystallography. 2D NMR spectroscopic experiments with (15)N at natural abundance confirmed that in solution the methylhydrazine is bound to the metal centre by only the -NH(2) group and the ruthenium complex retains an octahedral conformation. Hydrazine complexes [RuCl(PyP)(2)(eta(1)-NH(2)NRR')]OSO(2)CF(3) (in which R=H, R'=Ph, R=R'=Me and NRR'=NC(5)H(10)) were formed in situ by the addition of phenylhydrazine, 1,1-dimethylhydrazine and N-aminopiperidine, respectively, to a solution of the bimetallic complex [Ru(mu-Cl)(PyP)(2)](2)(OSO(2)CF(3))(2) in dichloromethane. These substituted hydrazine complexes of ruthenium were shown to exist in an equilibrium mixture with the bimetallic starting material.     

Inorganic asymmetric synthesis: diastereoselective syntheses of mono- and dinuclear complexes containing octahedral, two-bladed propeller, bis(pyridine-2-aldehyde 2'-pyridylhydrazone)iron(II) stereocenters

A C2 hexadentate diester derived from (5-hydroxymethyl)pyridine-2-aldehyde 2'-pyridylhydrazone (5-HOCH2PAPHY) and an enantiomerically pure (aS)-spirane dicarboxylic acid diastereoselectively reacts with iron(II) benzenesulfonate in methanol to furnish a 20% diastereomeric excess (de) of a two-bladed propeller, octahedral iron complex in which the P configuration of the newly created (+/-)-[Fe(PAPHY)2](2+) stereocenter predominates; when the reaction mixture is heated under reflux for 12 h, however, the excess of the diastereomer having the P configuration at iron increases to 80%, as determined by (1)H NMR spectroscopy. The configuration at iron in the major diastereomer of the complex was determined by comparison of the circular dichroism spectrum of the deprotonated complex with that of a related complex of known configuration. Repositioning of the hydroxymethyl group of the pyridine-2-aldehyde from the 5- to the 6-position produced a C2-spirane ligand that generates a double-stranded diiron(II) helicate in >99% de. Single crystal X-ray structure determinations of the racemates of the protonated and deprotonated helicates revealed that the complexes crystallize diastereoselectively, that is, two ligand strands of a S configuration generate two octahedral iron(II) stereocenters of P configuration to give a dinuclear metal helicate of P configuration and vice versa for the ligand of a R configuration.     

Direct Cross‐Couplings of Propargylic Diols

[Pd(PPh₃)₄] catalyzes a Suzuki–Miyaura‐like twofold cross‐coupling sequence between underivatized propargylic diols and either aryl or alkenyl boronic acids to furnish highly substituted 1,3‐dienes. Thus, 2,3‐diaryl‐1,3‐butadienes and their dialkenic congeners ([4]dendralenes) are delivered in a (pseudo)halogen‐free, single‐step synthesis which supersedes existing methods. Allenols are also readily formed. Treatment of these single‐ and twofold cross‐coupled products with acid leads to remarkably short syntheses of highly‐substituted benzofulvenes and aryl indenes, respectively.