Structurally characterized acylruthenium organometallics bearing a pendant aldehyde function

By reacting [Ru(RL¹)(PPh₃)₂(CO)Cl], (1) (R = C₆H₄Me, Et) with an excess of CNBu^t in the presence of NH₄PF₆, organometallics of the type [Ru(RL²)(PPh₃)₂(CNBu^t)₂]PF₆, (2) have been isolated in excellent yield [RL¹ = C₆H₂O-2-CHNHR(p)-3-Me-5, RL² = C₆H₂(CO)-O-2-CHNHR(p)-3-Me-5]. These organometallics, on controlled hydrolysis, produce [Ru(L³)(PPh₃)₂(CNBu^t)₂], (3) in very good yield (L³ = C₆H₂(CO)-O-CHO-3-Me-5). In both ([2(C₆H₄Me)] · 2H₂O) and ([3] · 2CH₂Cl₂) the two phosphine ligands lie in trans positions. In ([2(C₆H₄Me)] · 2H₂O) the Ru(C₆H₄MeL²) fragment, excluding the pendant tolyl ring, is a near perfect plane (mean dev ~ 0.02Å) which makes a dihedral angle of 5.2° with the tolyl plane. The acyl chelate ring in ([2(C₆H₄Me)] · 2H₂O) is excellently planar with a mean deviation of 0.006°. In ([3] · 2CH₂Cl₂) the Ru(L³) fragment defines a crystallographic plane of symmetry, the coordinates of the atom being of the type x, 1/4z. The complex ([2C₆H₄Me)] · 2H₂O) displays N–HȮFO (iminium-phenolato) hydrogen bonding while in ([3] · 2CH₂Cl₂) C–H...O hydrogen bonding is present. Characteristic spectral data (u.v.–vis, i.r. and ¹H n.m.r.) of the complexes are reported. A notable feature is that an allowed band near 500 nm due to the t_2g → π^*(azomethine) charge transfer transition, which is diagnostic of the coordinated iminium-phenolato function, is present in (3) but this band is absent in the aldehydic acyl complex (2). In the ¹H n.m.r. spectrum the N⁺–H signal in (2) (near 13.5 ppm) is split into a doublet due to transcoupling with the azomethine proton. The aldehydic proton of (3) resonates as a sharp singlet near 10 ppm. In CH₂Cl₂ solution (2) and (3) display quasireversible a Ru^III/Ru^IIcyclic voltammetric response with E_1/2 near 0.9 and 0.5 V versuss.c.e. The conversion (2) → (3) is accompanied by the nucleophilic attack of water. The complex (3) is also obtained directly from (1) by reaction with CNBu^t in the presence of H₂O. The aldehyde function in (3) is deactivated by the existing acyl moiety; as a result further decarbonylation does not take place.     

Selective functionalization of imidazoles via an iodine-copper exchange reaction

The reaction of protected 4,5-diiodoimidazoles with (PhMe2CCH2)2CuLi regioselectively provides 5-cuprated imidazoles, which readily react with various electrophiles furnishing functionalized imidazoles in good yields; remarkably, these resulting mono-iodoimidazoles undergo again an iodine-copper exchange reaction in the presence of sensitive functional groups, like an aldehyde or a ketone.     

Stereoselective functionalization of beta-iodo-alpha,beta-unsaturated ketones via an iodine-copper exchange reaction

[reaction: see text] Beta-iodo-alpha,beta-unsaturated carbonyl compounds undergo a stereoselective iodine-copper exchange reaction with (Nphyl)(2)CuLi, providing the corresponding alkenyl cuprates with retention of the double bond configuration. No competitive addition/elimination was observed, and the resulting cuprates were successfully functionalized with various electrophiles.     

Selective functionalization in positions 2 and 3 of indole via an iodine-copper exchange reaction

Two selectively successive I/Cu exchange reactions performed with (Nphyl)CuLi allow the functionalization of indoles in positions 2 and 3. The 2,3-diketones prepared by this method can readily be converted to tricyclic heterocycles by standard methods.     

Direct preparation of polyfunctional amino-substituted arylmagnesium reagents via an iodine-magnesium exchange reaction

The successive addition of PhMgCl and i-PrMgCl to functionalised iodoanilines allows their conversion to the corresponding amino-functionalised Grignard reagents, which react smoothly with a range of electrophiles in high yield.     

Stereoselective S N 2-substitutions using polyfunctional lithium arylcuprates prepared by an iodine-copper exchange

[reaction: see text] Polyfunctional mixed lithium arylcuprates of the type (FG-Ar)(PhMe(2)CCH(2))CuLi obtained via iodine- or bromine-copper exchange with (PhMe(2)CCH(2))(2)CuLi react with cyclic 2-iodoallylic acetates with high S(N)2 selectivity. The addition of ZnBr(2) changes this selectivity and allows the performance of highly regioselective and enantioselective anti S(N)2' substitutions using open-chain allylic pentafluorobenzoates.     

Enantioselective metallo-organocatalyzed preparation of cyclopentanes bearing an all-carbon quaternary stereocenter

Enantioselective metallo-organocatalyzed carbocyclizations of formyl-alkynes have been developed. The cooperation between aminocatalysis and a chiral copper(I) complex granted access to enantio-enriched cyclopentanes through the challenging formation of all-carbon quaternary stereocenters.     

Synthetic studies of pseurotin A: preparation of an advanced lactam aldehyde intermediate

An efficient synthesis of the lactam core of pseurotin A has been accomplished. Key features of this synthesis include a tandem oxidation-cyclization to form the lactam from an acetylenic amide precursor. Although coupling of a lactam aldehyde with an appropriate side chain was not effective, it is anticipated that incorporating a partial side chain at an earlier stage should permit completion of the total synthesis of pseurotin A.     

Stereospecific 2-vinylcyclohexanol formation via internal attack of an allylsilane moiety on an aldehyde group

Acid catalyzed cyclization of ($\text{E}$)-HCO-(CH₂)-₄-CH=C(Me)-CH(SPh)SiMe₃ affords $\text{cis}$-2-substituted cyclohexanol, while ($\text{Z}$) compound affords the $\text{trans}$ isomer. Those cyclized products are transformed to the corresponding α-methyl γ-lactones.     

New preparation of benzylic aluminum and zinc organometallics by direct insertion of aluminum powder

The reaction of commercial Al-powder (3 equiv) and InCl(3) (1-5 mol %) with benzylic chlorides provides various functionalized benzylic aluminum sesquichlorides under mild conditions (THF, 20 °C, 3-24 h) without homocoupling (<5%). These new benzylic organometallics reacted smoothly with various electrophiles (Pd-catalyzed cross-couplings, or Cu-mediated acylations, allylations, or 1,4-addition reactions). Electron-poor benzylic chlorides or substrates prone to Wurtz coupling can be converted to benzylic zinc compounds by the reaction of Al-powder in the presence of ZnCl(2).     

The preparation of hindered cuprates from aldehyde tosylhydrazones

Copper reagents react with secondary and tertiary aldehyde tosylhydrazones to give unique, hindered cuprates which are alkylated in a one-flask procedure.     

Synthesis of functionalized nitroarylmagnesium halides via an iodine-magnesium exchange

[reaction: see text] Various nitro-substituted aryl and heteroaryl iodides undergo an iodine-magnesium exchange reaction when treated with PhMgCl leading to nitro-containing magnesium organometallics. These Grignard reagents display an excellent stability at temperatures below -40 degrees C and do not undergo electron-transfer reactions. They react as expected with various electrophiles.     

Microwave-promoted three-component coupling of aldehyde, alkyne, and amine via C-H activation catalyzed by copper in water

[reaction: see text] An efficient three-component coupling of aldehyde, alkyne, and amine to generate propargylamines has been effected under microwave irradiation in water using only CuI catalyst without the noble metal cocatalyst. This method has proved to be applicable to a wide range of substrates. In addition, the preliminary experiment using (S)-proline methyl ester as a chiral source demonstrated that it could be developed to be a direct and highly diastereoselective method for construction of chiral propargylamines.     

Highly diastereoselective preparation of (E)-alkenylsilanes bearing an alpha-chiral center

The copper(I)-mediated anti-S(N)2' allylic substitution allows a highly stereoselective preparation of alkenylsilanes bearing a chiral center in the alpha-position with high transfer of chirality. These alkenylsilanes were converted into alpha,beta-unsaturated ketones or into the corresponding boronic esters without loss of the chiral information. [reaction: see text]     

Intramolecular 1,3-cycloadditions of nitrile ylides bearing an acetylenic function

Treatment of amides 1a,b with thionyl chloride followed by reaction with triethylamine gave 1,4-dihydro[1]benzopyrano[4,3-b]pyrrole derivatives ( 4a,b ) arising from intramolecular 1,3-cycloaddition of intermediate nitrile ylides ( 3a,b ).     

Preparation of 2-magnesiated 1,3,5-triazines via an iodine-magnesium exchange

Functionalized iodo- and diiodo-1,3,5-triazine derivatives readily undergo an I/Mg exchange with BuMgCl, sBuMgCl, or OctMgBr at low temperatures furnishing 2-magnesiated and 2-zincated 1,3,5-triazines (after transmetalation with ZnCl(2)). This method also offers a convenient access to dimagnesiated triazines. Furthermore, it allows the preparation of functionalized 1,3,5-triazinyl dimers and trimers, interesting for their opto-electronic properties.     

Preparation of functionalized zinc and copper organometallics containing sulfur functionalities at the alpha or gamma position

-Chloroalkyl phenyl sulfides1 readily insert zinc in THF at 25 °C (0.5–2 h), affording sulfur stabilized organozinc derivatives of type2. The presence of a functional group such as an ester or a cyano group is tolerated in these organometallics. After a transmetallation to the corresponding copper reagent3, they react with a wide range of electrophiles. Zinc and copper organometallics bearing a thiophenyl or a phenylsulfinyl group at the γ-position have also been prepared showing the generality of our approach.     

Determination of copper in white-metal bearing alloys

A method is proposed for the determination of copper in white-metal bearing alloys by direct controlled-potential electrolysis with a tantalum cathode at -0.32 V vs. SCE in a sulphate/bisulphate buffered electrolyte (pH 2) with fluoroboric acid and sodium tartrate as masking agents. Only Bi(III) interferes. Any co-deposited Bi can be corrected for by its spectrophotometric determination with Semi-Xylenol Orange after preconcentration with La(III) as carrier, from an ammoniacal solution containing the redissolved deposit. Any residual Cu(II) in the electrolyte is determined by spectrophotometry with 2,9-dimethyl-1, 10-phenanthroline. The standard deviation of this method has been found to be 0.03 mg (n = 12) and its relative standard deviation from 0.03 to 0.17%. It has been successfully used for referee analysis and certification of standard reference materials.     

Novel ferrocene-containing helical triangular macrocycle achieved via an exchange reaction

A novel ferrocene-containing helical triangular macrocyclic compound has been constructed through an exchange reaction of hydrazone groups which templated and catalyzed by Co(II) ions.