Intramolecular metathesis versus Kharasch reactions using the Grubbs metathesis catalyst: towards catalyst economy

Crystal structure of catena-poly[hemi[1,3-bis-(2,6-diisoprop-ylphenyl)imidazolium] [[μ3-acetato-κ(3) O:O:O'-tri-μ2-acetato-κ(6) O:O'-dicopper(II)(Cu-Cu)]-μ-chlorido] di-chloro-methane sesqui-solvate]

The title copper(II) complex, {(C27H37N2)[Cu4(CH3COO)8Cl]·3CH2Cl2} n , is a one-dimensional coordination polymer. The asymmetric unit is composed of a copper(II) tetra-acetate paddle-wheel complex, a Cl(-) anion situated on a twofold rotation axis, half a 1,3-bis-(2,6-diisoprop-ylphenyl)imidazolium cation (the whole mol-ecule being generated by twofold rotation symmetry) and one and a half of a di-chloro-methane solvent mol-ecule (one being located about a twofold rotation axis). The central metal-organic framework comprises of a tetra-nuclear copper(II) acetate 'paddle-wheel' complex which arises from the dimerization of the copper(II) tetra-acetate core comprising of three μ2-bidentate acetate and one μ3-tridentate acetate ligands per binuclear paddle-wheel complex. Both Cu(II) atoms of the binuclear component adopt a distorted square-pyramidal coordination geometry (τ = 0.04), with a Cu⋯Cu separation of 2.6016 (2) Å. The apical coordination site of one Cu(II) atom is occupied by an O atom of a neighbouring acetate bridge [Cu-O = 2.200 (2) Å], while that of the second Cu(II) atom is occupied by a bridging chloride ligand [Cu⋯Cl = 2.4364 (4) Å]. The chloride bridge is slightly bent with respect to the Cu⋯Cu inter-nuclear axis [Cu-Cl-Cu = 167.06 (6)°] and the tetra-nuclear units are located about a twofold rotation axis, forming the one-dimensional polymer that propagates along [101]. Charge neutrality is maintained by the inclusion of the 1,3-bis-(2,6-diisoprop-ylphenyl)imidazolium cation within the crystal lattice. In the crystal, the cation and di-chloro-methane solvent mol-ecules are linked to the coordin-ation polymer by various C-H⋯O and C-H⋯Cl hydrogen bonds. There are no other significant inter-molecular inter-actions present.

Atom transfer radical cyclization of trichloroacetamides to electron-rich acceptors using Grubbs' catalysts: synthesis of the tricyclic framework of FR901483

Intramolecular Kharasch-type additions of trichloroacetamides on anisole and enol acetates catalyzed by Grubbs' ruthenium carbenes are described. This protocol provides access to highly functionalized 2-azaspiro[4.5]decanes, morphan compounds, and the azatricyclic core of FR901483.

Tandem catalysis in domino olefin cross-metathesis/intramolecular oxa-conjugate cyclization: concise synthesis of 2,6-cis-substituted tetrahydropyran derivatives

Herein, we describe the concise synthesis of 2,6-cis-substituted tetrahydropyran derivatives based on a domino olefin cross-metathesis/intramolecular oxa-conjugate cyclization (CM/IOCC) reaction. We have found that the domino CM/IOCC of δ-hydroxy olefins with α,β-unsaturated carbonyl compounds (e.g., trans-crotonaldehyde or N-acryloyl-2,5-dimethylpyrrole) could be efficiently achieved in the presence of the second-generation Hoveyda-Grubbs catalyst under elevated temperature conditions, directly affording 2,6-cis-substituted tetrahydropyrans in excellent yields with synthetically useful diastereoselectivity ("auto-tandem catalysis"). In addition, we have found that the domino CM/IOCC of δ-hydroxy olefins with α,β-unsaturated carbonyl compounds could be achieved simply by performing CM in the presence of a Brønsted acid in CH(2)Cl(2) at 25-35 °C, which delivered 2,6-cis-substituted tetrahydropyrans in good yields with excellent diastereoselectivity ("orthogonal-tandem catalysis"). To understand the mechanism of auto-tandem catalysis in the domino CM/IOCC reaction, we have investigated the role of ruthenium hydride complexes in the IOCC of a ζ-hydroxy α,β-unsaturated ketone as a model case.

Radicals in transition metal catalyzed reactions? transition metal catalyzed radical reactions? - a fruitful interplay anyway: part 2. Radical catalysis by group 8 and 9 elements

This review summarizes the current status of transition metal catalyzed reactions involving radical intermediates in organic chemistry. This part focuses on radical-based methods catalyzed by group 8 and group 9 metal complexes. Reductive and redox-neutral coupling methods catalyzed by low-valent metal complexes as well as catalytic oxidative C-C bond formations are reviewed.

Atom-Transfer Radical Addition (ATRA) and Cyclization (ATRC) Reactions Catalyzed by a Mixture of [RuCl2Cp*(PPh3)] and Magnesium

A new catalytic procedure for atom-transfer radical addition (ATRA) and cyclization (ATRC) reactions is described. The combination of the ruthenium(III) complex [RuCl(2)Cp*(PPh3)] (Cp*: pentamethylcyclopentadienyl) with magnesium allows these reactions to be performed under mild conditions with high efficiency. In most cases, the catalyst concentrations required are significantly lower than those used in previously reported procedures. It is suggested that magnesium acts as a reducing agent that generates and regenerates the catalytically active ruthenium(II) species. The precatalyst [RuCl(2)Cp*(PPh3)] has been analyzed by X-ray crystallography.

A practical ruthenium-catalyzed cleavage of the allyl protecting group in amides, lactams, imides, and congeners

A convenient methodology for the deprotection of N-allylic amide-like moieties was developed. The first examples accounting for the ruthenium-catalyzed deallylation of amides, lactams, imides, pyrazolidones, hydantoins, and oxazolidinones have been achieved by the sequential use of Grubbs carbene (isomerization step) and RuCl(3) (oxidation step). A variety of substrates, including enantiopure multifunctional beta- and gamma-lactams, can be employed.