Dmitri Gelman

Ligand–Metal Cooperation in PCP Pincer Complexes: Rational Design and Catalytic Activity in Acceptorless Dehydrogenation of Alcohols

Cooperative ligands are non-innocent ligands that actively participate in reversible structural transformations of catalytic species over the course of a catalytic cycle. The ligand– metal cooperation often brings about unusual and exciting reactivity and plays a very important role in natural and artificial systems. Among others, this concept is of great interest for the design of new catalytic bond-breaking and bond-forming processes, as it offers a non-oxidative mechanistic alternative to the classical oxidative addition/reductive elimination sequence. The initial interest in this concept has been translated into practice, and efficient catalytic processes, which exploit conceptually different cooperating systems, have been discovered since the prominent reports on bifunctional hydrogenation catalysts by Noyori and co-workers (1; Figure 1)

Exploring the Reactivity of C(sp3)‐Cyclometalated IrIII Compounds in Hydrogen Transfer Reactions

The manuscript describes the synthesis and full characterization of a new PC(sp(3))P-based cyclometalated Ir(III) complex that manifests an exceptional thermal stability, as well as outstanding reactivity in hydrogen transfer reactions. The described compound represents the first example of a new family of stable C(sp(3))-metalated compounds.

Dichlorobis(triphenylphosphine)nickel-catalyzed cross-coupling of aryl chlorides with intramolecularly stabilized group 13 metal alkylating reagents

Abstract The intramolecularly stabilized alkyl and aryl aluminum complexes 1 , 4 and 11 , as well as the indium compounds 6 , 9 and 10 cross-couple with a variety of chloroarenes at 80°C in the presence of NiCl 2 (PPh 3 ) 2 to give selectively the respective alkylated arenes in high yields. Addition of organic or inorganic bases lowers the reaction temperature to 50°C.

Single-Component Phosphinous Acid Ruthenium(II) Catalysts for Versatile C−H Activation by Metal–Ligand Cooperation

Well-defined ruthenium(II) phosphinous acid (PA) complexes enabled chemo-, site-, and diastereoselective C-H functionalization of arenes and alkenes with ample scope. The outstanding catalytic activity was reflected by catalyst loadings as low as 0.75 mol %, and the most step-economical access reported to date to angiotensin II receptor antagonist blockbuster drugs. Mechanistic studies indicated a kinetically relevant C-X cleavage by a single-electron transfer (SET)-type elementary process, and provided evidence for a PA-assisted C-H ruthenation step.

Efficient synthesis of cyanohydrin trimethylsilyl ethers via 1,2-chemoselective cyanosilylation of carbonyls

Here we report a sustainable protocol for the cyanosilylation of carbonyl compounds 1a–g and 3a–m using trimethylsilyl cyanide and triphenylphosphine supported on polystyrene as a catalyst under solvent-free conditions. It has been shown that a small amount of the catalyst allows the chemoselective 1,2-addition of trimethylsilyl cyanide to α,β-unsaturated carbonyls 1a–g (5 mol%) and to saturated carbonyls 3a–m (2 mol%). The preparation of cyanohydrin trimethylsilyl ethers 2a–g and 4a–m has been accomplished in good yields (72–99%) and very low E-factor values (5–10). Finally, efficiency has been further improved by setting two different flow procedures that have allowed us to perform the representative preparation of cyanohydrin trimethylsilyl ether 4a on a large scale and with the E-factor of 0.16 or 0.47 consisting in a reduction of 90 or 72% of waste compared to our batch conditions.

PC(sp 3 )P Transition Metal Pincer Complexes: Properties and Catalytic Applications

Carbometalated pincer complexes represent a family of powerful compounds having tremendous number of manifold applications in organometallic chemistry, synthesis, catalysis, material science, and bioinorganic chemistry. This chapter reviews the recent developments in the chemistry and catalytic applications of PC(sp 3)P transition metal pincer complexes stressing their singular reactivity that stem from the unique electronic properties and topology.

Palladium-Catalyzed Cross-Methylation of Haloarenes Possessing Active Hydrogen Atoms by Intramolecularly Stabilized Dimethylindium and Dimethylaluminum Reagents

While the intramolecularly stabilized aluminum complex [(CH3)2AlOCH2CH2N(CH3)2]2 (2a) reacts readily with 4-bromophenol to give methane and [(4-BrC6H4O)2AlOCH2CH2N(CH3)2]2 (7), the demethylation of the analogous indium complex [(CH3)2InOCH2CH2N(CH3)2]22c is very slow. This inertness of 2c enables it to cross-methylate bromophenols and other bromoarenes with active hydrogen atoms in the presence of soluble palladium phosphane catalysts. The cross-methylation by 2c can be carried out under an ambient atmosphere. The ring-bound bromine atoms in 7 are replaced by CH3 groups when treated with an excess of the methylation reagent 2a, and the resulting aluminum cresolate liberates 4-methylphenol upon hydrolysis. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

2,2′-Bipyridine, 2-(2-oxazolyl)pyridine and 2,2′-bisoxazole derived nickel(0) complexes as selective catalysts for cross-coupling of aryl chlorides by intramolecularly stabilized dialkylaluminum reagents

Abstract Unlike the NiCl2(PPh3)2 catalyzed cross-coupling of chloroarenes with some intramolecularly stabilized dialkylaluminum reagents that is associated with hydrodehalogenation of the substrate, the phosphine-free bis(2,2′-bipyridine)nickel, bis[2-(4,5-dihydro-4,4-dimethyl-2-oxazolyl)pyridine)]nickel, bis[4,4′,5,5′-tetrahydro-4,4,4′,4′-tetramethyl-2,2′-bisoxazole]nickel and tetrakis(pyridine)nickel, promote the cross-coupling in a highly selective fashion. The reduction in the undesired hydrodechlorination by the nickel(0) complexes is explained by the presence of the nitrogen-containing ligands which stabilize the alkylnickel intermediate in the cross-coupling, against disproportionation into an alkene and nickel hydride. X-ray diffraction analyses of the reaction products of Ni(cod)2, chloroarene (or benzyl chloride) with 2,2′-bipyridine and with bis[2-(4,5-dihydro-4,4-dimethyl-2-oxazolyl)]pyridine, respectively, have been performed.

Synthesis, Structure, and Catalytic Activity of Some New Chiral 2-Menthylindenyl and 2-Menthyl-4,7-dimethylindenyl Rhodium Complexes

Optically active rhodium complexes containing the chiral, menthyl-substituted indenyl ligands (−)-2-menthyl-4,7-dimethylindene and (−)-2-menthylindene are described. Metathesis reactions of the chiral lithium salts of these indenyl systems with the appropriate starting materials yielded the complexes (−)-(2-menthyl-4,7-dimethylindenyl)Rh(CO)2 (2), (−)-(2-menthyl-4,7-dimethylindenyl)Rh(dppe) (3), (+)-(2-men- thylindenyl)Rh(dppe) (5), (−)-(2-menthylindenyl)Rh(PMe3)2 (6), and (−)-(2-menthylindenyl)Rh(nbd) (8). All compounds obtained were diastereomerically pure. The structures of 2, 3, and 6 were determined by single crystal X-ray diffractome- try. Complexes 3 as well as (−)-bis(η2-ethylene)(η5-2-menthyl-4,7-dimethylindenyl)rhodium(I) (9), (−)-(cycloocta-1,5-diene)(η5-1-menthyl-4,7-dimethylindenyl)rhodium(I) (10), (−)-(cycloocta-1,5-diene)(η5-2-menthyl-4,7-dimethylindenyl)rhodium(I) (11), and (−)-(cycloocta-1,5-diene)(η5-2-menthylindenyl)rhodium(I) (12) were found to be active as double bond hydrogenation catalysts. Two of them proved to induce asymmetry up to 18% ee. These complexes also promote the hydroformylation of olefins yielding both linear and branched aldehydes in varying ratios but hardly transfer chirality.

Kinetic resolution of racemic 2,2′-bis(trifluoromethane-sulfonyloxy)-1,1′-binaphthalene by chiral dimethylaluminum complexes and an achiral Pd catalyst, as well as by achiral dimethylaluminum reagents in the presence of a chiral Pd catalyst

Abstract Kinetic resolution of the racemic title compound was shown to take place during its methylation with either (Me 2 AlOCH 2 CH 2 OMe) 2 or Me 2 Al(CH 2 NMe 2 in the presence of an optically active Pd(binap) catalyst, as well as during its alkylation with either ( S )-(+)-[Me 2 AlOCH 2 CH(Me)OCH 2 Ph] 2 or ( S )-(+)-[Me 2 AlOCH 2 CH(CH 2 CHMe 2 )NMe 2 ] 2 in the presence of an achiral palladium complex. The ee values of the resolved binaphthyl derivatives by the two methods were up to 69 and 12%, respectively. The latter method represents the first application of a stabilized dialkylaluminum complex with a chiral chelating ligand for asymmetric induction.