Coordination Chemistry of the (eta(6)-p-Cymene)ruthenium(II) Fragment with Bis-, Tris-, andTetrakis(pyrazol-1-yl)borate Ligands: Synthesis, Structural, Electrochemical, and CatalyticDiastereoselective Nitroaldol Reaction Studies

Novel [Ru(eta(6)-p-cymene)(kappa(2)-L)X] and [Ru(eta(6)-p-cymene)(kappa(3)-L)]X center dot nH(2)O complexes (L = bis-, tris-, or tetrakis-pyrazolylborate; X = Cl, N-3, PF6, or CF3SO3) are prepared by treatment of [Ru(eta(6)-p-cymene)Cl-2](2) with poly-(pyrazolyl)borate derivatives [M(L)] (L in general; in detail L = Ph(2)Bp = diphenylbis-(pyrazol-1-yl)borate; L = Tp = hydrotris(pyrazol-1-yl)borate; L = pzTp = tetrakis(pyrazol-1-yl)borate; L = Tp(4Bo) = hydrotris(indazol-1-yl)borate, L = T-p4Bo,T-5Me = (5-methylindazol-1-yl)borate; L = Tp(Bn,4Ph) = hydrotris(3-benzyl-4-phenylpyrazol-1-yl)borate; M = Na, K, or TI) and characterized by analytical and spectral data (IR, ESIMS, H-1 and C-13 NMR). The structures of [Ru(eta(6)-p-cymene)(Ph(2)Bp)Cl] (1) and [Ru(eta(6)-p-cymene)(Tp)Cl] (3) have been established by single-crystal X-ray diffraction analysis. Electrochemical studies allowed comparing the electron-donor characters of Tp and related ligands and estimating the corresponding values of the Lever E-L ligand parameter. The complexes [Ru(eta(6)-p-cymene)-(kappa(2)-L)X] and [Ru(eta(6)-p-cymene)(kappa(3)-L)]X center dot nH(2)O act as catalyst precursors for the diastereoselective nitroaldol reaction of benzaldehyde and nitroethane to the corresponding beta-nitroalkanol (up to 82% yield, at room temperature) with diastereoselectivity toward the formation of the threo isomer

Allylic alcohols: Valuable synthetic equivalents of non-activated alkenes in gold-catalyzed enantioselective alkylation of indoles

none6The recent booming of gold catalysis has demonstrated that unprecedented transformations can be realized in a highly selective manner. Moreover, due to the growing availability of chiral organic ligands, gold-catalysis can be considered as one of most dynamic hot spots in asymmetric synthesis. However, in this context, the use of non-activated olefinic CeC double bonds is still largely unexplored due to the intrinsic inertness of C]C (respect to allenes and alkynes) in taking part in nucleophilic additions assisted by p-electrophilic activations. Allylic alcohols have been demonstrated to be feasible “surrogates” of non-activated alkenes for the enantioselective allylic alkylation of indoles catalyzed by chiral gold(I) complexes. In this investigation, a full account addressing efficiency and substrate scope of such a process is presented.openM. Bandini; A. Gualandi; M. Monari; A. Romaniello; D. Savoia; M. TragniM. Bandini; A. Gualandi; M. Monari; A. Romaniello; D. Savoia; M. Tragn

Allylic and Allenylic Dearomatization of Indoles promoted by Graphene Oxide via Covalent Grafting Activation Mode

The site‐selective allylative and allenylative dearomatization of indoles with alcohols is performed under carbocatalytic regime in the presence of graphene oxide (GO, 10 wt% loading) as the promoter. Metal‐free conditions, absence of stoichiometric additive, environmentally friendly conditions (H2O/CH3CN, 55 \ub0C, 6 h), broad substrate scope (33 examples, yield up to 92%) and excellent site‐ and stereoselectivity characterize the present methodology. Moreover, a covalent activation model exerted by GO functionalities was corroborated by spectroscopic, experimental and computational evidences. Recovering and regeneration of the GO catalyst via simple acidic treatment was also documented

Reinvestigation of the tautomerism of some substituted 2-hydroxypyridines

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Nickel Catalyzed Carbonylation/Carboxylation Sequence via Double CO2 Incorporation

A carbonylation/carboxylation synthetic sequence, via double CO2 fixation, is described. The productive merger of a Ni-catalyzed cross-electrophile coupling manifold with the use of AlCl3, triggered a cascade reaction with the formation of three consecutive C-C bonds, in a one single operation. This strategy traces an unprecedented synthetic route to ketones under Lewis acid assisted carbon dioxide valorization. Computational insights revealed a unique double function of AlCl3 and labeling (13CO2) experiments validate the genuine incorporation of CO2 in both functional groups

Fast MacMillan's Imidazolidinone-Catalyzed Enantioselective Synthesis of Polyfunctionalized 4-Isoxazoline Scaffolds

The enantioselective 1,3-dipolar cycloaddition of nitrones and arylpropionaldehydes to generate highly functionalized scaffolds for application in drug discovery was herein investigated. The use of a second-generation MacMillan catalyst as hydrochloride salt consistently accelerated the reaction speed, allowing a decrease in the reaction time up to >100 times, still affording 4-isoxazolines with good to excellent enantiomeric ratios at room temperature. As a proof of concept, further functionalization of the isoxazoline core through Pd-catalyzed cross-coupling was performed, generating differently functionalized chemical architectures in high yield

A pyrazine amide – 4-aminoquinoline hybrid and its rhodium and iridium pentamethylcyclopentadienyl complexes; evaluation of anti-mycobacterial and anti-plasmodial activities

The synthesis and characterization of N-(2-((7-chloroquinolin-4-yl)amino)ethyl)pyrazine-2-carboxamide (L), an aminoquinoline – pyrazinamide hybrid, and the complexes (N-(2-((7-chloroquinolin-4-yl)amino)ethyl)pyrazine-2-carboxamide)(cyclopentadienyl) chlorido-rhodium or iridium hexafluorophosphate ([M(L)(Cp*)Cl] PF6; M = Rh, Ir) and the corresponding chlorido salts ([M(L)(Cp*) Cl]Cl; M = Rh, Ir) are described. The ligand and the hexafluorophosphate salts of the metal complexes have been evaluated for anti-plasmodial and anti-mycobacterial activity. The rhodium and the iridium complexes were significantly more active against M. tuberculosis than the free ligand. The crystallographically determined molecular structures of complexes (N-(2-((7-chloroquinolin-4-yl)amino)ethyl)pyrazine-2-carboxamide)(cyclopentadienyl)chlororhodium hexafluoro-phosphate and (N-(2-((7-chloroquinolin-4-yl)amino)ethyl)pyrazine-2-carboxamide)(cyclopentadienyl)chloro-iridium chloride are presented