Rafael E. Rodríguez-Lugo

Direct Amidation of Aldehydes with Primary Amines under Mild Conditions Catalyzed by Diolefin‐Amine–RhI Complexes

The development of methods for the simple and economical syntheses of key functional groups is of fundamental importance. Aldehydes play an important role as synthetic precursors because they are easily obtained through the carbonylation reactions of hydrocarbons. 2] Despite the importance of amido compounds, there are relatively few practical methods available for their efficient and environmentally benign direct synthesis. Although the catalyzed oxidative amidation of aldehydes has been investigated for several decades, major challenges still remain, including: 1) undesired imine formation when primary amines are used in the reactions with aldehydes; 2) most of the currently used methods employ strongly oxidizing agents that lead to low chemoselectivities; and 3) these methods have limited functional-group tolerance. Few methods allow the conversion of aliphatic aldehydes and their corresponding amides are obtained in low-to-moderate yields. 6c, k, o, q] Only recently, Chan and co-workers reported a metal-promoted amidation reaction with iminoiodinanes that tolerated a broad range of aliphatic aldehydes. In a previous work, we reported that the Rh complex of the ligand bis(5-H-dibenzo[a,d]cyclohepten-5yl)-amine (trop2NH), complex 1, is an easily accessible and storable precursor complex of amido complex 2 upon the addition of base (Scheme 1). This latter complex is a highly efficient catalyst for hydrogenation reactions and, especially, for dehydrogenative coupling reactions (DHCs) in the presence of a hydrogen acceptor (A). In these reactions, a primary alcohol is coupled with either water, MeOH, or primary amines to afford carboxylic-acid derivatives. Computations have shown that these reactions proceed step-wise according to Equations (1) and (2).

Zero-Valent Amino-Olefin Cobalt Complexes as Catalysts for Oxygen Atom Transfer Reactions from Nitrous Oxide

The synthesis and characterization of several zero-valent cobalt complexes with a bis(olefin)-amino ligand is presented. Some of these complexes proved to be efficient catalysts for the selective oxidation of secondary and allylic phosphanes, as well as diphosphanes, even with a direct P-P bond. With 5 mol % catalyst loadings the oxidations proceed under mild conditions (25-70 °C, 7-22 h, 2 bar N2 O) and afford good to excellent yields (65-98 %). In this process, the greenhouse gas N2 O is catalytically converted into benign N2 and added-value organophosphorus compounds, some of which are difficult to obtain otherwise.

Homogeneously catalysed conversion of aqueous formaldehyde to H2 and carbonate

Small organic molecules provide a promising solution for the requirement to store large amounts of hydrogen in a future hydrogen-based energy system. Herein, we report that diolefin–ruthenium complexes containing the chemically and redox non-innocent ligand trop2dad catalyse the production of H2 from formaldehyde and water in the presence of a base. The process involves the catalytic conversion to carbonate salt using aqueous solutions and is the fastest reported for acceptorless formalin dehydrogenation to date. A mechanism supported by density functional theory calculations postulates protonation of a ruthenium hydride to form a low-valent active species, the reversible uptake of dihydrogen by the ligand and active participation of both the ligand and the metal in substrate activation and dihydrogen bond formation.

Determination of stability constants of ternary copper(II) complexes formed with picolinic acid and several amino acids

ABSTRACT In this work, the formation of ternary complexes with their respective formation constants in the systems formed by copper (II), picolinic acid and the amino acids = histidine (His), aspartic acid (HGly), proline (HPro), α-alanine (HαAla), β-alanine (HβAla), serine (HSer), threonine (HThr), phenylalanine (HPhe) and methionine (HMet)) was detected. The analysis involves the use of the potentiometric data with the least-squares program LETAGROP in aqueous solution at 25°C in 1M KNO3 solution. The relative stability of the ternary complexes was compared with the binary ones considering the values of Δlog K and log χ. Subsequently using the formation constants, the species distribution diagrams were generated and are briefly discussed here. The Cu (II)–picolinic acid–glutamic acid, Cu (II)–picolinic acid–serine and Cu (II)–picolinic acid–histidine systems were characterised by UV–Vis molecular absorption spectroscopy and cyclic voltammetry, obtaining results that confirm the formation of ternary complexes with octahedral geometry.