RhI/RhIII catalyst-controlled divergent aryl/heteroaryl C-H bond functionalization of picolinamides with alkynes

The ability to establish switchable site-selectivity through catalyst control in the direct functionalization of molecules that contain distinct C-H bonds remains a demanding challenge that would enable the construction of diverse scaffolds from the same starting materials. Herein we describe the realization of this goal, namely a divergent heteroaryl/aryl C-H functionalization of aromatic picolinamide derivatives, targeting two distinct C-H sites, either at the pyridine ring or at the arene unit, to afford isoquinoline or ortho-olefinated benzylamine (or phenethylamine) derivatives. This complementary reactivity has been achieved on the basis of a RhIII/RhI switch in the catalyst, resulting in different mechanistic outcomes. Notably, a series of experimental and DFT mechanistic studies revealed important insights about the mechanism of the reaction and reasons behind the divergent regiochemical outcomeWe thank the Spanish Government (MINECO, CTQ2012-35790) for financial support. N. R. thanks the MICINN for a Ramón y Cajal contract and the European Commission for a Marie Curie Career Integration Grant (CIG: CHAAS-304085). We also thank the Centro de Computación Científica de la UAM for their generous allocation of computer tim

Minimizing the entropy penalty for ligand binding: lessons from the molecular recognition of the histo blood-group antigens by human galectin-3

6 p.-5 fig.-2 tab.Ligand conformational entropy plays an important role in carbohydrate recognition events. Glycans are characterized by intrinsic flexibility around the glycosidic linkages, thus in most cases, loss of conformational entropy of the sugar upon complex formation strongly affects the entropy of the binding process. By employing a multidisciplinary approach combining structural, conformational, binding energy, and kinetic information, we investigated the role of conformational entropy in the recognition of the histo blood‐group antigens A and B by human galectin‐3, a lectin of biomedical interest. We show that these rigid natural antigens are pre‐organized ligands for hGal‐3, and that restriction of the conformational flexibility by the branched fucose (Fuc) residue modulates the thermodynamics and kinetics of the binding process. These results highlight the importance of glycan flexibility and provide inspiration for the design of high‐affinity ligands as antagonists for lectins.We thank Agencia Estatal de Investigacion and ISCIII of Spain and the European Research Council for financial support.Peer reviewe

Catálisis homogénea con oro: desde los primeros pasos hasta la fiebre del oro

Gold has been a latecomer in organic synthesis, mainly because of the wrong perception of its lack of reactivity in homogeneous catalysis. Here, we present a brief account of the key discoveries that have fi nally led to a true gold rush in the last ten years.El oro ha tardado en incorporarse a la síntesis orgánica, principalmente debido a la errónea percepción de su falta de reactividad en catálisis homogénea. Aquí presentamos un breve relato de los descubrimientos clave que han desencadenado una auténtica “fi ebre del oro” en los últimos diez años

Synthesis of (-)-Cannabimovone and Structural Reassignment of Anhydrocannabimovone through Gold(I)-Catalyzed Cycloisomerization

The first total synthesis of cannabimovone from Cannabis sativa and anhydrocannabimovone was achieved by means of a highly stereoselective gold(I)‐catalyzed cycloisomerization. The results led to reassignment of the structure of anhydrocannabimovone

Gold(I)-Catalyzed Inter- and Intramolecular Additions of Carbonyl Compounds to Allenenes

The gold(I)-catalyzed intramolecular reaction of allenes with oxoalkenes leads to bicyclo[6.3.0]undecane ring systems, although in the case of terminally disubstituted allenes, seven-membered rings are formed. The related intermolecular addition of aldehydes to allenenes also gives seven-membered rings

Ni-Catalyzed Borylation of Aryl Fluorides via C–F Cleavage

A Ni-catalyzed borylation via C–F activation is described. This protocol is distinguished by a wide scope, including unactivated fluoroarenes, without compromising its efficiency and scalability, thus representing a significant step-forward toward the implementation of C–F activation protocols

Reactions of cationic hydrido complexes [Ru(CO)H(MeCN)2(PPh3)2]A (A ClO4, PF6) with alkynes. The crystal structure of [Ru(CO) (MeOOCCCHCOOMe) (MeCN)2(PPh3)2]ClO4

Reactions of [Ru(CO)H(MeCN)2(PPh3)2]A with mono- and di-substituted acetylenes give the alkenyl derivatives [Ru(CO)(RCCHR′)(MeCN)2(PPh3)2]A (A ClO4, R H; R′ C3H7, CMe3, Ph, COOMe; R R′ COOMe; A PF6, R R′ Ph) resulting from a cis-insertion of the alkyne into the RuH bond. The reaction of the perchlorate complex with diphenylacetylene yields alkenyl chlororuthenium derivatives resulting from the unexpected reduction of the perchlorate anion to chloride. The crystal structure of [Ru(CO)(MeOOCCCHCOOMe)(MeCN)2(PPh3)2]ClO4 has been determined by X-ray crystallography (orthorhombic, P212121, a 14.498(1), b 15.080(1), c 22.677(2) Å). In this cationic complex both phosphine and acetonitrile molecules and, consequently, the carbonyl and alkenyl ligands are mutually trans, whereas in the other complexes only the phosphine ligands are in trans disposition, as inferred from 1H NMR spectroscopic data. © 1989.We gratefully acknowledge financial support of this work by the DGICYT (PB 020102) and the CSICPeer Reviewe