Antonio Suárez

Bio: Antonio Suárez is an academic researcher from University of A Coruña. The author has contributed to research in topics: Diphosphines & Palladium. The author has an hindex of 20, co-authored 41 publications receiving 868 citations. Previous affiliations of Antonio Suárez include University of Santiago, Chile & University of Santiago de Compostela.

Formation, characterization, and structural studies of novel thiosemicarbazone palladium(II) complexes. Crystal structures of [{Pd[C6H4C(Et)NNC(S)NH2]}4], [Pd{C6H4C(Et)NN C(S)NH2}(PMePh2)] and [{Pd[C6H4C(Et)NNC(S)NH2]}2(µ-Ph2PCH2PPh2)]

Abstract: The reaction of thiosemicarbazones 4-MeC6H4C(Me)NN(H)C(S)NH2 a, C6H5C(Et)NN(H)C(S)NH2 b and 4-MeC6H4C(Me)NN(H)C(S)NHMe c with K2[PdCl4] led to tetranuclear palladium(II) compounds, [{Pd[4-MeC6H3C(Me)NNC(S)NH2]}4], 1a, [{Pd[C6H4C(Et)NNC(S)NH2]}4] 1b, and [{Pd[4-MeC6H3C(Me) NNC(S)NHMe]}4] 1c; the ligands are tridentate through the [C, N, S] atoms and they are deprotonated at the NH group. The Pd–Schelating bond is sufficiently strong for the complexes to undergo reactions with nucleophiles without bond cleavage. The molecular structure of 1b has been determined by single-crystal diffraction, confirming the formation of the tetranuclear moieties. Hydrogen bonding N· · ·H and S· · ·H links Pd4 clusters into strands in the solid state. Reaction of 1a and 1b with phosphines gave mono- and di-nuclear species, 2a, 2b, 3b and 5a, 5b, respectively. Treatment with 1,1′-bis(diphenylphosphino)ferrocene led to trimetallic compounds 6a and 6b. The molecular structure of 3b has been determined by X-ray crystallography; dimer units are present through N· · ·H hydrogen bonds. The reaction of 2b with hydrochloric acid resulted in a 1∶1 electrolyte, 4b, with NH and CS groups. Alternatively, treatment of 1a, 1b and 1c with strong chelating phosphines produced mononuclear compounds with only cleavage of the Pd–Sbridging bonds, 7a, 7b, 7c and 8c with the diphosphine monodentate; 7a and 7b were obtained with the dinuclear species 7a′ and 7b′, respectively, as impurities, where the bidentate phosphine ligand bridges two metallated units. The crystal structure of one such compound, 7b′, with a bridging bis(diphenylphosphino)methane ligand, is also described.

Catalytic direct arylation with aryl chlorides, bromides, and iodides: intramolecular studies leading to new intermolecular reactions.

Abstract: A catalyst for the intramolecular direct arylation of a broad range of simple and heterocyclic arenes with aryl iodides, bromides, and chlorides has been developed. These reactions occur in excellent yield and are highly selective. Studies with aryl iodides substrates revealed that catalyst poisoning occurs due to the accumulation of iodide in the reaction media. This can be overcome by the addition of silver salts which also permits these reactions to occur at lower temperature. The utility of the methodology is illustrated by a rapid synthesis of a carbazole natural product and by the synthesis of sterically encumbered tetra-ortho-substituted biaryls via ring-opening reactions of the direct arylation products. Mechanistic investigations have provided insight into the catalyst's mode of action and show the presence of a kinetically significant C-H bond cleavage in palladium-catalyzed direct arylation of simple arenes. Knowledge garnered from these studies has led to the development of new intermolecular arylation reactions with previously inaccessible arenes, opening the door for the development of other new direct arylation processes.

Manganese-Catalyzed C–H Activation

Abstract: Manganese is found in the active center of numerous enzymes that operate by an outer-sphere homolytic C–H cleavage. Thus, a plethora of bioinspired radical-based C–H functionalizations by manganese catalysis have been devised during the past decades. In contrast, organometallic C–H activation by means of manganese catalysis has emerged only recently as an increasingly viable tool in organic synthesis. These manganese(I)-catalyzed processes enabled a variety of C–H functionalizations with ample scope, which very recently set the stage for substitutive C–H functionalizations. The versatile manganese catalysis largely operates by an isohypsic, thus redox-neutral, mode of action through chelation assistance, and provided step-economical access to structurally divers compounds of relevance to inter alia bioorganic, agrochemical, and medicinal chemistry as well as the material sciences.

Palladium-Catalyzed Arylation of Azole Compounds with Aryl Halides in the Presence of Alkali Metal Carbonates and the Use of Copper Iodide in the Reaction

Abstract: The reactions of iodobenzene with azole compounds, 1,2-disubstituted imidazoles and 2-substituted oxazoles and thiazoles, were examined in the presence of catalytic amounts of Pd(OAc)2 and PPh3 in DMF using alkali metal carbonates as bases. It was found that the coupling products, 5-arylazoles, could be selectively produced in good yields by using Cs2CO3. In the case that their 2-position is unsubstituted, the site could also be arylated. In reactions using bromobenzene in place of iodobenzene, K2CO3 was also as effective as Cs2CO3. The addition of a stoichiometric amount of CuI appeared to specifically promote the reactions of thiazoles as well as those of thiophene derivatives. The reactions of 2-unsubstituted azole compounds with aryl iodides could be mediated by CuI to some extent without using the palladium species to give 2-arylazoles.