Copper clusters as novel photocatalysts for aerobic oxidation of arylboronic acids and esters under ecofriendly conditions

CASTRO-GODOY, WILLBER D.; GIORDANO LAUREANO; SCHMIDT LUCIANA C.; BUCETA DAVID; LÓPEZ-QUINTELA ARTURO; ARGÜELLO, JUAN E

Carlos Paz

Encuentro; XIII Encuentro Latinoamericano de Fotoquímica y Fotobiología; 2017

Metal clusters can be defined as metal atom aggregates with sizes between 1 to 2 nm.[1] For these novel materials high chemical stability and novel properties including surprising high catalytic performances have been described.[2] Up to now, copper clusters (CuCLs) have attracted less attention than gold and silver clusters. However, due to their low cost and unique optical and catalytic properties different publications have recently reported the synthesis and characterization of CuCLs.[3] Besides, previous reports have demonstrated that photocatalytic behavior of CuCLs would be similar to the accepted one for photoactive semiconductors (SCs),[4] which involves the generation of reactive oxygen species, such as O2?-, HOO? or HO?, produced by the reaction between adsorbed water, molecular oxygen and photoelectrons when they migrate to the semiconductor´s surface. Recently, we have described the use of water soluble quantum dots for the oxidation of arylboronic acids and esters to obtain their corresponding phenols. In this investigation, the visible light photogenerated superoxide anion promotes the ipso hydroxylation of different arylboronic acids and esters.[5] Herein, we report for the first time the photocatalytic oxidation of different arylboronic acids and arylboronic esters using CuCLs under UV-A irradiation. The CuCLs were synthesized and characterized for López-Quintela group (Nanomag Laboratory, Research Technological Institute, University of Santiago de Compostela, Spain). Under optimized conditions; we further studied the reactivity scope of the reaction. This methodology proved to be compatible with electron donors and electron withdrawing substituents and the corresponding phenols from arylboronic esters were also obtained in good yields (48?87 %). On the other hand, arylboronic acids rendered phenols in very good to excellent yields (92?100%). [1] J. Calvo, J. Rivas, M. A. López-Quintela, in Encyclopedia of Nanotechnology, (Ed: Bharat Bhushan), Springer Verlag, Dordrecht, The Netherlands 2012, p 2639. [2] a) Y. Zhu, H. Qian, B. A. Drake, R. Jin, Angew. Chem. Int. Ed. 2010, 49, 1295; b) N. Vilar-Vidal, J. Rivas, and M. A. Lopez-Quintela, ACS Catal. 2012, 2, 1693. c) A. Corma, P. Concepción, M. Boronat, M. Sabater, J. Navas, M.Yacamán, E. Larlos, A. Posadas, M. López-Quintela, D. Buceta, E. Mendoza, G. Gullera, A. Mayoral, Nat. Chem. 2013, 5, 775. [3] a) C. Vázquez-Vázquez, M. Bañobre-López, A. Mitra, M. A. López-Quintela, J. Rivas, Langmuir 2009, 25, 8208; b) N. Vilar-Vidal, M. C. Blanco, M. A. López-Quintela, J. Rivas, C. Serra, J. Phys. Chem. C 2010, 114, 15924; c) N. Goswami, A. Giri, M. S. Bootharaju, P. L. Xabier, T. Pradeep, S. K. Pal, Anal. Chem. 2011, 83, 9676. [4] N. Vilar-Vidal, J. Rivas Rey, and M. Arturo López-Quintela, Small 2014, 10, 3632. [5] W. Castro-Godoy, L. Schmidt, D. Flores-Oñas, J. Pérez-Prieto, A. Peñéñory, R. Galian, J. Argüello. XX-SINAQO, Mar del Plata, Argentina. Noviembre 2015