General Papers ARKIVOC 2015 (v) 34-43 Page 34 © ARKAT-USA, Inc Palladium-catalyzed coupling reactions for the preparation of concatenated azoles Delia Hernández,* a C. Giovana Granados, b Esmeralda Sánchez, a Fernando Albericio, c,d and Mercedes Álvarez* ,c,e a Química Orgánica y Biotecnología, Facultad de Ciencias Químicas, Universidad Veracruzana, Orizaba, Veracruz, México b Unidad de Diseño y Síntesis de Biomoléculas, Departamento de Química, Centro de Investigación y de Estudios Avanzados (CINVESTAV-IPN), México, D.F. c Institute for Research in Biomedicine, Barcelona Science Park-University of Barcelona, Baldiri Reixac 10, 08028 Barcelona, Spain d Department of Organic Chemistry, University of Barcelona, 08028 Barcelona, Spain e Laboratory of Organic Chemistry, Faculty of Pharmacy, University of Barcelona, 08028 Barcelona, Spain E-mail: mercedes.alvarez@irbbarcelona.org DOI: http://dx.doi.org/10.3998/ark.5550190.p009.017 Abstract The coupling reactions mediated by sp 2 -sp 2 transition metals, mostly Pd, allowed the chemoselective preparation of some synthetic compounds and intermediate structures of great complexity. This work describes the methodology used to obtain several derivatives with bisoxazole and thiazole-oxazole units. The required organozinc reagents were prepared from n- BuLi and ZnCl 2 , and the bimetallic derivative of ethyl oxazole-4-carboxylate was obtained by a second transmetalation with CuI. Keywords: Organometallic, oxazole, thiazole, transmetalation, coupling reactions Introduction In recent decades, some marine natural products have been found to be an important source of new bioactive compounds and drug leads. The chemical structures of marine products with heterocycles, such as 2,4´-bisoxazole, trisoxazole and 2,4´-thiazole-oxazole, substituted in different positions of the ring are common in different families of natural products (Figure 1).