C-c and c-n couplings promoted by transition metalsschiff condensations and aldol reactions

Resumen

This doctoral thesis is presented as a compilation of scientific articles, some of which have been published or are under revision in high impact international journals. The core of the thesis is the preparation of new complexes, principally paramagnetic complexes, with the ligand 2-pyridinecarboxaldehyde, which is also known as pyca. Simple, commercially available, and low-cost simple salts are used as the substrates. The electronic properties and structures of these complexes, as well as their behavior in solution and in the solid state, are explored using spectroscopic and analytical techniques, including magnetism, UV-vis absorption, single-crystal and powder X-ray diffraction, relaxivity (for evaluation of their potential as possible contrast agents in magnetic resonance imaging), etc. The chapters and sub-sections of the thesis are listed below, and a summary of the most relevant content is provided. Chapter 2, INTRODUCTION, provides the context for and a brief description of the previous publications of the research group, and is organized into three main themes: complexes with the 2-pyridinecarboxaldehyde ligand (Reactivity I), aldol addition (Reactivity II), and paramagnetic complexes. Chapter 3, OBJECTIVES, presents the principal aims that were established from these initial themes. However, it should be noted that other specific objectives were established during the execution of the thesis. The experimental methodology, as well as the techniques used to characterize new species, is presented in Chapter 4, METHODOLOGY. Chapter 5, RESULTS AND DISCUSSION, describes in detail the work and progress towards the objectives in Chapter 3. Studies based on the first two themes of the introduction (Reactivity I and II) constitute the main topic of this thesis, the reactivity of complexes of the pyca ligand with various metallic fragments. Studies related to these themes are detailed in Sections 5.1-5.4. Additional specific objectives (Reactivity III and IV), such as the formation of hydrates and the synthesis of new complexes of Cu(I) with isocyanides, are discussed in Sections 5.5 and 5.6 of this chapter. The theme of paramagnetic complexes is included in these sections rather than being discussed separately. Chapter 6 shows the principal CONCLUSIONS of this thesis. Chapter 7, PUBLISHED (or submitted) ARTICLES, consists of the publications that resulted from the results in Chapter 5. Article I reports the preparation of Mn(II) complexes containing a ligand formed by the condensation of two molecules of 2-pyridinecarboxaldehyde, known as Indz, and other similar ligands prepared using various commercial pyridinealdehydes. Article II explores the coordination of the ligand Indz (also known as Py-Indz) to other metallic fragments of transition elements or main-group metals; 17 new structures in which this species is incorporated as a chelate with properties similar to the classic ligand 2,2ʹ-bipyridine were obtained. Article III explores the synthesis and structural versatility of the iminopyridine formed from the pyca ligand and β-alanine in the coordination sphere of Cu(II). The new complexes are evaluated as possible contrast agents, and their cytotoxicity in various cell lines is assessed. The study of aldol addition induced by Cu(II) complexes is the subject of Article IV; the results include an example of a stereoselective double aldol addition. Experimental procedures for results that are described in Chapter 5, but not included in any of the articles contained in Chapter 7, are compiled in Chapter 8, ANNEXES (subsection 8.1). Other articles, end of course projects, and Masters’ theses in which I collaborated during my doctoral studies are presented in Section 8.2. The bibliographical references are included at the bottom of the pages and also in the final chapter 9 BIBLIOGRAPHY for the reader's convenience. In addition, each article or manuscript carries its specific and independent bibliographic references.