Estudio de sistemas catalíticos basados en cobre para reacciones de transferencia de grupos carbeno y de adición radicalaria

Abstract

This Memoiy describes the use of copper(I) and copper(II) complexes as efficient catalysts for the carbene transfer and radical addition reactions. The Thesis is divided into three Chapters. The first one is concerned with the detection and characterization of copper-carbene and copper-diazo adducts as intermediates in carbene transfer reactions from diazocompounds using the complex TpMsCu(THF) as catalytic precursor. Besides, the data obtained from the kinetic studies of the carbene insertion reaction into O-H bond of water by the measurement of the evolution of dinitrogen have allowed us to make a mechanistic proposal. The second Chapter is focused on the epoxidation of aldehydes with diazocompounds via sulfur ylide catalyzed by TpxCuL complexes. The presence of an organic sulfide as co-catalyst generates a sulfur ylide from diazocompound. Finally, the third Chapter has two parts: i) the study of the catalytic capabilities of several Cu(I) complexes bearing strong electron donor tripodal N-heterocyclic carbene ligands in ATRA reactions; ii) the synthesis of 2- azabicyclo[3.3.1]nonanes using different trichloroacetamides as starting materials by copper-catalyzed ATRC reactions. These later results have been obtained during a collaboration with Prof. Bonjoch from Universidad de Barcelona, which has afforded the starting materials. Chapter I. Detection of Copper-Carbene Intermediates in the Eunctionalization of X-H Bonds using TpxCuL Complexes as Catalysts. During the last two decades, our research group lias reported the catalytic capabilities of Cu(I) complexes bearing hydrotrispyrazolylborate ligands, TpxCuL, in carbene transfer reactions from diazocompounds such as the addition to double and triple bonds or X-H insertion. In spite of the wide number of catalytic systems studied, none copper-carbene intermediate was ever detected or isolated in the reaction mixtures. In the work herein presented, the reaction of the corresponding copper complex TpxCuL and ethyl 2- phenyldiazoacetate (PhEDA) has allowed to detect several copper-diazo adducts of composition TpxCu[r]1- N2C(Ph)(C02Et)] and copper-carbene intermediates, TpxCu=C(Ph)(C02Et). Interestingly, a good correlation between the values of v(CO) of the TpxCu(CO) complexes and the chemical shift of the carbenic carbon in TpxCu=13C(Ph)(C02Et) has been found. These intermediates represent the first examples of Cu(I)-carbene of this type bearing tricoordinated ligands with a tetrahedral geometiy around the metal center. With the aim of gaining further information about the different steps in the catalytic cycle, we have carried out kinetic studies based on the measurement of the evolution of dinitrogen during the carbene insertion reaction into O-H bond of H20 catalyzed by the complex TpMsCu(THF). These studies have shown that the copper-diazo adduct TpMsCu[ri1-N2C(Ph)(C02Et)] constitutes a dormant species in this system, beg the reservoir of the available copper species in solution. A mechanistic proposal has been made for this transformation on the basis of the collected data. Chapter II. Epoxidation of Aldehydes via Sulfur Ylides Catalyzed by Tp'CuL Complexes. This Chapter describes the catalytic capabilities of several TpxCuL complexes in the reaction of phenyldiazomethane and aldehydes to form epoxides via sulfur ylide. The complex TpDr3Cu(NCMe) showed the highest activity under mild conditions and in remarkable short reaction times. The capability of the complex TpMsCu to form stable adducts has allowed the characterization of several copper-sulfide adducts of composition TpMsCu(SR2). Finally, the in situ generation of the diazo reagent from benzaldehyde tosylhydrazone salt has led to the conversion of benzaldehyde into stilbene oxide in very high yields, exceeding the results reported with Cu(acac)2 and similar to those with Rh2(OAc)4. Chapter III. Copper-catalyzed ATRA and ATRC Reactions. Copper-based catalytic systems with strong electron-donating multidentate nitrogen-based ligands have proven to be very efficient in ATRA reactions. With these precedents in mind, we decided to test in ATRA reactions other kind of Cu(I) complexes, containing polidentante N-heterocyclic carbene ligands. Complex [TIMENtBuCu](PF6)J showed a high catalytic activity in the ATRA reaction of 1-hexene with CCI4 in the presence of AIBN as reducing agent. On the other hand, we have carried out the synthesis of 2-azabicyclo[3.3.1]nonanes using different trichloroacetainides as starting material by copper-catalyzed ATRC reactions. Thus, high yields were obtained in the ATRC reactions of activated trichloroacetainides catalyzed by Tp/üuCu(NCMe) and TpiBuCuCl complexes. However, these catalysts provided poor results when non-activated trichloroacetamides were used. Therefore, we decided to employ [(TPMA)CuCl] and [(TPMA)CuCl]Cl complexes as catalysts for this kind of substrates, with significant yields enhancements. Indeed, our results have improved significantly those reported by Bonjoch and co-workers using BU3S11H and AIBN, avoiding the disadvantages of these compounds such us then high neurotoxicity, high cost and purification problems.