Reacciones de formación de sistemas policíclicos: I. Síntesis de taxoesteroides mediante metátesis de dieninos. II. Estudios teóricos de reacciones de ciclación de metátesis y reacciones de cicloadición [3+2] catalizadas por Pd

Abstract

Polycyclic systems containing medium size rings are present in a high number of compounds and constitute the basic skeleton of natural and non natural products of great importance. The construction of these systems continues being a challenge in the Synthetic Organic Chemistry. Transition metals have become ideal candidates for their synthesis, because of their multiple advantages: all functional groups can coordinate to some transition metals, and after that, the reactivity of this functional group is incredibly changed very often. Besides, most of the reactions can be carried out in a very specifically way, and it is possible to distinguish between similar positions into the same molecule. Another advantage is that transition metals can participate in domino or tandem reactions, where more than one bond can be formed at the same time. However, the mechanisms of these transformations are often complicated and difficult to understand. This fact, more than a disadvantage can be considered a great chance for the development of new chemical transformations. This memory describes the results obtained from the investigation of two important reactions catalyzed by a transition metal: metathesis and cycloaddition reactions. Both transformations constitute big synthetic tools and allow achieving a big molecular complexity in only one step; this is why they are so useful in the construction of polycyclic systems.