Studies toward Augmented Carbene/Alkyne Cascade Reactions and Ruthenium Catalysts for Propargylic Substition
This thesis presents three main projects. The first project presents synthetic strategies toward augmented cascade reactions. The second part discusses the synthesis of a ruthenium catalyst and its application for propargylic substitution. The third part describes an improvement of a Robinson annulation for the synthesis of aplykurodinone 1. Alkyne/cascade reactions are highly effective processes in organic chemistry, and they can provide complex molecules in a single synthetic method. Our approach is based on a rhodium-catalyzed diazo-decomposition of readily available starting materials. Then the reaction goes through metal-carbene and alkyne insertion, and finally C-H insertion or alkyl migration. Because of ring-strain and steric effects, a cyclic syn-alkynyl diazoacetate approach underwent direct C-H insertion. A linear di-alkynyl diazoacetate approach underwent a gold-catalyzed cascade reaction to generate a polycyclic product. Substituted alkynes are widely used for organic polymers and pharmaceuticals. Furthermore, propargylic substitution is an important transformation of substituted alkynes. Based on reported metal-catalyzed propargylic substitutions, we designed and synthesized various ruthenium tris(pyrazoly)borate complexes to test propargylation. When studying ruthenium-catalyzed reactions, we discovered that the inorganic salt (NaPF6) has catalytic activities toward propargylic substitution. Aplykurodinone 1 was isolated from the skin of sea slugs belonging to the Aplysiidea family and might be part of the animals defense mechanism. We developed a synthetic route toward aplykurodinone 1. A challenging transformation in our synthetic route used a Robinson annulation to form the bicyclic core struture of aplykurodinone 1. We modified the Robinson annulation to perform this reaction consistently and efficiently.