Efforts towards the total synthesis of vinigrol, stereoselective synthesis of carbocycles and gold-catalyzed benzannulation

The Diels-Alder reaction is a very useful tool for the art and science of total synthesis. This thesis describes the exploitation of this reaction in the context of the synthesis of two different natural products, a diterpene and a steroid. A new approach to the total synthesis of vinigrol relied on an intramolecular Diels-Alder reaction to generate two of three rings of the carbocyclic skeleton in one step. Initially, it was possible to prove that the intramolecular cycloaddition could effectively form the desired six and eight-membered ring with the right regiochemistry. Then, the starting materials were modified in order to accommodate the necessary functionality needed for the total synthesis. As a result, a functionalized tricyclic core of vinigrol was synthesized. A second-generation synthesis of a functionalized core was established taking advantage of a diastereoselective ketal Claisen rearrangement. The functionalization of the C8-C8a was studied as well as the synthesis of the allylic diol of the B ring. The Diels-Alder reaction was also examined in the context of domino reactions. Optimization of the oxy-Cope/Claisen/ene/hydroxy-directed Diels-Alder reaction was achieved. It was also possible to study this reaction in order to accommodate cis precursors and apply it to the synthesis of digitoxigenin, a 14beta-hydroxy steroid. Many approaches were investigated to synthesize a functionalized cis precursor designed for the total synthesis. The rearrangement of a functionalized cis-precursor is also discussed. During the studies aimed at the application of the oxy-Cope/Claisen/ene/hydroxy-directed Diels-Alder reaction, a novel gold-catalyzed benzannulation reaction was discovered. Treating 3-hydroxy-1,5-enynes with a cationic gold catalyst led to tetrahydronaphthalenes in good yield. The scope and limitations of this methodology was examined. During this research, a new Au(PPh3)Cl and acid catalyst system was detected