Ring-opening-ring-closing metathesis of bicyclo[2.2.2]octenes: A novel synthesis of decalins and hydrindanes, and, Studies of the scope and source of selectivity of a chemo- and diastereoselective elimination reaction .

摘要

This dissertation presents two methodology studies and a mechanistic investigation. First, the use of the Grubbs ruthenium catalysts is described to effect a tandem ring-opening - ring-closing metathesis reaction (ROM/RCM), where a strained bicyclic system is treated with a transition metal catalyst to give either a hydrindane or decalin ring system. Second, a methodology study is presented which builds upon the known diastereoselective aldol reaction of boron enolates of certain beta-alkoxy methyl ketones with aldehydes to provide beta,beta'-monoprotected dihydroxy ketones with synthetically useful anti diastereoselectivities. The beta-alkoxy group in these aldol adducts can be eliminated in preference to the beta-hydroxy group by treatment with catalytic amounts of potassium carbonate in aqueous alcoholic solvent. The scope of this reaction is demonstrated by application to a variety of substrates containing alkyl and aromatic side chains, varying steric demand, and different leaving groups. This method is also general for the construction of tri-substituted olefins. Finally, studies of the source of the reaction's chemoselectivity are presented which focus on the relative rates of three processes involved in the reaction: proton exchange at each of the alpha carbons and leaving group ejection.