Discovery of a Novel Ring Fragmentation Reaction; Efficient Preparation of Tethered Aldehyde Ynoates and N-Containing Heterocycles;Radical Addition Approach to Asymmetric Amine Synthesis

摘要

This dissertation describes the development of a novel ring fragmentation reaction in which cyclic γ-silyloxy-β-hydroxy-α-diazoesters undergo efficient rupture of the Cβ−Cγ bond when treated with tin tetrachloride to provide tethered aldehyde ynoate products with varying tether length, in high yield. Tethered aldehyde ynoates are versatile intermediates and this functional group combination is unique to this fragmentation. The synthetic utility of tethered aldehyde ynoates is highlighted by their predisposition to undergo facile intramolecular [1,3]- dipolar cycloaddition reactions in presence of bistrimethylsylil-α-amino acids to provide 2,5-dihydropyroles. The ability to quickly assemble such structural motifs encouraged studies on the synthesis of steroidal alkaloid solanidine. A new method for the N-amination of oxazolidiones with NH2Cl was investigated and provides efficient access to acyl hydrazines. However, the full scope of the reaction has not been yet fully explored. The study of isopropyl radical additions to N-acylhydrazones and comparison of several stereocontrol elements on the oxazolidinone moiety revealed that all are effective.