Syntheses Of Bridged-and Spiro-Cyclic Compounds Via Tandem Reaction

This thesis is focused on the development of synthetic methodologies towards bridged-, spiro-and fused-ring conpounds, which are of potential pharmacal activity or synthetic application value.In chapter1, based on the types of reactions and the product structures, recent literature reports related to the topic of this thesis were summarized.In chapter2, the transformation of1,6-enyne into the bridged bicyclic systems has been first accomplished by copper(I)-catalyzed tandem cycloadition reaction. The reaction provides a straightforward approach for the synthesis of structurally diverse, strained and bridged-bicycles in good yields with moderate to excellent diastereoselectivity.In chapter3, a novel, organocatalytic, asymmetric, one-pot protocol for the preparation of chiral tri-oxygenated spirocycloalkanediones with up to99%ee has been explored. This procedure features high stereoselectivity, introduction of tri-oxygenated functional groups and the efficient construction of at least two chiral centers, with one of these being all-carbon quaternary.In chapter4, a highly chemoselective one-pot reaction has been developed involving a tandem semipinacol rearrangement/oxa-Michael addition sequence in which the in situ generated ketol diene intermediate can be transformed specifically to either the spiro-or fused-dihydrofuran products depending upon the acid used. This one-pot tandem reaction represents a general synthetic methodology for the syntheses of the two different kinds of furan derivatives.The research strategies in the thesis will provide some useful methods for the synthesis of natural product and enrich the content of organic chemistry.