Synthesis and reactions of a-oxo sulfines and 3,6-dihydro-2H-thiopyran s-oxides

Abstract

The primary objective of the research described in this thesis is to extend the fundamental knowledge about the chemistry of a-oxo sulfines and 3,6-dihydro-2H-thiopyran S-oxides derived therefrom. First, a general overview is given about the most important features of sulfines (Chapter 1).Chapter 2 focuses on the synthesis of a-oxo sulfines. First, a literature overview of synthetic methods leading to this special class of sulfines is given. Next, the scope of the method for the in situ synthesis of a-oxo sulfines as developed in Nijmegen was extended further. The results of this research are described in Section 2.2. In the final Section, it will be shown that a modification of the experimental procedures allows the actual isolation of a wide range of differently substituted a-oxo sulfines as such. The isolation of a-oxo sulfines gives the opportunity to study the chemical behavior of these compounds in more detail. Some reactions involving a-oxo sulfines are described in Chapter 3. Special attention is given to the Diels-Alder reaction of a-oxo sulfines with several achiral (Chapter 3) and chiral dienes (Chapter 4) leading to functionalized 3,6-dihydro-2H-thiopyran S-oxides. As a spin-off a newly developed synthetic procedure for the synthesis of chiral 1-acyloxy-1,3-butadienes will be presented. In this context, the synthesis of a new class of chiral dienes derived from a-amino acids will also receive attention.Chapters 5 and 6 are devoted to the synthetic utility of 3,6-dihydro-2H-thiopyran S-oxides derived from a-oxo sulfines. In Chapter 5 the potential of functionalized 3,6-dihydro-2H-thiopyrans (obtained by deoxygenation of their corresponding S-oxides) as substrates in [3,3]- and [2,3]-sigmatropic rearrangement reactions will be described. Chapter 6 deals with preliminary attempts toward the synthesis of thiosugar analogs, using 3,6-dihydro-2H-thiopyrans as the starting material.