Approaches towards the stereoselective sulfonium ylide [3,3]-sigmatropic rearrangement

Sulfonium ylides are formed using mild conditions and a diazo decomposition reaction catalyzed by a transition metal. These intermediates can undergo a variety of synthetically useful transformations such as [1,2]-insertions and [2,3]-sigmatropic rearrangement. We have recently discovered a novel sulfonium ylide [3,3]-sigmatropic rearrangement to highly substituted indolines. This dissertation describes our studies on the scope and stereoselectivity of the rearrangement.;A variety of chiral rhodium (II) catalysts were utilized in the reaction and the composition of the rearranged products were analyzed by chiral HPLC. The collected data provided us with important information about the influence of catalyst structure on the enantioselectivity of sulfonium ylide [3.3]-sigmatropic rearrangements. In the course of this investigation we observed a minor difference in diastereoselectivity among various catalysts. Further studies led us to propose that the reaction preceded via a metal associated ylide intermediate. This theory was supported when we observed a complete loss in diastereoselectivity when various Lewis bases were introduced into the reaction media. This is the first indication that a transition metal is present at the product determining step in sulfonium ylide rearrangements.The scope of sulfonium ylide [3,3]-sigmatropic rearrangement was expanded to include imidazole derivatives. The rearranged imidazolines were proposed to have high synthetic interest. Various vinyldiazophosphonates were synthesized and used in the rearrangement. The products were isolated in good yields and with high diastereoselectivity. An attempted transformation of the rearranged thioindoline by using Michael addition resulted in isolation of unexpected products.