Thies Thiemann

By Fatima Merza, Ahmed Taha and Thies Thiemann

The Wittig olefination utilizing phosphoranes and the related Horner-Wadsworth-Emmons (HWE) reaction using phosphonates transform aldehydes and ketones into substituted alkenes. Because of the versatility of the reactions and the compatibility of many functional groups towards the transformations, both Wittig olefination and HWE reactions are a mainstay in the arsenal of organic synthesis. Here, an overview is given on Wittig- and Horner-Wadsworth-Emmons (HWE) reactions run in combination with other transformations in one-pot procedures. The focus lies on one-pot oxidation Wittig/HWE protocols, Wittig/HWE olefinations run in concert with metal catalyzed cross-coupling reactions, Domino Wittig/HWE—cycloaddition and Wittig-Michael transformations.

Part of the book: Alkenes

By Thies Thiemann

Thiophene S-oxides constitute a class of molecules that have been studied in more detail only recently. Their existence as intermediates in the peracid mediated oxidation of thiophenes to thiophene S,S-dioxides, however, has been known over some time. Over the last 20 years, a larger number of thiophene S-oxides have been prepared and isolated in pure form. Thiophene S-oxides have been found to be good dienes in [4 + 2]-cycloaddition reactions, where they react with electron-poor, electron-neutral and electron-rich dienophiles with high syn π-facial stereoselectivity. Thiophene S-oxides have been found to be metabolites of thienyl-containing pharmaceuticals such as the anti-platelet drugs ticlopidine and clopidogrel. The chapter gives an overview of the preparation and reactivity of this class of compounds.

Part of the book: Chalcogen Chemistry