Stereoselective transformations using chiral hypervalent iodine reagents

• Main Author: Malmedy, Florence
• Published: Cardiff University 2016
• Subjects: 547; QD Chemistry
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.690941

Hypervalent iodine (III) compounds are efficient, selective and environmentally friendly reagents. Due to their electrophilic nature and excellent leaving group ability, they can be used to mediate oxidative transformations; for example, the oxidation of sulfides to sulfoxides, the α-functionalisation of ketones, the dearomatisation of phenols, the functionalisation of alkenes and, more recently, the rearrangement of various substrates. In this thesis, the stereoselective rearrangement of propiophenone derivatives mediated by chiral hypervalent iodine reagents is described (Scheme i). A chiral lactate-based iodine (III) reagent was used to synthesise 2-arylpropionate derivatives with moderate to good yields and enantioselectivities. These compounds are highly attractive as they are direct precursors to Non-Steroidal Anti Inflammatory Drugs (NSAIDs). Scheme i. Rearrangement of propiophenone derivatives to 2-aryl-propionates. The cyclisation of malonate derivatives, mediated by hypervalent iodine reagents has also been investigated (Scheme ii). Several lactone derivatives were synthesised with this method, achieving moderate to good yields. Scheme ii. Cyclisation of malonate derivatives to synthesise functionalised lactones. Finally, the design of a new hypervalent iodine reagent is described (Figure i). After its synthesis, the pyridine-based reagent was tested in several model reactions, usually mediated by iodine (III) reagents. Its reactivity was similar to the one of other hypervalent iodine reagents. However, its ability to induce stereoselectivity to different products was quite poor. Figure i. Structure of the new hypervalent iodine reagent.