Carbene-Catalyzed Reactions with Vinyl Sulfones

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DESCRIPTION (provided by applicant): The development of new chemical methodology is an important endeavor in the ability to access different privileged and bioactive molecules from natural products to therapeutic drugs. In particular, small molecule catalysis has undergone a powerful renaissance over the last decade leading to an explosion of efficient and stereoselective strategies for organic synthesis, providing a less toxic alternative and often biomimetic way to synthesize organic molecules without the use of metals. Specifically, the use of N- heterocyclic carbenes (NHCs) as organocatalysts is growing due to its biomimetic, nontoxic, and metal-free characteristics. NHC catalysis is a growing field, employing unique lone pair-bearing heterocycles to facilitate a variety of organic transformations, and is used to access useful biologically active molecules, structurally novel compounds, and synthetic building blocks. The origin and inspiration of an NHC as a catalyst is in the human body's biological systems, where Nature uses thiamine, an NHC, to generate acetyl CoA, an important building block for polyketides. The current modes of NHC catalysis are limited to the 1,2-addition onto carbonyl and less common, 1,4-addition onto an 1, 2-unsaturated compound. In order to advance the field of N-heterocyclic carbene catalysis, organocatalysis, and synthetic organic chemistry, there is a need to explore a novel and unusual pathways in chemical reactivity. This new methodology employs a heretofore unexplored avenue of reactions involving the NHC addition to an unconventional electrophile, vinyl sulfone, in creating a reactive partner for chemical reactions. We hypothesize that we can use the novel NHC reactivity to access medicinally, biologically, and synthetically useful molecules in a potentially major advancement in the NHC catalysis field. Specific Aim 1 will focus on the investigation into the mechanism of the NHC-vinyl sulfone, the synthesis of a collection of isoxazolidine compounds, which has exhibited bioactivity as antibacterial agents, and the transformation of these bioactive products into other biologically and/or synthetically valuable molecules. With a better understanding of the NHC-vinyl sulfone reactivity from the mechanistic investigations of Specific Aim 1, Specific Aims 2 and 3 will concentrate on accessing other biologically interesting scaffolds, cyclobutane and more complex cyclic structures, capitalizing on and advancing the synthetic utility of NHCs with an unconventional electrophile.