N-Heterocyclic carbene catalysis: application to the total synthesis of cephalimysin A, and development of multicatalytic cascade reactions
Date
2011
Authors
Lathrop, Stephen Paul, author
Rovis, Tomislav, advisor
Wood, John L., committee member
Crans, Debbie Catharina, committee member
Shores, Matthew P., committee member
Kanatous, Shane B., 1968-, committee member
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Abstract
Application of the N-Heterocyclic carbene catalyzed Stetter reaction to the total synthesis of 9-epi-cephalimysin A has been realized. The approach centers on the use of an asymmetric catalytic Stetter reaction to access the spirocyclic core of cephalimysin A. Specifically it was found that a photoisomerization/Stetter protocol allows rapid access to an intermediate readily amenable for further functionalization. This intermediate was further elaborated to three stereoisomers of the naturally occurring cephalimysin A. During the investigation of cephalimysin A an interesting side product was observed that led to the development of several multicatalytic cascade reactions utilizing N-heterocyclic carbenes. Specifically the pairing of secondary-amine catalysts with N-heterocyclic carbenes allowed for the synthesis of densely functionalized cyclopentanones in a single step. Moreover, a synergistic relationship was observed between the two catalysts. This partnership allowed for the products to be achieved in higher selectivity than would have been possible if conducting the reactions in a stepwise fashion.
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Subject
carbenes
Stetter reaction
cephalimysin A
cascade reactions
benzoin reaction