Chemistry Department Seminar, Richard Mullins, Indiana University, Nov. 7, 1:30 Logan 100
Asymmetric Conjugate Addition Reactions: Application to Natural Product Synthesis
11/07/03The use of the 4-phenyloxazolidinone chiral auxiliary for asymmetric conjugate addition reactions with Yamamoto organocopper reagents has been explored for the preparation of 1,3-syn-dimethyl arrays. As a result of double asymmetric induction, the 1,3-syn-stereoisomers are formed with higher levels of diastereoselectivity relative to their 1,3-anti-counterparts. The application of this methodology for the synthesis of capensifuranone will be discussed.
In the area of asymmetric conjugate addition, relatively little attention has been paid to the Lewis acid promoted conjugate additions of allylstannanes. Using either zirconium(IV) chloride or scandium(III) triflate, the reactions of allyltri-n-butyl stannane with N-enoyl-4-phenyl-oxazolidinones were found to proceed with high diastereoselectivity and in good yield. Surprisingly, the stereochemical outcome of these reactions was opposite to that which was expected based on the widely accepted model for the role played by the chiral auxiliary. The utility of this methodology for the preparation of complex intermediates for natural products total synthesis will be demonstrated.
Richards Mullins received his B.S. degree in Chemistry from Centre College in Danville, Kentucky. He has worked as an NSF-REU Fellow at the University of Michigan and is currently a Ph.D. Candidate at Indiana University. He has taught a number of courses pertaining to organic chemistry and served as a faculty member at Ivy Tech State College. He is a very active member of the American Chemical Society and has served as Chair of the Southern Indiana Section.