Barriers to enantiocontrol in Lewis acid catalyzed hetero-Diels-Alder reactions

ORGN 667

Xiaochen Wang, xiaochen@umd.edu1, Zhuoyan Li1, and Michael P. Doyle, mdoyle3@umd.edu2. (1) Department of Chemistry and Biochemistry, University of Maryland, College Park, College Park, MD 20742, (2) Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742
Increasing the amount of aldehyde in hetero-Diels-Alder reactions with chiral transition metal catalysts leads to a decrease in enantioselectivity. The cause of the decrease is explained by the Lewis acid activity of the coordinated aldehyde. Similar results are obtained when acetonitrile is added to the reaction mixture, but not tetrahydrofuran. Parallel studies were performed with chiral dirhodium carboxamidates, chiral (salen)Cr(III)BF4 and (t-Bu-Box)Cu(II) catalysts.