Journal of the American Chemical Society, Vol.139, No.50, 18198-18201, 2017
Zn-ProPhenol Catalyzed Enantio- and Diastereoselective Direct Vinylogous Mannich Reactions between alpha,beta- and beta,gamma-Butenolides and Aldimines
We report a Zn-ProPhenol catalyzed reaction between butenolides and imines to obtain tetrasubstituted vinylogous Mannich products in good yield and diastereoselectivity with excellent enantioselectivity (97 to >99.5% ee). Notably, both alpha,beta- and beta,gamma-butenolides can be utilized as nucleophiles in this transformation. The imine partner bears the synthetically versatile N-Cbz group, avoiding the use of the specialized aryl directing groups previously requited in related work. Additionally, the reaction can be performed on gram scale with reduced catalyst loading as low as 2 mol %. The functional group-rich products can be further elaborated using a variety of methods.