title: Catalytic Asymmetric [4 + 2] Additions with Aliphatic Nitroalkenes.
abstract: We describe an unprecedented cycloaddition reaction of 2-pyrones with aliphatic nitroalkenes catalyzed by a new bifunctional cinchona alkaloid-derived catalyst bearing a bulky TIPS-ether at the 9-position. The [2.2.2] bicyclic adducts were obtained in good yield with excellent diastereo- and enantioselectivity. Carbon isotope effects were measured by (13)C NMR and are indicative of a stepwise mechanism. Finally, a synthetic application is demonstrated, highlighting the utility of the cycloadducts.
authors.affiliation: Department of Chemistry, Brandeis University, Waltham, MA, 02454-9110, USA.
authors.forename: Keith J
authors.initials: KJ
authors.lastname: Bartelson
authors.forename: Ravi P
authors.initials: RP
authors.lastname: Singh
authors.forename: Bruce M
authors.initials: BM
authors.lastname: Foxman
authors.forename: Li
authors.initials: L
authors.lastname: Deng