This study demonstrates that the annulation of a tetrahydro-1,2-oxazine ring can be realized via bifunctional catalysis, employing nitroolefins and a recently introduced group of aminooxylating reagents as starting materials. The developed cascade reactivity proceeds in a sequence aza-Michael-Michael reaction. The target products, bearing three contiguous stereocenters, have been obtained with high yields (up to 97%) and excellent stereocontrol (>20 : 1 dr, up to 99.5 : 0.5 er).
A novel organocatalytic approach to γ,γ-disubstituted butenolides is described. It is based on a fully site-selective functionalization of 5-alkylidenefuran-2(5H)-ones via trienamine-mediated [4+2]-cycloaddition with α,β,γ,δ-diunsaturated aldehydes. The developed methodology proceeds with excellent stereocontrol and constitutes a unique example of trienamine chemistry with vinylogous dienophiles. Importantly, the reaction has very broad scope and allows for the introduction of substituents also in the α- or the β-position of the butenolide ring. Usefulness of the products obtained has been confirmed in the intramolecular Stetter reaction leading to polycyclic product.
This study demonstrates the design, synthesis, and first application of novel aminooxylating reagents that serve as a useful da synthon equivalents for organic synthesis. It has been demonstrated that their reaction with α,β-unsaturated aldehydes performed under aminocatalytic conditions provides a straightforward access to polysubstituted tetrahydro-1,2-oxazine derivatives, direct precursors of functionalized 1,4-amino alcohols. Target tetrahydro-1,2-oxazine derivatives have been obtained with high yields (up to 89%) and with excellent stereocontrol (up to >20:1 dr, > 99.5:0.5 er). Furthermore, the synthetic usefulness of tetrahydro-1,2-oxazines obtained has been demonstrated in various selective transformations.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.