No abstract

A convergent, catalytic asymmetric formal [4 + 2] annulation for the synthesis of dihydroquinolones has been developed. Carboxylic acids can be employed as precursors to NHC enolates through an in situ activation strategy. Simultaneous generation of a reactive aza-o-quinone methide under the basic conditions employed for NHC generation leads to a dual activation approach.

The first synthesis of heliotropamide is reported. The preparation of this 2-oxopyrrolidine (γ-lactam) natural product relied on a diastereoselective one-pot, four-component reaction (4CR) for the assembly of the core structure. On the basis of chemical shift correlation and NOESY experiments, the previously unknown alkene geometry of heliotropamide is assigned as E.

A reaction between imines and anhydrides has been developed with chiral disubstituted anhydrides and chiral imines. The synthesis of highly substituted γ-lactams with three stereogenic centers, including one quaternary center, proceeds at room temperature in high yield and with high diastereoselectivity in most cases. Enantiomerically pure alkyl-substituted anhydrides proceed with no epimerization, thus providing access to enantiomerically pure penta-substituted lactam products.