Proximal Ester Assistance vs. Stereoelectronic Prohibition in Catalytic N-Acyliminium Ion Reactions: Stereoselective Formation of Aza-Heterocycles with Two Contiguous Quaternary-Tertiary Stereocenters
Formal [3+2]-Cycloaddition-Based Approach Using Ethoxymethylene Malonate Derivatives: Novel and Expedient Access to Functionalized N-Acyliminium Precursors