Asymmetric Formal Carbonyl-Ene Reactions of Formaldehyde <i>tert</i>-Butyl Hydrazone with α‑Keto Esters: Dual Activation by Bis-urea Catalysts

The dual activation of α-keto esters and formaldehyde tert-butyl hydrazone by BINAM-derived bis-ureas is the key to achieve high reactivity and excellent enantioselectivities in nucleophilic addition (formal carbonyl-ene reaction) to functionalized tertiary carbinols. Ensuing high-yielding diazene-to-aldehyde tranformations and subsequent derivatizations provides a direct entry to a variety of densely functionalized products.