Catalytic Access to Succinimide Products Containing Stereogenic Quaternary Carbons

Enantioselective α‐branched aldehyde Michael addition to N‐ phenylmaleimide resulting in non‐stereogenic quaternary carbon containing succinimides is common. Here we emphasize the use of N‐ benzylmaleimide with a focus on stereogenic quaternary carbon formation. In particular, the potassium carboxylate salt of either L‐ iso leucine (L‐ iso Leu) or O− t Bu−L‐threonine (O− t ‐Bu−L‐Thr), 5.0 mol %, proved effective for the formation of α‐quaternary‐β‐tertiary aldehydic succinimide products in high isolated yield (80–97 %) and excellent enantioselectivity (90–99 %). Furthermore, a carbon‐substituted maleimide electrophile has enabled the first example of α‐quaternary carbon formation with β‐ and γ‐stereogenic center formation in 98 % ee , albeit in 40 % yield (product 17 ). From the thirteen formed products, six are reported here for the first time.