DFT-Based Stereochemical Rationales for the Bifunctional Brønsted Acid/Base-Catalyzed Diastereodivergent and Enantioselective aza-Henry Reactions of α-Nitro Esters.

A pair of chiral bis(amidine) [BAM] proton complexes provide reagent (catalyst)-controlled, highly diastereo- and enantioselective direct aza-Henry reactions leading to α-alkyl-substituted α,β-diamino esters. A -symmetric ligand provides high -selectivity, while a nonsymmetric congener exhibits -selectivity in this example of diastereodivergent, enantioselective catalysis. A detailed computational analysis is reported for the first time, one that supports distinct models for selectivity resulting from the more hindered binding cavity of the -symmetric ligand.

Diversity-oriented synthesis of glycomimetics.

Glycomimetics are structural mimics of naturally occurring carbohydrates and represent important therapeutic leads in several disease treatments. However, the structural and stereochemical complexity inherent to glycomimetics often challenges medicinal chemistry efforts and is incompatible with diversity-oriented synthesis approaches. Here, we describe a one-pot proline-catalyzed aldehyde α-functionalization/aldol reaction that produces an array of stereochemically well-defined glycomimetic building blocks containing fluoro, chloro, bromo, trifluoromethylthio and azodicarboxylate functional groups.

Oxidative Rearrangement of MIDA (-Methyliminodiacetic Acid) Boronates: Mechanistic Insights and Synthetic Applications.

Herein we report that coordinative hemilability allows the MIDA (-methyliminodiacetic acid) nitrogen to behave as a nucleophile and intramolecularly intercept palladium π-allyl intermediates. A mechanistic investigation indicates that this rearrangement proceeds through an S2-like displacement at tetrasubstituted boron to furnish novel DABN boronates. Oxidative addition into the N-C bond of the DABN scaffold furnishes borylated π-allyl intermediates that can then be trapped with a variety of nucleophiles, including in a three-component coupling.

Discovery and Mechanistic Study of a Totally Organic C-COxygen Insertion Reaction.

We report an unprecedented photochemical oxygen insertion reaction into an aromatic quinone methide. Insertion happens specifically within a C-C bond, whereas the quinone methide moiety remains intact itself. Detailed mechanistic studies, supported by DFT calculations, support a pathway in which the -QM plays a pivotal activating role.

Ligand Effect in Alkali-Metal-Catalyzed Transfer Hydrogenation of Ketones.

This work unveils the reactivity patterns, as well as ligand and additive effect on alkali-metal-base-catalyzed transfer hydrogenation of ketones. Crucially to this reactivity is the presence of a Lewis acid (alkali cation), as opposed to a simple base effect. With aryl ketones, the observed reactivity order is Na >Li >K , whereas for aliphatic substrates it follows the expected Lewis acidity, Li >Na >K .