10.1002/anie.201900442
The study presents an enantioselective rhodium-catalyzed allylic alkylation of β,γ-unsaturated α-amino nitriles, offering a novel approach to construct β-stereogenic carbonyl derivatives. This method leverages the catalytic asymmetric alkylation of a homoenolate equivalent, addressing the challenge of manipulating three modes of selectivity: regio- and enantioselectivity, as well as geometrical control. The g-stereogenic cyanoenamine products, resulting from the reaction, can be readily hydrolyzed to yield β-substituted carboxylic acids, providing a convenient pathway to various related carbonyl derivatives. The study underscores the critical role of the E-cyanoenamine products' selective formation, facilitated by the chiral rhodium-allyl intermediate, in achieving high enantiocontrol. The methodology not only provides a practical process but also highlights the utility of molecular dynamics simulation in guiding experimental research for the development of small-molecule inhibitors targeting toxic amyloidogenic protein oligomers.
10.1021/ol901136w
The research explores a method for chain elongation of 1,3-polyols through iterative enantioselective carbonyl allylation under iridium-catalyzed transfer hydrogenation conditions. The purpose is to develop a more efficient and step-economical approach to synthesizing 1,3-polyols by performing carbonyl allylation directly from the alcohol oxidation level, avoiding the use of stoichiometric organometallic reagents and unstable intermediates. Key chemicals used include allyl acetate, various alcohols such as O-benzyl 1,3-propylene glycol and neopentyl glycol, and chiral iridium catalysts modified with ligands like (R)- or (S)-Cl,MeO-BIPHEP. The study concludes that high levels of catalyst-directed enantioselectivity and diastereoselectivity can be achieved, allowing for the iterative synthesis of higher 1,3-polyols with exceptional optical enrichment. This method circumvents the need for multistep preparation of chiral allylmetal reagents and the generation of unstable α-alkoxy aldehydes, demonstrating a concise and efficient route for the synthesis of 1,3-polyols. Future work will focus on developing related C-C bond forming transfer hydrogenations, including imine additions from the amine oxidation level.