Efficient asymmetric syntheses of α-quaternary lactones and esters through chiral bifunctional sulfide-catalyzed desymmetrizing bromolactonization of α,α-diallyl carboxylic acids

Fabrication strategies for chiral self-assembly surface

Chiral self-assembly is the spontaneous organization of individual building blocks from chiral (bio)molecules to macroscopic objects into ordered superstructures. Chiral self-assembly is ubiquitous in nature, such as DNA and proteins, which formed the foundation of biological structures. In addition to chiral (bio) molecules, chiral ordered superstructures constructed by self-assembly have also attracted much attention. Chiral self-assembly usually refers to the process of forming chiral aggregates in an ordered arrangement under various non-covalent bonding such as H-bond, π-π interactions, van der Waals forces (dipole-dipole, electrostatic effects, etc.), and hydrophobic interactions. Chiral assembly involves the spontaneous process, which followed the minimum energy rule. It is essentially an intermolecular interaction force. Self-assembled chiral materials based on chiral recognition in electrochemistry, chiral catalysis, optical sensing, chiral separation, etc. have a broad application potential with the research development of chiral materials in recent years.

trans-Cyclooctenes as Scavengers of Bromine Involved in Catalytic Bromination

Scavengers that capture reactive chemical substances are used to prevent the decomposition of materials. However, in the field of catalysis, the development of scavengers that inhibit background pathways has attracted little attention, although the concept will open up an otherwise inaccessible reaction space. In catalytic bromination, fast non-catalyzed background reactions disturb the catalytic control of the selectivity, even when using N-bromoamide reagents, which have a milder reactivity than bromine (Br2 ). Here, we developed a trans-cyclooctene (TCO) bearing a 2-pyridylethyl group to efficiently retard background reactions by capturing Br2 in bromocyclization using N-bromosuccinimide. The use of less than a stoichiometric amount of the TCO was sufficient to inhibit non-catalyzed reactions, and mechanistic studies using the TCO revealed that in situ-generated Br2 provides non-catalyzed reaction pathways based on a chain mechanism. The TCO is useful as an additive for improving enantioselectivity and regioselectivity in catalytic reactions. Cooperative systems using the TCO with selective catalysts offer an alternative strategy for optimizing catalyst-controlled selectivity during bromination. Moreover, it also served as an indicator of Br2 involved in catalytic reaction pathways; thus, the TCO was useful as a probe for mechanistic investigations into the involvement of Br2 in bromination reactions of interest.

Catalytic asymmetric CO2 utilization reaction for the enantioselective synthesis of chiral 2-oxazolidinones

Catalytic asymmetric bromocyclizations of in situ generated carbamic acids from CO₂ and allylamines were achieved via the use of a BINOL-derived chiral bifunctional selenide catalyst bearing a hydroxy group. Chiral 2-oxazolidinone products as important pharmaceutical building blocks were obtained with good enantioselectivities by the present catalytic asymmetric CO₂ utilization reactions.

Asymmetric Synthesis of α-Spiro-γ-lactones and α-Substituted γ-Lactones via Chiral Bifunctional Sulfide-Catalyzed Bromolactonizations

An efficient enantioselective synthesis of γ-chiral α-spiro-γ-lactones, which are important building blocks for pharmaceuticals, was achieved via BINOL-derived chiral bifunctional sulfide-catalyzed bromolactonizations of α-allyl carboxylic acids containing either hetero- or carbocyclic structures. Transformations of the resultant α-spiro-type bromolactonization product were examined to obtain optically active γ-functionalized α-spiro-γ-lactones. The utility of this catalytic system was also demonstrated in the asymmetric synthesis of α,α-diaryl- and dialkyl-substituted γ-lactones.