Lithium Binaphtholate-Catalyzed Asymmetric Addition of Lithium Acetylides to Carbonyl Compounds

Chiral Macrocyclic Catalysts for the Enantioselective Addition of Lithium Acetylides to Ketones

Alkynyl addition to carbonyl compounds is a valuable synthetic method for the preparation of versatile chiral alcohols that are widely found in pharmaceuticals and natural products. Although a variety of enantioselective variations have been reported, alkynyl addition to simple ketones remains an unmet challenge due to their low reactivity and difficult enantiofacial discrimination. Here, we report a method for the catalytic enantioselective addition of lithium acetylide to a variety of ketones using macrocyclic lithium binaphtholates as catalysts. These reactions generally suffer from facile aggregation of lithium species, which leads to less active and selective catalysts. The macrocyclic structure designed in this study prevents such aggregation, affording a monomeric and highly active catalyst that can furnish enantioenriched tertiary alcohols from a variety of ketones within 5-30 min. Moreover, the confined cavity and lipophilicity of the macrocycle confer substrate specificity on the system, demonstrating a multiselectivity similar to that of enzymatic reactions. Thus, these findings offer new insights into the rational design of small-molecule artificial enzymes that exhibit high levels of reactivity and multiselectivity.

Kinetic Resolution of Azaarylethynyl Tertiary Alcohols by Chiral Brønsted Acid Catalysed Phosphine-Mediated Deoxygenation

A chiral Brønsted acid catalysed phosphine-mediated deoxygenation protocol is reported. This metal-free method provides a precise kinetic resolution platform for azaarylethynyl tertiary alcohols, which are a broad category of biologically and synthetically important azaarene derivatives. In addition to providing an efficient method for the first asymmetric preparation of these tertiary alcohols, the strategy facilitates the construction of azaaryl-functionalized allenes with good to excellent enantioselectivities. The high selectivity factors (s up to 235), broad substrate scope, and ability to convert azaaryl compounds into both chiral tertiary alcohols and allenes robustly underscore the efficiency and promising utility of this method. The practicability is further validated by the successful synthesis of deuterated allenes with high ee values and substantial incorporation of deuterium using inexpensive D₂ O as the deuterium source.

Chiral tertiary propargylic alcohols via Pd-catalyzed carboxylative kinetic resolution

A highly efficient Pd/H⁺-cocatalyzed kinetic resolution reaction of tertiary propargylic alcohols has been reported.

Merging Asymmetric [1,2]-Additions of Lithium Acetylides to Carbonyls with Type II Anion Relay Chemistry

An enantioselective three-component coupling reaction has been developed, enabling the union of a variety of lithium acetylides and electrophiles exploiting an achiral linchpin via an anionic reaction cascade. This Type II Anion Relay Chemistry tactic is initiated via an enantioselective [1,2]-carbonyl addition exploiting BINOL catalysis to access an enantioenriched alkoxide intermediate. Migration of charge across the linchpin via a [1,4]-Brook rearrangement with electrophile capture affords a three-component propargyl ether adduct. Herein, we report the development, scope, and limitations of this reaction sequence.

Lithium Binaphtholate-Catalyzed Michael Reaction of Malonates with Maleates and Its Application to the Enantioselective Synthesis of Tricarboxylic Acid Derivatives

The Michael reaction of malonates with maleates afforded the corresponding adducts in high yields with high enantioselectivities (up to 98% enantiomeric excess (ee)) by using dilithium 3,3'-dichlorobinaphtholate as a catalyst. The obtained Michael adducts could be converted to optically active tricarboxylic acid (TCA) derivatives via the Krapcho reaction.

Copper-catalyzed oxidative coupling of quinoxalin-2(1H)-ones with alcohols: access to hydroxyalkylation of quinoxalin-2(1H)-ones

An efficient protocol for the synthesis of hydroxyl-containing quinoxalin-2(1H)-ones has been developed via the copper-catalyzed cross-coupling reaction of quinoxalin-2(1H)-ones with alcohols with moderate to good yields.

Palladium/H+-cocatalyzed kinetic resolution of tertiary propargylic alcohols

A new concept for the synthesis of optically active tertiary propargylic alcohols with 90–99% ee through palladium/H⁺-cocatalyzed kinetic resolution was developed.

Base-promoted direct and highly selective alkynylation of electron-deficient octafluorotoluene

Experimental and theoretical studies are reported on the base-promoted direct alkynylation of octafluorotoluene via highly selective C–F bond cleavage.