Enantioselective Synthesis of Spiro Heterocyclic Compounds Using a Combination of Organocatalysis and Transition-Metal Catalysis

Asymmetric three-component Tsuji-Trost allylation reaction enabled by chiral aldehyde/palladium combined catalysis

Despite the long-standing exploration of the catalytic asymmetric Tsuji-Trost allylation reaction since the mid-20th century, most reported instances have adhered to a two-component approach. Here, we present a remarkably efficient three-component asymmetric allylation reaction enabled by the collaborative action of chiral aldehyde and palladium. A diverse array of NH2-unprotected amino acid esters, aryl or alkenyl iodides, and allyl alcohol esters exhibit robust participation in this reaction, resulting in the synthesis of structurally diverse non-proteinogenic α-amino acid esters with favorable experimental outcomes. Mechanistic investigations reveal the dominance of the allylation/Heck coupling cascade in reactions involving electron-rich aryl iodides, while the Heck coupling/allylation cascade emerges as the dominant pathway in reactions involving electron-deficient aryl iodides. This chiral aldehyde/palladium combining catalytic system precisely governs the chemoselectivity of C-allylation and N-allylation, the regioselectivity of linear and branched allylation, and the enantioselectivity of C-allylation products.

Copper-catalyzed asymmetric allylic substitution of racemic/meso substrates

The synthesis of enantiomerically pure compounds is a pivotal subject in the field of chemistry, with enantioselective catalysis currently standing as the primary approach for delivering specific enantiomers. Among these strategies, Cu-catalyzed asymmetric allylic substitution (AAS) is significant and irreplaceable, especially when it comes to the use of non-stabilized nucleophiles (pK a > 25). Although Cu-catalyzed AAS of prochiral substrates has also been widely developed, methodologies involving racemic/meso substrates are highly desirable, as the substrates undergo dynamic processes to give single enantiomer products. Inspired by the pioneering work of the Alexakis, Feringa and Gennari groups, Cu-catalyzed AAS has been continuously employed in deracemization and desymmetrization processes for the synthesis of enantiomerically enriched products. In this review, we mainly focus on the developments of Cu-catalyzed AAS with racemic/meso substrates over the past two decades, providing an explicit outline of the ligands employed, the scope of nucleophiles, the underlying dynamic processes and their practical applications.

Advances in heterocycle synthesis through photochemical carbene transfer reactions

Heterocyclic skeletons are commonly found in various bioactive molecules and pharmaceutical compounds, making them crucial in areas such as medicinal chemistry, materials science, and the realm of natural product synthesis. In recent years, the rapid advancements of visible light methodologies in organic synthesis have shown promising potential for the development of light-induced carbene transfer reactions. This is particularly significant as most organic molecules do not absorb visible light. Free carbene, known for its high activity, is frequently utilized for insertion reactions or cyclopropanation reactions. This review focuses on the photochemical strategy for the construction of heterocyclic skeletons, specifically highlighting the methods that employ visible light-promoted carbene transfer reactions.

Core Structure-Oriented Asymmetric α-Allenylic Alkylation of Amino Acid Esters Enabled by Chiral Aldehyde/Palladium Catalysis

Aiming at the reported chiral synthons leading to manzacidins A and D, here we report a highly efficient catalytic asymmetric α-allenylic alkylation reaction of NH2-unprotected amino acid esters that is promoted by combined chiral aldehyde/palladium catalysis. Fifty examples of unnatural α,α-disubstituted amino acid esters are reported with good-to-excellent yields and stereoselectivities. Based on this methodology, a key intermediate leading to manzacidin C and its other three stereoisomers is prepared accordingly.

Recent Progress in the Synthesis of Silaspiranes

Silaspiranes bearing a spiro-silicon center are promising ring frameworks for the synthesis of novel spirocyclic molecules possessing unique properties. Development of efficient methods towards these ring structures has therefore attracted considerable attentions of synthetic chemists. This minireview highlights the representative advances in the field, and is categorized into four parts according to the ring formation strategies: cyclization, annulation, ring expansion and cycloaddition.

Asymmetric α-Allylation of N-Unprotected Amino Acid Esters with 1,3-Disubstituted Allyl Acetates Enabled by Chiral-Aldehyde/Palladium Catalysis

A chiral aldehyde/palladium catalysis-enabled asymmetric α-allylation of NH2-unprotected amino acid esters with 1,3-disubstituted allyl acetates is described in this work. With the utilization of different chiral phosphine ligands, both the anti- and syn-selective allylation reactions are achieved enantioselectively. A series of α,α-disubstituted amino acid esters bearing two adjacent chiral centers are produced in moderate-to-excellent yields, diastereoselectivities, and enantioselectivities.

Chiral Aldehyde-Palladium Catalysis Enables Asymmetric Synthesis of α-Alkyl Tryptophans via Cascade Heck-Alkylation Reaction

The first catalytic asymmetric cascade Heck-alkylation reaction of NH₂-unprotected amino acid esters with N-(2-iodophenyl)allenamides is reported in this work. Under the promotion of a combining catalytic system comprising a chiral aldehyde, a chiral palladium complex, and the Lewis acid ZnCl₂, the title reaction takes place smoothly, giving optically active α-alkyl tryptophan derivatives in moderate to good yields and excellent enantioselectivities. The target products can be converted into other structurally complex chiral indoles without the loss of enantioselectivities.