Gold and Palladium Relay Catalytic [4 + 4] Cycloadditions of Enynamides and γ-Methylene-δ-valerolactones: Diastereoselective Construction of Furan-Fused Azacyclooctanes

Visible-Light-Accelerated Decarboxylative N-Allylation of γ-Methylidene-δ-valerolactones via Synergistic Pd(0)/Cu(II)/Riboflavin Catalysis

We report a visible-light-accelerated decarboxylative N-allylation of methylidene-δ-valerolactones via synergistic Pd(0)/Cu(II)/riboflavin catalysis. This method enables efficient coupling of diverse anilines and lactones under mild conditions, achieving an up to 93% yield.

Recent Advances in Sequentially Pd-Catalyzed One-Pot Syntheses of Heterocycles

Sequential Pd-catalyzed one-pot synthetic methodologies have emerged as a powerful and versatile approach in organic synthesis, enabling the construction of complex heterocyclic architectures with high efficiency, selectivity, and atom economy. This review discusses key advancements in multistep, sequentially Pd-catalyzed one-pot processes for accessing heterocyclic derivatives, focusing on classic reactions like Suzuki-Miyaura, Sonogashira, Heck, and hydroamination and extending to specialized techniques such as directed C-H activation. The concatenation of these steps has advanced the scope of one-pot strategies. A section is dedicated to exploring the cooperative use of palladium with other metals, particularly copper, ruthenium, and gold, which has broadened the range of accessible heterocyclic derivatives. Highlighted applications include the synthesis of biologically and pharmaceutically relevant compounds, such as tris(hetero)aryl systems, spiro-oxindoles, and indole derivatives. These one-pot strategies not only streamline synthesis but also align with green chemistry principles by minimizing purification steps and reducing waste and energy consumption. The review also addresses current challenges and limitations in these methodologies, offering insights into ongoing efforts to optimize reaction conditions and expand the applicability of sequential Pd-catalyzed processes.

Synthesis of Heptacyclic Compounds through C-H Bond Activation-Initiated Cascade Reactions

Presented herein is an atom- and step-economical method enabling the precise assembly of a heptacyclic scaffold containing both azocine and indoline units through the cascade reactions of indolin-1-yl(aryl)methanimines with diazo indanediones. The formation of products involves C-H bond activation and double carbene insertion followed by intramolecular condensation, retro-[2 + 2] cycloaddition, and recyclization. This cascade reaction not only provided a concise and straightforward strategy for the synthesis of the otherwise difficult to obtain heptacyclic compounds from readily available substrates but also disclosed an unprecedented reaction mode for indoline derivatives and diazo compounds. In general, this novel synthetic protocol has advantages, such as easily obtainable substrates, structurally sophisticated products, concise synthetic procedure, good compatibility with diverse functional groups, and ready scalability. Moreover, the products thus obtained showed decent antiproliferative activity against three human cancer cell lines.

Recent advances in [4 + 4] annulation of conjugated heterodienes with 1,4-dipolar species for the synthesis of eight-membered heterocycles

Numerous eight-membered heterocycles are of significance in biological chemistry, the pharmaceutical industry, agrochemistry, and materials science. However, the assembly of eight-membered heterocycles is usually challenging due to the unfavorable enthalpic and entropic barriers of the transition states during the ring formation. Tremendous efforts have been devoted to the development of synthetic routes to eight-membered heterocycles. Despite these developments, the exploration of more strategies for the facile and effective assembly of eight-membered heterocyclic molecules in a single vessel under mild conditions is still highly desirable. The conjugated heterodiene-participating [4 + 4] annulation serves as a convenient and robust strategy for the synthesis of eight-membered heterocycles from easily accessible starting materials. In recent years, great progress has been achieved in this attractive field. In this short review, we highlighted the recent advances in the synthesis of eight-membered heterocycles via cascade reactions based on [4 + 4] annulation of conjugated heterodienes with 1,4-dipolar species. The brief backgrounds, the general reactions, the proposed mechanisms and their features are summarized. The prospects and challenges of this field are also outlined at the end of this review. In addition, to highlight the importance and practicality of these reactions, the properties of several series of eight-membered heterocycles have also been introduced briefly.