Da-Gang Yu

β-Amino acids represent vital structural motifs in bioactive molecules, finding broad utility in organic synthesis, pharmaceuticals, and materials science. Although CO2 has been widely exploited as a C1 carboxyl source for the synthesis of carboxylic acids, the direct aminocarboxylation of unactivated alkenes with CO2 to afford β-amino acids remains largely unexplored and faces formidable challenges. Herein, we report the first photocatalytic aminocarboxylation of unactivated alkenes and heteroarenes using CO2 as the ideal one-carbon feedstock, enabling the efficient synthesis of diverse valuable β-amino acid derivatives. This innovative strategy relies on the sequential installation of a CO2 radical anion and a nitrogen-centered radical (NCR) across alkenes. Specifically, commercially available acyl hydrazides serve as key NCR precursors to form captodative hydrazyl radicals, thereby facilitating selective radical–radical cross-coupling governed by the persistent radical effect (PRE). This methodology readily accommodates simple and abundant chemical feedstocks, ranging from unactivated alkenes (including ethylene) to heteroarenes and activated alkenes. Characterized by low catalyst loading, high selectivity, and good functional-group tolerance, this protocol enables the late-stage derivatization of products into bioactive molecules and various heterocycles.

Carboxylation with CO₂ is one of the most sustainable strategies for synthesizing carboxylic acids. Particularly, the reductive carboxylation of carbonyl derivatives with CO₂ offers a promising route to valuable α-hydroxy acids, α-amino acids and relatives. However, catalytic methods for this transformation remain underexplored and predominantly limited to carboxylation of activated carbonyl derivatives, which rely on the generation of stabilized organometallic intermediates or carbanions to react with CO₂. In this study, we report a reductive carboxylation of unactivated hydrazones with CO₂ via visible-light photocatalysis. Diverse unactivated hydrazones, such as dialkyl substituted ketone hydrazones, cyclic ketone hydrazones and alkyl aldehyde hydrazones, are all suitable for such a carboxylation. The process enables the efficient synthesis of diverse valuable α-hydrazino acids in good yields via selective cleavage of C = N π bond, distinguishing it from prior hydrazone carboxylation methods, which typically involve C = N double bond cleavage. Moreover, this protocol exhibits mild reaction conditions, good functional group tolerance, easy scale up and facile derivatization of products into α-amino acids. Mechanistic investigations and density functional theory (DFT) calculations support the radical addition of CO₂ radical anion to C = N bonds, which represents a unique umpolung strategy for reductive carboxylation with CO₂.

Catalytic carboxylation of ubiquitous C─H bonds with CO ₂ has been demonstrated as a sustainable and streamlined pathway to valuable carboxylic acids. However, the catalytic carboxylation of abundant allylic C(sp ³ )─H bonds with CO ₂ , which presents a unique opportunity to synthesize structurally diverse 3‐butenoic acids, still remains challenging. Herein, we report the first copper metallaphotoredox‐catalyzed formal allylic C(sp ³ )─H carboxylation with CO ₂ , enabling efficient and selective synthesis of 3‐butenoic acids under mild and redox‐neutral conditions. This strategy lies in combining highly reducing photocatalysts to generate alkene radical anion intermediates with copper catalysis to orchestrate regioselective elimination, providing a distinct pathway from traditional allylic C(sp ³ )─H functionalization via forming allyl‐metal intermediates. This method features high atom and step economy, broad substrate scope, good functional group tolerance, facile scalability, and easy access to valuable compounds, including diverse bioactive molecules, natural products, and ¹³ C‐labeled anti‐inflammatory drug sulindac.

Catalytic carboxylation of ubiquitous C─H bonds with CO ₂ has been demonstrated as a sustainable and streamlined pathway to valuable carboxylic acids. However, the catalytic carboxylation of abundant allylic C(sp ³ )─H bonds with CO ₂ , which presents a unique opportunity to synthesize structurally diverse 3‐butenoic acids, still remains challenging. Herein, we report the first copper metallaphotoredox‐catalyzed formal allylic C(sp ³ )─H carboxylation with CO ₂ , enabling efficient and selective synthesis of 3‐butenoic acids under mild and redox‐neutral conditions. This strategy lies in combining highly reducing photocatalysts to generate alkene radical anion intermediates with copper catalysis to orchestrate regioselective elimination, providing a distinct pathway from traditional allylic C(sp ³ )─H functionalization via forming allyl‐metal intermediates. This method features high atom and step economy, broad substrate scope, good functional group tolerance, facile scalability, and easy access to valuable compounds, including diverse bioactive molecules, natural products, and ¹³ C‐labeled anti‐inflammatory drug sulindac.

Aromatic polycarbonates are attractive, high-performance thermoplastic materials. However, it is still a formidable challenge to achieve economical and promising chemical recycling of aromatic polycarbonates. Herein, we prepared two benzo-fused seven-membered cyclic thiocarbonate monomers (M1 and M2) with different sulfur atoms to construct chemically recyclable aromatic poly(thio)carbonates. These monomers underwent efficient DBU-catalyzed polymerization even with a catalyst loading of 0.01 mol %. The resulting aromatic poly(thio)carbonate P(M1) was a semicrystalline material with a T_m of 131 °C, while P(M2) was amorphous with a T_g of 48 °C. In comparison with the commercial aromatic polycarbonates, they showcased enhanced refractive index (n_D = 1.64/1.71), manifesting the benefit of sulfur incorporation into the polymer material. Degradation of the poly(monothio)carbonate led to a mixture of monomer and decarboxylation product. Impressively, P(M2) illustrated efficient SnCl₂-mediated depolymerization via bulk thermal depolymerization, recovering M2 with quantitative yields (>95%).

Poly(α-substituted-β-propiolactone), P(αRPL), is attractive since it is closely related in structure to the biodegradable natural polyhydroxyalkanoates (PHAs). However, the chemical synthesis of isotactic P(αRPL) via ring-opening polymerization has yet to be explored. Herein, we exploited a robust salalen yttrium complex (Y2) as the catalyst to successfully prepare highly isotactic P(αRPL) with P_m > 0.95. These P(αRPL) products exhibited tacticity-dependent thermal and mechanical properties. Remarkably, the highly isotactic P(BPL) containing a benzyl side chain showcased a high melting transition temperature (T_m) of 165 °C. The highly isotactic P(n-BuPL) containing alkyl side chain served as a strong and ductile material comparable to the commercial high-density polyolefins. More importantly, these P(αRPL) products could undergo clean depolymerization to their starting material, α-substituted acrylic acids, offering a closed-loop recycling pathway. This synthetic system allowed access to isotactic P(αRPL), establishing a powerful platform for the discovery of sustainable plastics.

Polymeric properties are intimately entwined with the diversities of structures, making the development of polymerization methods highly valuable to both academic research and industrial applications. Although radical and anionic polymerization techniques have been widely used, both currently have intrinsic limitations. For example, anionic polymerizations heavily rely on highly reactive alkyl metals and alkali metals (e.g., lithium), which involve energy‐intensive synthesis and hazardous handling. Herein, we report a sequential radical‐anionic (co‐)polymerization, where the in situ generation of carbon radicals and carbanions via photoreduction enables augmentation of the monomer repertoire. This approach eliminates lithium dependency and its associated resource, energy, and safety concerns. Mechanistic studies support the sequential radical‐anionic chain‐growing mechanism enabled by photo‐induced consecutive single‐electron transfer reduction. This strategy has the potential to overcome the intrinsic restriction in copolymerizing monomers with electronic property disparities, thereby extending the synthetic utilization of anionic polymerization in polymer science. Furthermore, the process and vulcanization of large‐scale synthesized terminal‐functionalized rubbers further prove the practical applications of this strategy.

Polymeric properties are intimately entwined with the diversities of structures, making the development of polymerization methods highly valuable to both academic research and industrial applications. Although radical and anionic polymerization techniques have been widely used, both currently have intrinsic limitations. For example, anionic polymerizations heavily rely on highly reactive alkyl metals and alkali metals (e.g., lithium), which involve energy‐intensive synthesis and hazardous handling. Herein, we report a sequential radical‐anionic (co‐)polymerization, where the in situ generation of carbon radicals and carbanions via photoreduction enables augmentation of the monomer repertoire. This approach eliminates lithium dependency and its associated resource, energy, and safety concerns. Mechanistic studies support the sequential radical‐anionic chain‐growing mechanism enabled by photo‐induced consecutive single‐electron transfer reduction. This strategy has the potential to overcome the intrinsic restriction in copolymerizing monomers with electronic property disparities, thereby extending the synthetic utilization of anionic polymerization in polymer science. Furthermore, the process and vulcanization of large‐scale synthesized terminal‐functionalized rubbers further prove the practical applications of this strategy.