The copolymerization of carbon dioxide (CO 2 ) and epoxides to produce aliphatic polycarbonates is a burgeoning technology for the large-scale utilization of CO 2 and degradable polymeric materials. Even with the wealth of advancements achieved over the past 50 years on this green technology, many challenges remain, including the use of metal-containing catalysts for polymerization, the removal of the chromatic metal residue after polymerization, and the limited practicable epoxides, especially for those containing electron-withdrawing groups. Herein, we provide kinds of pinwheel-shaped tetranuclear organoboron catalysts for epichlorohydrin/CO 2 copolymerization with >99% polymer selectivity and quantitative CO 2 uptake (>99% carbonate linkages) under mild conditions (25−40 °C, 25 bar of CO 2 ). The produced poly(chloropropylene carbonate) has the highest molecular weight of 36.5 kg/mol and glass transition temperature of 45.4 °C reported to date. The energy difference (ΔE a = 60.7 kJ/mol) between the cyclic carbonate and polycarbonate sheds light on the robust performance of our metal-free catalyst. Control experiments and density functional theory (DFT) calculations revealed a cyclically sequential copolymerization mechanism. The metal-free feature, high catalytic performance under mild conditions, and no trouble with chromaticity for the produced polymers imply that our catalysts are practical candidates to advance the CO 2 -based polycarbonates.

Quaternary ammonium and phosphonium borane bifunctional catalysts have shown high catalytic performance in ring-opening polymerization (ROP) of epoxides to produce polyether. Herein, we systematically investigate a series of well-defined organoboron catalysts by varying the electronic and steric properties of the Lewis acidic boron (B) centers, manipulating the steric hindrance on the ammonium cation (N+), adjusting the distance between B and N+, and regulating the nucleic B number of the catalysts. The investigation on the dinuclear catalysts indicated that the reactivity of a given catalyst could be speculated by its B–N–B angle and the B···B distance. We found that the increase of Lewis acidity and the number of B centers of the organoboron catalysts are useful for a high catalytic activity for ROP of epoxides. The Lewis acidity of the B centers was determined using the acceptor numbers, showing an order of borinane (23.4) > BBN (21.7) > BCy2 (18.8) > Bpin (15.5). Moreover, we demonstrated the production of various telechelic polyols in the presence of different chain transfer agents using the organoboron catalysts. The produced telechelic samples have a well-defined terminal functionality with controllable molecular weight. Lastly, these organoboron catalysts were utilized to produce block copolymers, allyl-terminated macromonomers, and random copolymers.

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The merging of C-H and C-C bond cleavage into one single chemical process remains a daunting challenge, especially in an asymmetric manner. Herein, a Pd(II)-catalyzed enantioselective tandem C-H/C-C activation for the synthesis of axially chiral biaryls is described. Two types of simple cyclopropanes, such as vinylcyclopropanes and cyclopropanols, were used as efficient and readily available coupling partners. This catalytic system features good functional group compatibility, excellent enantiocontrol (up to >99% ee) and the first use of palladium catalyst in this process. The synthetic utility of this protocol was demonstrated by gram-scale synthesis and further synthetic transformations to access various axially chiral biaryls with high enantiopurity. Two distinct but closely related C-C cleavage pathways of cyclopropanes were achieved in the enantioselective C-H/ C-C activation process, which represents a novel platform to further utilize the ring-opening attribute of cyclopropanes in asymmetric catalysis. Preliminary mechanistic studies provide insights into the role of cyclopropanols, which may pave the way for the development of novel catalytic transformations.

We present herein our experimental and DFT computational studies on the directing ability of chalcogenoether motifs in Pd‐catalyzed atroposelective C−H functionalization. The thioether motif was found to be a superior directing group compared to the corresponding ether and selenoether in terms of reactivity and enantiocontrol. Remarkably, DFT calculation provided a predictive model for the optimization of reaction conditions and the interpretation of the origin of enantioselectivity. Both Pd‐catalyzed enantioselective C−H olefination and allylation reactions were successfully developed using chiral phosphoric acids as efficient ligands, providing a broad range of axially chiral biaryls in good yields with excellent enantioselectivities. The highly enantio‐ and diastereoselective construction of polyaryls bearing multiple stereogenic axes, gram‐scale reaction and various chemical transformations make this protocol more attractive and significant.