南京大学史壮志/郑文华Sci. Bull.:平面手性[2.2]对环蕃联芳基膦(PCP-BPhos)的合理设计、催化合成和应用
图1. TOC (图片来源于Sci. Bull.)The advent of privileged chiral ligands has marked a transformative milestone in the realm of asymmetric catalysis, underscoring the imperative for developing efficient synthetic methodologies to access these compounds. Such advancements are crucial for the rapid generation of diverse chemical libraries endowed with varied steric and electronic properties. In this study, we unveil a highly efficient and streamlined approach for the construction of a broad spectrum of planar chiral [2.2]paracyclophane biarylphosphine (PCP-BPhos) ligands. Our innovative strategy leverages P(III)-directed C–H activation, which entails the direct arylation of triarylphosphines with enantiomerically enriched PCP bromides. A cornerstone of this methodology is the intrinsic phosphine moiety within the substrates, which serves as a directing group, thereby facilitating the formation of a benzo-fused four-membered metallacycle during the catalytic cycle. These in situ modified chiral ligands have exhibited exceptional efficacy in Pd-catalyzed asymmetric allylic alkylation and Suzuki-Miyaura coupling, underscoring their potential for widespread applications in asymmetric catalysis. Our comprehensive experimental and computational studies provide detailed mechanistic insights into these transformations, further elucidating the underlying principles of these catalytic processes.图2. 研究背景及本策略 (图片来源于Sci. Bull.)图3. 条件优化 (图片来源于Sci. Bull.)图4. 合成PCP-BPhos配体库 (图片来源于Sci. Bull.)图5. PCP-BPhos配体在不对称催化中的应用 (图片来源于Sci. Bull.)图6. 机理研究 (图片来源于Sci. Bull.)图7. DFT计算可能的催化循环 (图片来源于Sci. Bull.)We have devised a novel approach to synthesize a family of PCP-BPhos through rhodium-catalyzed direct arylation. Throughout this endeavor, the intrinsic phosphine moiety within the substrates acts as the directing group, facilitating the formation of the benzo-fused four-membered metallacycle during the catalytic cycle. This developed methodology marks a significant advancement in C–H activation, particularly in its application to chiral ligand synthesis, ensuring exceptional atom economy, operational simplicity, and redox efficiency. We envisage that this work will not only inspire the design of novel phosphine ligands but also address the persistent challenges in the realm of C–H activation, thereby paving the way for extensive applications and innovations in asymmetric catalysis.
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