Dang Hang T, Nguyen Viet D, Haug Graham C, Vuong Ngan T H, Arman Hadi D, Larionov Oleg V
Department of Chemistry, The University of Texas at San Antonio, San Antonio, Texas 78249, United States.
ACS Catal. 2021 Feb 5;11(3):1042-1052. doi: 10.1021/acscatal.0c05574. Epub 2021 Jan 7.
Development of stereoselective and efficient reactions for construction of conjugated dienes and polyenes has remained at the forefront of organic chemistry, due to their key roles in medicinal chemistry, organic synthesis, and materials science. The synthesis of conjugated dienes and polyenes is typically accomplished in a multistep manner by sequential installation of individual C=C bonds because it allows for control of stereoselectivity and efficiency of formation of each double bond. A conceptually distinct dienylation approach entails a stereoselective appendage of a four-carbon unit, shortcutting diene synthesis. Dienylation with sulfolene provided a direct route to -dienes, but the synthesis of substantially more challenging -dienes remained elusive. Here, we report that a highly Z-selective dienylation can be now achieved by a simple adjustment of a ligand, enabling stereodivergent synthesis of - and -dienes from one reagent and in one step. A detailed mechanistic investigation of the - and -selective dienylation provided insight into the divergent behavior of the two catalytic systems and revealed that differences in relative stabilities of catalytically active palladium phosphine complexes have a major impact on the stereochemical outcomes of the dienylation.
由于共轭二烯和多烯在药物化学、有机合成及材料科学中发挥着关键作用，因此开发用于构建共轭二烯和多烯的立体选择性高效反应一直处于有机化学的前沿。共轭二烯和多烯的合成通常通过依次安装单个碳 - 碳双键以多步方式完成，因为这样可以控制每个双键形成的立体选择性和效率。一种概念上不同的双烯化方法是通过立体选择性地连接一个四碳单元来简化二烯合成。用环丁烯砜进行双烯化提供了一条合成γ-二烯的直接途径，但合成更具挑战性的δ-二烯仍然难以实现。在此，我们报道通过简单调整配体现在可以实现高度Z选择性双烯化，能够从一种试剂一步实现γ-和δ-二烯的立体发散合成。对γ-和δ-选择性双烯化进行的详细机理研究深入了解了两种催化体系的不同行为，并揭示了催化活性钯膦配合物相对稳定性的差异对双烯化的立体化学结果有重大影响。
