Palladium-Catalyzed Ligand-Controlled Switchable Hetero-(5 + 3)/Enantioselective [2σ+2σ] Cycloadditions of Bicyclobutanes with Vinyl Oxiranes

• Published in: Journal of the American Chemical Society Vol. 146; no. 29; pp. 19621 - 19628
• Main Authors: Zhou, Jin-Lan, Xiao, Yuanjiu, He, Linke, Gao, Xin-Yu, Yang, Xue-Chun, Wu, Wen-Biao, Wang, Guoqiang, Zhang, Junliang, Feng, Jian-Jun
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 24.07.2024
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.4c01851

For nearly 60 years, significant research efforts have been focused on developing strategies for the cycloaddition of bicyclobutanes (BCBs). However, higher-order cycloaddition and catalytic asymmetric cycloaddition of BCBs have been long-standing formidable challenges. Here, we report Pd-catalyzed ligand-controlled, tunable cycloadditions for the divergent synthesis of bridged bicyclic frameworks. The dppb ligand facilitates the formal (5+3) cycloaddition of BCBs and vinyl oxiranes, yielding valuable eight-membered ethers with bridged bicyclic scaffolds in 100% regioselectivity. The Cy-DPEphos ligand promotes selective hetero-[2σ+2σ] cycloadditions to access pharmacologically important 2-oxabicyclo[3.1.1]­heptane (O-BCHeps). Furthermore, the corresponding catalytic asymmetric synthesis of O-BCHeps with 94–99% ee has been achieved using chiral (S)-DTBM-Segphos, representing the first catalytic asymmetric cross-dimerization of two strained rings. The obtained O-BCHeps are promising bioisosteres for ortho-substituted benzenes.