Symmetry in Cascade Chirality-Transfer Processes: A Catalytic Atroposelective Direct Arylation Approach to BINOL Derivatives

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• 作者：Jin-Zheng Wang ; Jin Zhou ; Chang Xu ; Hongbin Sun ; László Kürti ; Qing-Long Xu
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：April 27, 2016
• 年：2016
• 卷：138
• 期：16
• 页码：5202-5205
• 全文大小：583K
• 年卷期：0
• ISSN：1520-5126

文摘

Herein we disclose a scalable organocatalytic direct arylation approach for the regio- and atroposelective synthesis of non-C₂-symmetric 2,2′-dihydroxy-1,1′-binaphthalenes (BINOLs). In the presence of catalytic amounts of axially chiral phosphoric acids, phenols and naphthols are coupled with iminoquinones via a cascade process that involves sequential aminal formation, sigmatropic rearrangement, and rearomatization to afford enantiomerically enriched BINOL derivatives in good to excellent yields. Our studies suggest that the (local) symmetry of the initially formed aminal intermediate has a dramatic impact on the level of enantioinduction in the final product. Aminals with a plane of symmetry give rise to BINOL derivatives with significantly lower enantiomeric excess than unsymmetrical ones featuring a stereogenic center. Presumably asymmetric induction in the sigmatropic rearrangement step is significantly more challenging than during aminal formation. Sigmatropic rearrangement of the enantiomerically enriched aminal and subsequent rearomatization transfers the central chirality into axial chirality with high fidelity.