Organocatalytic Intramolecular [4+2] Cycloaddition between In Situ Generated Vinylidene ortho‐Quinone Methides and Benzofurans. (27th September 2017)

• Record Type: Journal Article
• Authors: Wu, Xiaoyan; Xue, Lu; Li, Dongmei; Jia, Shiqi; Ao, Jun; Deng, Jun; Yan, Hailong
• Is Part Of: Angewandte Chemie. Volume 129:Number 44(2017)
• Page Start: 13910
• Page End: 13914
• Publication Date: 2017-09-27
• Subjects: Cycloadditionen -- Heterocyclen -- Organokatalyse -- Polycyclen -- Umlagerungen; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.201707523
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: Described herein is the enantioselective construction of oxygen‐containing [5‐6‐5] tricyclic heterocycles by an organocatalyzed asymmetric [4+2] cycloaddition of vinylidene ortho ‐quinone methides and benzofurans. According to this methodology, a series of oxygen‐containing [5‐6‐5] tricyclic heterocycles with various functional groups were synthesized in excellent enantio‐ and diastereoselectivities (>99 % ee, >20:1 d.r.). Furthermore, the deuterium‐labeling experiments and high‐resolution mass spectroscopy demonstrated that a vinylidene ortho ‐quinone methide intermediate was involved and possibly resulted from a prototropic rearrangement of 2‐ethynylphenol. Remarkably, a catalyst loading as low as 0.1 mol %, and a gram‐scale synthesis were achieved for this transformation.