Angewandte Chemie - International Edition
Angewandte Chemie - International Edition
4 years ago

Organocatalytic Intramolecular [4+2] Cycloaddition between In Situ Generated Vinylidene ortho-Quinone Methides and Benzofurans

Organocatalytic Intramolecular [4+2] Cycloaddition between In Situ Generated Vinylidene ortho-Quinone Methides and Benzofurans
Hailong Yan, Jun Ao, Jun Deng, Lu Xue, Shiqi Jia, Dongmei Li, Xiaoyan Wu
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. Triple play: The enantioselective construction of oxygen-containing [5-6-5] tricyclic heterocycles by a thiourea-catalyzed asymmetric [4+2] cycloaddition of vinylidene ortho-quinone methides (VQMs) and benzofurans is reported. A series of oxygen-containing [5-6-5] tricyclic heterocycles having various functional groups were synthesized with excellent enantio- and diastereoselectivities.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/anie.201707523

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