Zhang Pengfei, Guo Xing, Liu Chang, Li Wenjun, Li Pengfei
School of Chemistry and Chemical Engineering , Harbin Institute of Technology , Harbin 150080 , P. R. China.
Department of Chemistry and Shenzhen Grubbs Institute , Southern University of Science and Technology , Shenzhen 518055 , P. R. China.
Org Lett. 2019 Jan 4;21(1):152-155. doi: 10.1021/acs.orglett.8b03612. Epub 2018 Dec 21.
The first example of phosphine-catalyzed enantioselective [4 + 1] annulations between 2-enoylpyridine N-oxides and Morita-Baylis-Hillman carbonates is described. When 1,2-bis[(2 R,5 R)-2,5-dimethylphospholano]benzene monoxide is employed as organocatalyst, Morita-Baylis-Hillman carbonates react with 2-enoylpyridine N-oxides smoothly to afford a series of optically active 2,3-dihydrofurans in high yields (up to 96%) with excellent stereoselectivities (96 → 99% ee and >20:1 dr). Importantly, the method offers a facile synthetic approach to enantioenriched pyridine N-oxides featuring 2,3-dihydrofuran motifs.
描述了膦催化2-烯酰基吡啶N-氧化物与森田-贝利斯-希尔曼碳酸酯之间对映选择性[4+1]环化反应的首个实例。当使用1,2-双[(2R,5R)-2,5-二甲基膦杂环戊烷]苯并单氧化物作为有机催化剂时，森田-贝利斯-希尔曼碳酸酯与2-烯酰基吡啶N-氧化物顺利反应，以高收率（高达96%）和优异的立体选择性（96→99%ee和>20:1dr）得到一系列光学活性的2,3-二氢呋喃。重要的是，该方法为具有2,3-二氢呋喃基序的对映体富集吡啶N-氧化物提供了一种简便的合成方法。
