Catalytic Asymmetric Formal [3+3] Cycloaddition of an Azomethine Ylide with 3‐Indolylmethanol: Enantioselective Construction of a Six‐Membered Piperidine Framework |
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| Authors: | Prof?Dr Feng Shi Ren‐Yi Zhu Wei Dai Cong‐Shuai Wang Prof Shu‐Jiang Tu |
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| Affiliation: | School of Chemistry and Chemical Engineering, Jiangsu Normal University, Xuzhou, 221116 (China), Fax: (+86)?516‐83500065 |
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| Abstract: | A catalytic asymmetric formal 3+3] cycloaddition of 3‐indolylmethanol and an in situ‐generated azomethine ylide has been established to construct a chiral six‐membered piperidine framework with two stereogenic centers. This approach not only represents the first enantioselective cycloaddition of isatin‐derived 3‐indolylmethanol, but also has realized an unusual enantioselective formal 3+3] cycloaddition of azomethine ylide rather than its common 3+2] cycloadditions. Besides, this protocol combines the merits of a multicomponent reaction and organocatalysis, which efficiently assembles a variety of isatin‐derived 3‐indolylmethanols, aldehydes, and amino esters into structurally diverse spiroindoline‐3,4′‐pyridoindoles] with one all‐carbon quaternary stereogenic center in high yields and excellent enantioselectivities (up to 93 % yield, >99 % enantiomeric excess (ee)). Although the diastereoselectivity of the reaction is generally moderate, most of the diastereomers can be separated by using column chromatography followed by preparative TLC. |
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| Keywords: | asymmetric synthesis cycloaddition enantioselectivity multicomponent reactions organocatalysis ylides |
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