Wang KK, Li YL, Chen R, Wang ZY, Li NB, Zhang LL, Gu S. Substrate-Controlled Regioselectivity Switchable [3 + 2] Annulations To Access Spirooxindole Skeletons.
J Org Chem 2022;
87:8158-8169. [PMID:
35675122 DOI:
10.1021/acs.joc.2c00892]
[Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The additive-free [3 + 2] annulation from isatins, amino acids with 2-styrylbenzoxazoles, was described, providing a series of functional and structurally complex 3,3'-pyrrolidinyl-spirooxindole derivatives containing four contiguous and two quaternary stereogenic centers in high yields (up to 95%) and excellent diastereoselectivities (up to >25:1 dr). Interestingly, the reaction exhibits switchable regioselectivity depending on the substrate of amino acids. With proline or thioproline as the substrate, the reaction afforded α-regioselective spirooxindole skeletons. In contrast, when piperidine acid is the substrate, the reaction provided γ-regioselective spirooxindole skeletons.
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