Asymmetric synthesis of 3,4-dihydrocoumarin motif with an all-carbon quaternary stereocenter via a Michael-acetalization sequence with bifunctional amine-thiourea organocatalysts

Bor-Cherng Hong; Prakash Kotame; Gene-Hsiang Lee

doi:10.1021/ol202331j

Asymmetric synthesis of 3,4-dihydrocoumarin motif with an all-carbon quaternary stereocenter via a Michael-acetalization sequence with bifunctional amine-thiourea organocatalysts

Org Lett. 2011 Nov 4;13(21):5758-61. doi: 10.1021/ol202331j. Epub 2011 Oct 10.

Authors

Bor-Cherng Hong¹, Prakash Kotame, Gene-Hsiang Lee

Affiliation

¹ Department of Chemistry and Biochemistry, National Chung Cheng University, Chia-Yi, 621, Taiwan, ROC. chebch@ccu.edu.tw

PMID: 21985707
DOI: 10.1021/ol202331j

Abstract

Asymmetric domino Michael-acetalization reactions of 2-hydroxynitrostyrene and 2-oxocyclohexanecarbaldehyde with a bifunctional thiourea-tertiary-amine organocatalyst, e.g., the Takemoto catalyst, followed by oxidation providing the 1',3-spiro-2'-oxocyclohexan-3,4-dihydrocoumarin having one all-carbon quaternary stereocenter with excellent diastereo- and enantioselectivities (up to >99% ee), are described. The structures and absolute configurations of the products were confirmed by X-ray analysis.