Organocatalytic Domino Oxa‐Michael/1,6‐Addition Reactions: Asymmetric Synthesis of Chromans Bearing Oxindole Scaffolds

• DOI: 10.1002/ange.201606947
• Publication Date: 2016-09-07T11:05:38Z
• Authors: Kun Zhao; Ying Zhi; Tao Shu; Arto Valkonen; Kari Rissanen; Dieter Enders
• Keywords: Domino; Stereocenter; Oxindole; Isatin; Cascade reaction; Michael reaction

Abstract An asymmetric organocatalytic domino oxa‐Michael/1,6‐addition reaction of ortho ‐hydroxyphenyl‐substituted para ‐quinone methides and isatin‐derived enoates has been developed. In the presence 5 mol % a bifunctional thiourea organocatalyst, this scalable affords 4‐phenyl‐substituted chromans bearing spiro‐connected oxindole scaffolds three adjacent stereogenic centers in good to excellent yields (up 98 %) with very high stereoselectivities >20:1 d.r., >99 ee ).