Organocatalytic Domino Oxa-Michael/1,6-Addition Reactions: Asymmetric Synthesis of Chromans Bearing Oxindole Scaffolds.
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 of 5 mol % of a bifunctional thiourea organocatalyst, this scalable domino reaction affords 4-phenyl-substituted chromans bearing spiro-connected oxindole scaffolds and three adjacent stereogenic centers in good to excellent yields (up to 98 %) and with very high stereoselectivities (up to >20:1 d.r., >99 % ee).
Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany.
Kun
K
Zhao
Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany.
Ying
Y
Zhi
Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany.
Tao
T
Shu
Department of Chemistry, Nanoscience Center, University of Jyvaskyla, 40014, JYU, Finland.
Arto
A
Valkonen
Department of Chemistry, Nanoscience Center, University of Jyvaskyla, 40014, JYU, Finland.
Kari
K
Rissanen
Institute of Organic Chemistry, RWTH Aachen University, Landoltweg 1, 52074, Aachen, Germany. enders@rwth-aachen.de.
Dieter
D
Enders
chromans; domino reactions; organocatalysis; oxa-Michael addition; para-quinone methides