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)
Angewandte Chemie