Highly efficient construction of chiral dispirocyclic oxindole/thiobutyrolactam/chromanone complexes through Michael/cyclization cascade reactions with a rosin-based squaramide catalyst

摘要

An efficient asymmetric Michael/cyclization cascade reaction of 4-chromanones with isothiocyanato oxindoles has been revealed. Under bifunctional organocatalysis by rosin-based squaramide catalyst, a series of spiro[oxindole/thiobutyrolactamichromanone] complexes were conveniently constructed in a highly stereoselective manner (up to 99% yields, 20:1 dr and 99% ee). The reaction leads to the formation of three contiguous stereogenic centers and two Spiro quaternary stereocenters. (C) 2018 Elsevier Ltd. All rights reserved.