Organocatalytic Route to Dihydrocoumarins and Dihydroquinolinones in All Stereochemical Configurations

A straightforward stereodivergent route to dihydrocoumarins and dihydroquinolinones based on cinchona alkaloid catalyzed addition reactions of monothiomalonates (MTMs) to functionalized nitroolefins followed by deprotection and chemoselective cyclization has been developed. The synthesis proceeds under mild conditions and yields heterocycles with adjacent quaternary and tertiary stereogenic centers in very high yields and stereoselectivities. Moreover, full control over the relative and absolute configuration is achieved by the use of (pseudo)enantiomeric catalysts and the difference in reactivity of thioester versus oxoester moieties.