Enantioselective Syntheses of C2-Symmetric Pyrazolones and Diones via One-Pot Organo-/Iodine Sequential Catalysis.

The catalytic diastereo- and enantioselective syntheses of C2-symmetric axially chiral 1,4-dicarbonyl derivatives with 2,3-quaternary stereocenters were achieved by utilizing an organo-/iodine binary catalytic strategy. The reactions proceeded well under mild conditions without metals or strong bases.

Merging catalyst-free synthesis and iodine catalysis: one-pot synthesis of dihydrofuropyrimidines and spirodihydrofuropyrimidine pyrazolones.

A new and efficient one-pot strategy combining catalyst-free synthesis and iodine catalysis has been developed for the synthesis of dihydrofuropyrimidines and spirodihydrofuropyrimidine pyrazolones. This approach affords products in moderate to high yields (up to 96%) with excellent diastereoselectivities (up to >25 : 1 dr). The reaction is simple to carry out and is metal-free.

Combining Organocatalysis and Iodine Catalysis: One-Pot Sequential Catalytic Synthesis of Chiral Spirodihydrobenzofuran Pyrazolones and Spirodihydrobenzofuran Oxindoles.

A new and efficient catalytic strategy that combines asymmetric organocatalysis and iodine catalysis was first developed for the one-pot Michael/iodization/SN2 nucleophilic substitution sequential catalytic synthesis of spirodihydrobenzofuran pyrazolones and spirodihydrobenzofuran oxindoles. The approach results in products with moderate to high yields (up to 93%), high to excellent enantioselectivities (up to 99% ee), and excellent diastereoselectivities (up to >99:1 dr). The reaction features simple operation and is metal-free and base-free.

Asymmetric synthesis of polysubstituted chiral chromans via an organocatalytic oxa-Michael-nitro-Michael domino reaction.

A catalytic asymmetric method for the synthesis of polysubstituted chromans via an oxa-Michael-nitro-Michael reaction has been developed. The squaramide-catalyzed domino reaction of 2-hydroxynitrostyrenes with trans-ß-nitroolefins produced chiral chromans with excellent enantioselectivities (up to 99% ee), diastereoselectivities (up to >20 : 1 dr), and moderate to good yields (up to 82%).

One-pot asymmetric synthesis of a spiro[dihydrofurocoumarin/pyrazolone] scaffold by a Michael addition/I2-mediated cyclization sequence.

An asymmetric formal one-pot reaction of 4-hydroxycoumarins with unsaturated pyrazolones has been developed by merging a chiral bifunctional organocatalyst with molecular iodine, which furnished a series of optically active spiro[dihydrofurocoumarin/pyrazolone] heterocycles with spiro quaternary stereogenic centers in moderate to excellent yields (up to 99%) with excellent diastereoselectivities (up to >99 : 1 dr) and good to excellent enantioselectivities (up to 99% ee). The application in the gram-scale synthesis of chiral spiro[dihydrofurocoumarin/pyrazolone] compounds was also successfully realized.