Enantioselective Rh-Catalyzed Arylation of N-Tosylarylimines with Arylboronic Acids

Chiral diphosphine and monodentate phosphorus ligands on a spiro scaffold for transition-metal-catalyzed asymmetric reactions

The preparation of chiral compounds in enantiomerically pure form is a challenging goal in modern organic synthesis. The use of chiral metal complex catalysis is a powerful, economically feasible tool for the preparation of optically active organic compounds on both laboratory and industrial scales. In particular, the metals coordinated by one or more chiral phosphorus ligands exhibit amazing enantioselectivity and reactivity. Many chiral phosphorus ligands have been synthesized and used in transition-metal-catalyzed asymmetric reactions in past decades. However, a large number of reactions still lack effective chiral ligands, and the enantioselectivities in many reactions are substrate-dependent. The development of effective chiral phosphorus ligands, especially ligands having novel chiral backbones, is still an important task in the area of asymmetric catalysis. Molecules containing a spirocyclic framework are ubiquitous in nature. The synthesis of molecules with this spiro structure can be traced back to 100 years ago. However, the use of this spirocyclic framework to construct chiral phosphorus ligands is a recent event. This Account outlines the design and synthesis of a new family of chiral spiro phosphorus ligands including spiro diphosphines and spiro monodentate phosphorus ligands with 1,1'-spirobiindane and 9,9'-spirobifluorene backbone and their applications in transition-metal-catalyzed asymmetric hydrogenation and carbon-carbon bond formation reactions. The chiral spiro diphosphine lgands SDP with a 1,1'-spirobiindane backbone and SFDP with a 9,9'-spirobifluorene backbone, and the spiro monophosphorus ligands including phosphoramidites, phosphites, phosphonites, and phospholane with a 1,1'-spirobiindane backbone were synthesized in good yields from enantiomerically pure 1,1'-spirobiindane-7,7'-diol and 9,9'-spirobifluoren-1,1'-diol. The ruthenium complexes of chiral spiro diphosphine ligands proved to be very effective catalysts for asymmetric hydrogenations of ketones, alpha-arylaldehydes and alpha,beta-unsaturated acids. The rhodium complexes of chiral spiro monophosphorus ligands are highly enantioselective for the asymmetric hydrogenations of alpha- and beta-dehydroamino acid derivatives, alpha-arylethenyl acetamides and non- N-acyl enamines. The spiro monophosphorus ligands were demonstrated to be highly efficient for the Rh-catalyzed asymmetric addition of arylboronic acids to aldehydes and N-tosylarylimines, Pd-catalyzed asymmetric allylation of aldehydes with allylic alcohols, Cu-catalyzed asymmetric ring opening reactions with Grignard reagents, and Ni-catalyzed asymmetric hydrovinylation of styrene derivatives with ethylene. The chiral spiro phosphorus ligands show high enantioselectivities for a wide range of transition-metal-catalyzed asymmetric reactions. In most of these transformations, the enantioselectivities of spiro phosphorus ligands are superior to those obtained by using the corresponding phosphorus ligands with other backbones. These results arise from the intriguing chiral inducement of spiro structures of the ligands.

Phosphinite- and phosphite-based Type I palladacycles as highly active catalysts for addition reactions of arylboronic acids with aldehydes, α,β-unsaturated ketones, α-ketoesters, and aldimines

Phosphinite- and phosphite-based Type I palladacycle-catalyzed additions of arylboronic acids with aldehydes, α,β-unsaturated ketones, α-ketoesters and aldimines are described. Our study showed that readily available phosphinite- and phosphite-based Type I palladacycles could possess higher catalytic activity than phosphine-based palladacycles and were highly active, practical catalysts. Our study may pave the road for development of optically active phosphinite- and phosphite-based palladacycles for asymmetric catalysis.

Diastereoselective Synthesis of Arylglycine Derivatives by Cationic Palladium(II)-Catalyzed Addition of Arylboronic Acids to N-tert-Butanesulfinyl Imino Esters

A cationic palladium-complex-catalyzed addition of arylboronic acids to N-tert-butanesulfinyl iminoacetates to yield the optically active arylglycine derivatives with moderate to good yield and high diastereoselectivity was developed. This reaction provides a convenient and efficient method for the synthesis of arylglycine derivatives.

Tandem Knoevenagel−Michael Addition of Aryl Sulfonimines with Diethyl Malonate for Synthesis of Arylidene Dimalonates

A highly efficient, one-flask tandem Knoevenagel-Michael addition reaction of sulfonimines with diethyl malonate in the presence of a catalytic amount of base affords the corresponding arylidene dimalonates in good to excellent yields.