The copper complexes of chiral spiro phosphoramidite and phosphite ligands were found to be effective catalysts in the asymmetric allylic alkylations of cinnamyl halides with dialkylzincs. The allylic alkylation products were obtained in high regioselectivities (SN2/SN2 up to 98:2) and enantiomeric excesses of up to 74% for SN2 products.

Optically active a-arylalkylamines are an important class of compounds that are widely used in organic and pharmaceutical synthesis, and much effort has been made to develop efficient asymmetric synthetic methods for them. [1] Asymmetric catalytic hydrogenation of enamides, initiated by Kagan et al., [2] provides a direct and convenient route to chiral amine derivatives. However, many well-known chiral diphosphane ligands, such as DIOP, BINAP, and CHIRAPHOS, which are extremely successful in the asymmetric hydrogenation of dehydroamino acid derivatives, do not give high enantioselectivity in the hydrogenation of enamides.[3, 4] A breakthrough was achieved by Burk et al. [4a] with the introduction of BPE and DuPHOS ligands, which gave excellent enantioselectivity in the Rh-catalyzed asymmetric hydrogenation of enamides. Lately, some other P ligands were also reported to be efficient in the hydrogenation of enamides. [4b, 5] However, all ligands that gave a high degree of enantiocontrol are bidentate. To our knowledge, no efficient chiral monodentate ligand has been reported for the asymmetric hydrogenation of enamides, although some monodentate P ligands were successfully used in the hydrogenation of dehydroamino acid derivatives. [6] Here we describe highly efficient monodentate chiral ligands 1 containing a 1,1 -spirobiindane backbone for the Rh-catalyzed asymmetric hydrogenation of -arylethenylamine derivatives [Eq. (1)] with excellent enantioselectivities (up to 99.7% ee).

The chiral ligands containing pyridinyl moieties and oxazolines bridged by disubstituted methylene 2-4 were prepared and they provided ee values 17-68% higher than unsubstituted analogues 1 in the palladium-catalyzed enantioselective allylic alkylation of 1,3-diphenyl-2-propenyl acetate with dimethyl malonate.

The dihydrodinaphthazepinyl-oxazoline ligands 3 have been synthesized and tested in the copper-catalyzed enantioselective cyclopropanation of olefins with diazoacetates. The ligands 3 were efficient in the cyclopropanations of styrene derivatives with up to 90% ee. The match of chiralities of binaphthyl and oxazoline in the ligands 3 is crucial for obtaining high enantioselectivity. The absolute configurations of cyclopropanation products were controlled mainly by the configuration of binaphthyl.

The design of new chiral ligands is the key in the development of transition metal catalyzed asymmetric synthesis.1 Many chiral diphosphine ligands have been prepared and applied in asymmetric catalytic reactions with excellent enantioselectivities. 1,2 Among the chiral diphosphine ligands that have been reported, the atropisomeric C2-symmetric phosphines with a biaryl scaffold initiated by Noyori and co-workers 3 with BINAP were found to have the widest application in the transition metal catalyzed reactions. 4 Planar chiral diphosphines based on ferrocene or paracyclophane backbones have also been applied to a number of reactions with a remarkable degree of success. 5 However, the spiro diphosphine compounds, another type of axially chiral ligands, have not been synthesized until now. 6 Recently, we designed chiral phosphoramidite ligands (SIPHOS) 7 containing a 1,1'-spirobiindane backbone and demonstrated that these ligands can be highly efficient for the Rh-catalyzed asymmetric hydrogenation of functionalized olefins. Especially, in the case of asymmetric hydrogenation of R-arylethenylamines, the spiro monophosphoramidite ligands provided a significantly higher level of enantiocontrol compared to that of the monophosphoramidite ligands derived from BINOL. 7b We now describe the synthesis of spiro diphosphines 6 (SDP) containing 1,1-spirobiindane as a new chiral scaffold and their application in the ruthenium-catalyzed asymmetric hydrogenation of simple ketones with high activity (S/C up to 100 000) and excellent enantioselectivity (ee up to 99.5%).