The activity and enantiocontrol ability of the chiral catalysts prepared from spiro diphosphine ligands, SDP, and rhodium precursor were investigated in the asymmetric catalytic Pauson-Khand reaction. The results showed that SDP ligands were very effective in Rh-catalyzed Pauson-Khand reaction, and their complexes with rhodium could convert a variety of 1,6-enyne compounds into bicyclopentone derivatives under CO atmosphere in high yields with good enantioselectivities. The SbF 6 − was found to be a suitable counter anion of the catalyst, and 1,2-dichloroethane was the best choice of the solvent for Pauson-Khand reaction.Transition-metal-catalyzed Pauson-Khand reaction (PKR) [1][2][3][4] can conveniently convert an alkyne, an alkene and a carbon monoxide into cyclopentenone compounds in one step, which widely exist in natural products and bioactive molecules [5,6] . Owing to the wide application in organic synthesis, the Pauson-Khand reaction was extensively studied and a number of catalysts have been developed. Besides cobalt [1][2][3][4] , which was originally used, many other transition metals were applied to catalyze Pauson-Khand reaction [7][8][9][10][11][12][13] . Recently, the asymmetric catalytic version of this reaction has also been realized. The complexes of Ti [14][15][16] , Co [17][18][19] , Ir [20] and Rh [21][22][23] with chiral ligands could serve as catalysts in the enantioselective Pauson-Khand reaction. However, except for the Ti catalyst [(S,S)-(EBTHI)Ti(CO) 2 ], all the catalysts that gave high degree of enantiocontrol contained BINAP and its derivatives as chiral ligands. It is of great interest to find new efficient catalysts that use other types of chiral ligands for asymmetric Pauson-Khand reaction.Recently, a new type of C 2 symmetric diphosphine ligands SDP with a chiral 1,1′ -spirobiindane scaffold have been developed in our laboratory (Scheme 1). The Ru(II) complexes of SDP ligands were proven to be highly efficient for asymmetric hydrogenation of simple ketones (S/C up to 100,000 and ee up to 99.5%) [24] . The Pd(II) complexes of SDP were also excellent catalysts for asymmetric allylic alkylation reactions [25] . During the course of our study on the application of SDP ligands, we became interested in the asymmetric Pauson-Khand reaction. In this paper, we would like to report our results in the investigation on the Rh-catalyzed Pauson-Khand reaction using SDP ligands.
Experimental
Apparatus and reagentsAll reactions and manipulations were performed 82 Science in China: Series B Chemistry Scheme 1. SDP ligands.under argon or carbon monoxide using standard Schlenk technique. Anhydrous THF, DME, toluene and dioxane were distilled from sodium benzophenone ketyl. DCE and EtOAc were distilled from calcium hydride prior to use. The substrates 1a [7] , 1c [22] , 1d [22] , 1h [16] , 1i [26] , 1j [27] and 1k [26] were prepared by the literature methods. Melting points were measured on an RY-Ι apparatus and uncorrected. 1 H and 13 C NMR spectra were recorded on Brucker 300 MHz. Chemical shifts...