A chiral 1,2-bisphospholane ligand with a novel structural motif: applications in highly enantioselective Rh-catalyzed hydrogenations.

The design and synthesis of chiral phosphane ligands have played a significant role in the development of efficient transition metal catalyzed reactions. Catalytic asymmetric hydrogenation, as one of the most practical and efficient methods for the synthesis of chiral building blocks, has attracted much attention in both academia and industry.[1] Although excellent enantioselectivities have been obtained by using chiral bisphosphane ligands such as DIPAMP,[2] DIOP,[3] Chiraphos,[4] Norphos,[5] BPPM,[6] DEGphos,[7] BINAP,[8] DuPhos,[9] BPE,[9] BICP,[10] SpirOP,[11] PennPhos,[12] BisP*,[13] MiniPhOS,[14] Binaphane,[15] and PHANEPHOS,[16] the search for more practical and efficient ligands in terms of ease of preparation, high enantioselectivity, and high turnover number (TON) remains an important goal in asymmetric hydrogenation. Herein we report the synthesis and application of a new chiral 1,2-bisphospholane ligand, (1S,1S ,2R,2R )-1,1 -di-tert-butyl-[2,2 ]-diphospholanyl (1; abbreviated (1S,1S ,2R,2R )-TangPhos, Figure 1) in highly effi-