The synthesis of spirobitetraline phosphoramidite ligands and their application in rhodium-catalyzed asymmetric hydrogenation

A racemic 1,1'-spirobitetralin-8,8'-diol (SBITOL) was conveniently synthesized from 3-methoxybenzaldehyde in 26 % yield over 9 steps and resolved via its bis-(S)-camphorsulfonates. The corresponding chiral spirobitetraline monophosphoramidite ligands have been prepared and their rhodium complexes were applied in the asymmetric hydrogenation of dehydroamino esters with good to excellent enantioselectivities (up to 99.3 % ee).