Asymmetric hydroarsination reactions toward synthesis of alcohol functionalised C-chiral As-P ligands promoted by chiral cyclometallated complexes

The asymmetric hydroarsination reactions between diphenylarsine and 3-diphenylphosphanyl-but-3-en-1-ol and 2-diphenylphosphanyl-prop-2-en-1-ol have been achieved using the organopalladium complex containing ortho-metallated (R)-[1-(dimethylamino)ethylnaphthalene as the chiral reaction template in high stereoselectivities under mild conditions. Hydroarsination of 3-diphenylphosphanyl-but-3-en-1-ol with diphenylarsine generated only one stereoisomer as five-membered As-P bidentate chelate on chiral naphthylamine palladium template. Using the same chiral metal template, similar hydroarsination reaction was carried out on 2-diphenylphosphanyl-prop-2-en-1-ol which gave two different products in the ratio of 2.6 to 1. The major isomer was identified as the expected five-membered As-P bidentate ligand and the minor isomer was identified as the elimination product. The naphthylamine auxiliary could be removed chemoselectively by treatment with concentrated hydrochloric acid. Optically pure As-P ligands containing the hydroxy groups at the chiral carbon centres were prepared by ligand displacement. The absolute configuration and coordination properties of the complexes have been established by single crystal X-ray analysis. (C) 2011 Elsevier B.V. All rights reserved.