title: Spiroketal-based phosphorus ligands for highly regioselective hydroformylation of terminal and internal olefins.
abstract: A new class of bidentate phosphoramidite ligands, based on a spiroketal backbone, has been developed for the rhodium-catalyzed hydroformylation reactions. A range of short- and long-chain olefins, were found amenable to the protocol, affording high catalytic activity and excellent regioselectivity for the linear aldehydes. Under the optimized reaction conditions, a turnover number (TON) of up to 2.3×10(4) and linear to branched ratio (l/b) of up to 174.4 were obtained in the Rh(I)-catalyzed hydroformylation of terminal olefins. Remarkably, the catalysts were also found to be efficient in the isomerization-hydroformylation of some internal olefins, to regioselectively afford the linear aldehydes with TON values of up to 2.0×10(4) and l/b ratios in the range of 23.4-30.6. X-ray crystallographic analysis revealed the cis coordination of the ligand in the precatalyst [Rh(3d)(acac)], whereas NMR and IR studies on the catalytically active hydride complex [HRh(CO)(2)(3d)] suggested an eq-eq coordination of the ligand in the species.
authors.affiliation: State Key Laboratory of Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, 18 Tianshui Middle Road, Lanzhou 730000, P.R. China.
authors.forename: Xiaofei
authors.initials: X
authors.lastname: Jia
authors.forename: Zheng
authors.initials: Z
authors.lastname: Wang
authors.forename: Chungu
authors.initials: C
authors.lastname: Xia
authors.forename: Kuiling
authors.initials: K
authors.lastname: Ding