Sieber JD, * Chennamadhavuni D, Fandrick KR, Qu B, Han ZS, Savoie J, Ma S, Samankumara LP, Grinberg N, Lee H, Song JJ, Senanayake CH. Boehringer Ingelheim Phamaceuticals, Ridgefield, USA
Development of New P-Chiral P,π-Dihydrobenzooxaphosphole Hybrid Ligands for Asymmetric Catalysis.
Org. Lett. 2014;
16: 5494-5497
Key words
P-chiral hybrid ligands - rhodium - boronic acids
Significance
A new family of P-chiral P,π-hybrid ligands has been synthesized from a chiral dihydrobenzooxaphosphole core (Z. S. Han et al. J. Am. Chem. Soc. 2013, 135, 2474). These newly developed ligands show a very high level of enantiocontrol in the rhodium-catalyzed addition of aryl boronic acids to tosyl imines.
Comment
The synthesis of the ligands with strong electron-withdrawing substituents (like CF3) failed by the alkylation with cinnamyl derivatives, alternatively an allylation and subsequent metathesis strategy was employed. Steric and electronic properties were controlled easily by varying the substituents on the phosphorus atom and on the π-system.
