Catalytic Asymmetric Induction with Chiral Thioureas

1 Catalytic Asymmetric Induction with Chiral Thioureas 

Ar = 4-NO2C6H4, 2-NO2C6H4, 3-NO2C6H4, 4-CF3C6H4, 4-CIC6H4.2,4-a2C6H3,4-BrCeH4 CeHs, 2-Furyl 

R = Ph, 2-MePh, 2-BrPh, 2-EPh, 3-MePh, 4-MePh, 4-BrPh, 4-CIPh, 4-N02Ph. 4-CNPh, 4-MeOPh, 3-CIPh,/ Pr. 

2 Caitalytic Asymmetric Induction with Proline Derivatives 

p-Me-C6H4, o-MeO-C6H4, p-MeO-C6H4, 3,5-CF3 C0H3, /BU-C0H4, y -(C0H.. )-C0H4, /7-pent, 1-(yclohexenyl, 

152a R=CsH5 152b R = 4-MeOC6H4 NHR 152c R=4-CIC6H4 

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Chiral thioureas have been synthesized and used as ligands for the asymmetric hydroformylation of styrene catalyzed by rhodium(I) complexes. The best results were obtained with /V-phenyl-TV -OS )-(l-phenylethyl)thiourea associated with a cationic rhodium(I) precursor, and asymmetric induction of 40% was then achieved.387,388 Chiral polyether-phosphite ligands derived from (5)-binaphthol were prepared and combined with [Rh(cod)2]BF4. These systems showed high activity, chemo- and regio-selectivity for the catalytic enantioselective hydroformylation of styrene in thermoregulated phase-transfer conditions. Ee values of up to 25% were obtained and recycling was possible without loss of enantioselectivity.389... 

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