(S)-2-[2-(Diphenylphosphino)phenyl]-4-phenyloxazoline

(1; R = Ph) [148461-15-8] C27H22NOP (MW 407.47) (2; R = i-Pr) [148461-14-7] C24H24NOP (MW 373.46) (3; R = t-Bu) [148461-16-9] C25H26NOP (MW 387.49) (readily available chiral ligands for enantiocontrol of palladium-catalyzed allylic substitution reactions1, 2) Physical Data: 1 amorphous solid; [α]D +30.8° (c = 1.0, CHCl3). 2 amorphous solid; [α]D −44.9° (c = 1.4, CHCl3). 3 mp 105 °C; [α]D 58.2° (c = 1.2, CHCl3). Solubility: insol H2O; sol most organic solvents. Preparative Methods: chiral phosphinoaryloxazolines, a class of ligands developed independently in three different laboratories,1, 3, 4 are readily prepared in enantiomerically pure form starting from chiral amino alcohols and aromatic carboxylic acids or nitriles. Several short, convenient syntheses from 2-bromobenzonitrile (eq 1),1, 5 2-bromobenzoic acid (eq 2),3 or 2-fluorobenzonitrile (eq 3)4 have been described. Alternatively, derivatives such as 2, which do not contain any reactive groups in the oxazoline ring that are attacked by BuLi, can be prepared from aryloxazolines by orthometalation and subsequent reaction with Ph2PCl (eq 4).1 Phosphino-oxazolines with an additional stereogenic center at the phosphorus atom, such as 4, and phosphinomethyl oxazolines of type 5 have also been reported.3 The different synthetic routes allow for a wide range of structural modifications at the oxazoline ring, the phosphine group, and the ligand backbone. (1) (2) (3) (4) Purification: impurities such as phosphine oxides, formed by air oxidation, can be removed by column chromatography on silica gel or, for crystalline derivatives, by recrystallization. Handling, Storage, and Precautions: Phosphino oxazolines of this type are sufficiently stable to be handled in air. For longer periods of time, they should be stored at −20 °C under argon.