Allylic C–H Oxidation•Amination Catalyst “White Catalyst”

1,2-Bis(phenylsulfinyl)ethane palladium(II) diacetate (1) is a palladium catalyst, which was developed by M. C. White et al., and named “White catalyst” after the developer. For an example of its characteristic reactivity differing from other homogeneous palladium catalysts, the allylic C–H oxidation reaction has been reported, in which an acetoxy group is introduced regioselectively into the allylic position.¹⁾

Moreover, White et al. have also reported the macrolactonization reaction of ortho-substituted salicylic acid substrates, applying the reaction into intramolecular allylic C–H oxidation, in which the corresponding 14-membered ring macrolides (6 and 7) are obtained in moderate yields.²⁾

In addition, White et al. have reported the allylic C–H amination reaction which transforms N-tosylcarbamate (8) into oxazolidinone (9). This reaction affords anti-isomer 9 with diastereoselectivity, which allows it to provide the syn-1,2-amino alcohol (10).³⁾

Typical Procedure: Synthesis of macrolactone 7²⁾
A 1 dram vial is charged with 1 (10.1 mg, 0.02 mmol). Another 1 dram vial is charged with the benzoic acid (84.1 mg, 0.2 mmol). To a 100 mL round bottle flask is charged benzoquinone (43.2 mg, 0.4 mmol), 1 (transferred using 10 mL CH₂Cl₂), and the acid substrate (transferred using 10 mL CH₂Cl₂). The flask is charged with a stir bar, topped with a condenser, and allowed to heat at 45 °C with an empty balloon on the top of the flask. After 72 h, the reaction is quenched with saturated NH₄Cl (5 mL) and extracted with CH₂Cl₂ (2 x 30 mL). The combined organic layers are washed with H₂O (1 x 30 mL), dried over MgSO₄, filtered and concentrated in vacuo to give a yellow solid. After lactonization, the amount of remaining starting material can not be determined by crude ¹H-NMR due to overlap of the product and starting material peaks (a small amount of starting material does remain). Purification by SiO₂ flash chromatography (10%EtOAc/hexanes) provides the desired product as a white solid (44.0 mg, Y. 54%).