Precursor of the Chiral Hypervalent Iodine Catalyst

(R,R)-2-Iodo-1,3-bis[1-(mesitylcarbamoyl)ethoxy]benzene (1), which was developed by Ishihara et al., is a precursor of the chiral hypervalent iodine catalyst, and its utility for the enantioselective intramolecular oxidative coupling reaction (Kita Spirolactonization) has been reported. The chiral hypervalent iodine(III) species, which is generated in situ from 1 and mCPBA as a co-oxidant, catalyzes the enantioselective spirolactonization of 1-naphthol derivatives 2 to afford the corresponding spirolactones 3 with high enantioselectivities. This reaction is environmentally benign because it does not have to use any toxic metal reagents. Since spirolactones are used as pharmaceutical intermediates, it is expected to be applied to pharmaceutical synthesis.

Typical Procedure^1b) :
A solution of 2a (R=H) (216 mg, 1.0 mmol), 1 (92.2 mg, 0.15 mmol, 15 mol%) and mCPBA (269 mg, 1.2 mmol, 1.2 eq.) in CHCl₃ (50 mL) is stirred at 0 °C. After 18 h, the resulting mixture is poured into aqueous Na₂S₂O₃ (20 mL) and aqueous NaHCO₃, and extracted with CHCl₃ (2 times). The organic layers are dried over anhydrous MgSO₄ and solvents are removed in vacuo. The residue is purified by flash column chromatography on silica gel (hexane-EtOAc = 10:1 to 4:1) to give 3a (129 mg, 0.6 mmol) in 60% yield (92%ee).