Kinetic Resolution of Racemic Mandelic Acid Esters by N,N′‐Dioxide–Scandium‐Complex‐Catalyzed Enantiomer‐Selective Acylation

Abstract

A simple and efficient acylative kinetic resolution of racemic mandelic acid esters was accomplished with a chiral N,N'-dioxide-scandium(III) complex under mild and base-free reaction conditions. A variety of mandelic acid esters performed well in the reaction, obtaining both acylated products (up to 49% yield, 97% ee) and recovered substrates (up to 49% yield, 95% ee) in high enantioselectivities with perfect selectivity factors (up to 247). The enantioselective recognition and catalytic models were also proposed for the catalytic KR reaction.

Direct Aerobic α-Hydroxylation of Arylacetates for the Synthesis of Mandelates

“…The residue was purified using a chromatography column on silica gel to afford product 2 . Compounds 2a – 2c , 2d , 2e , 2f , 2g – 2i , 2j , 2k , 2l , 2m , and 6 were known and the NMR data were identical to those previously reported.…”

“…Gradient elution was performed with ethyl acetate/petroleum ether (1/8–1/5); white solid, m.p. 91–93 °C, (lit: 90–92 °C); 59 mg; 81% yield. 1 H NMR (500 MHz, CDCl 3 ) δ ppm 7.49–7.39 (m, 2H), 7.39–7.28 (m, 6H), 7.20 (m, 2H), 5.24 (t, J = 15.0 Hz, 2H), 5.15 (d, J = 10.0 Hz, 1H), 3.48 (d, J = 5.0 Hz, 1H); 13 C­{ 1 H} NMR (125 MHz, CDCl 3 ) δ ppm 173.6, 138.3, 135.1, 128.7, 128.7, 128.6, 128.6, 128.1, 126.7, 77.4, 73.1, 67.8.…”