p-Toluenesulfonic acid → 2-(4-Bromophenyl)chroman-4-one

Participants

Reaction Steps

Prepared according to general procedure using E-tert-butyl 3-(4-bromophenyl)-2-(2-hydroxyphenylcarbonyl)prop-2-enoate (81.0 mg, 0.20 mmol), thiourea catalyst III (14 mg, 0.020 mmol) in 2.0 mL toluene for 38 h at −25° C. and p-toluenesulfonic acid (19 mg, 0.10 mmol) for 36 h. Purification via column chromatography with 10% EtOAc/hexanes afforded 39.5 mg (65%) of 8 as a white solid in 92% ee. mp=115-116° C. [α]D: +50.4 (EtOH, c=0.5). Analytical data for 8: IR (film) 1691.8, 1604.8, 1465.1, 1304.6, 1222.9 cm−1; 1H NMR (500 MHz, CDCl3) δ 7.93 (d, J=7.5 Hz, 1H), 7.58-7.36 (AA′BB′, 4H), 7.52 (t, J=8.0 Hz, 1H), 7.09-7.05 (m, 2H), 5.45 (dd, J=13.2, 2.4 Hz, 1H), 3.00 (dd, J=16.8, 13.3 Hz, 1H), 2.88 (dd, J=16.8, 2.6 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ 191.7, 161.5, 138.0, 136.6, 132.3, 128.1, 127.3, 123.0, 122.1, 121.1, 118.3, 79.1, 44.8; LRMS (electrospray): Exact mass calcd for C15H11BrO2 [M]+, 301.99, 303.99. Found [M+1], 305.5.

Provenance & Evidence