Ethylene Glycol → 5'-Bromo-7'-methoxyspiro[[1,3]dioxolane-2,3'-indolin]-2'-one

Participants

Reaction Steps

A stirred mixture of 5-bromo-7-methoxyindoline-2,3-dione (3.6 g, 14 mmol), p-TSA (1.14 g, 6 mmol) and toluene (100 mL) was refluxed using a Dean-Stark apparatus for 0.2 h. Ethylene glycol (9.3 g, 150 mmol, 10.7 eq.) was added and refluxed using a Dean-Stark apparatus for another 2 hours. The mixture was cooled and concentrated to 20 mL. EtOAc (100 mL) was added, washed with water (20 mL), brine (50 mL×2), dried over Na2SO4, filtered and concentrated under reduced pressure. Purified by column (CH2CL2/EtOAc=8:1) to give the desired product as a light brown solid (0.21 g, crude, 5%). 1H NMR (400 MHz, DMSO-d6): δH 10.66 (s, 1H), 7.48 (s, 1H), 7.26-7.27 (m, 1H), 7.13-7.14 (m, 1H), 4.25-4.31 (m, 4H), 3.86 (s, 3H). MS (ESI) m/e [M+1]+ 300/302.

Provenance & Evidence