Selenium Dioxide → HCID 21034922, compound

Participants

Reaction Steps

1-(3-methoxybenzyl)-6,7-dimethoxyisoquinoline-4-carboxylic acid ethyl ester (159 mg, 0.417 mmol, the intermediate in the preparation of [6,7-Dimethoxy-1-(3-methoxy-benzoyl)-isoquinolin-4-yl]-acetic acid) (Example 7) was dissolved into 4 ml of acetic acid. Then selenium dioxide (69.5 mg, 1.50 eq) was added. The mixture was refluxed for 20 minutes and then evaporated to dryness. The residue was suspended into ethyl acetate and the mixture was passed through a layer of silica gel. The filtrate was evaporated to give 1-(3-methoxybenzoyl)-6,7-dimethoxyisoquinoline-4-carboxylic acid ethyl ester as a solid (135 mg, 82%). This material (95.6 mg, 0.242 mmol) was suspended into 5 ml of methanol. Then 1N sodium hydroxide solution (0.5 ml) was added. The mixture was refluxed for 1 hr. TLS showed complete disappearance of the starting material. The mixture was evaporated and the residue was dissolved into 5 ml of water and then filtered. The filtrate was acidified with 1N hydrochloric acid to give 6,7-Dimethoxy-1-(3-methoxy-benzoyl)-isoquinoline-4-carboxylic acid as a solid (76 mg, 86%). ES-MS calculated for C20H17NO6 (m/e) 367.36, observed 368.4 (M+1). 1H-NMR is consistent with the desired structure.

Provenance & Evidence