Methane → 6,9-Difluorobenzo[g]isoquinoline-5,10-dione

Participants

Reaction Conditions

Reaction Steps

A solution of the mixture of 4-(2',5'-difluorobenzoyl) nicotinic acid and 3-(2',5'-difluorobenzoyl)isonicotinic acid (120 g, 0.456 mol) in fuming 20% H2SO4 (180 mL) was heated to 140° C. After about 30 minutes, more fuming 20% sulfuric acid (120 mL) was added to the hot reaction mixture in four portions of 30 mL each, every 20 minutes. Twenty minutes after the last addition the reaction mixture was cooled at about 80° C. and then was poured onto iced demineralized water (3000 g of ice and 3000 mL of water). The pH of the quenched reaction mixture was adjusted to 1 with 40% NaOH (850 mL) and the formation of a yellow-brown precipitate was observed. After about 1 hour at 0°-5° C. the crude precipitate was filtered and dried under vacuum to give crude 6,9-difluorobenzo[g]isoquinoline-5,10-dione (98.5 g). The reaction crude was dissolved in boiling THF (1000 mL) and the hot solution was decolored with active charcoal (9 g), filtered and concentrated to a volume of about 300 mL. After cooling at 0°-5° C. for about 2 hours a yellow solid was collected by filtration to afford analytically pure 6,9-difluorobenzo[g]isoquinoline-5,10-dione (90.6 g, 81% yield).

Provenance & Evidence