Methanol → 4-Amino-8-bromo-N-propylcinnoline-3-carboxamide

Participants

Reaction Conditions

Reaction Steps

A 22 L, 3-necked flask equipped with a mechanical stirrer, thermometer, nitrogen inlet, reflux condenser, and addition funnel was charged with N-propyl-2-cyano-2-[(2-bromophenyl)hydrazono]acetamide (195.4 g, 0.632 mol) in toluene (4 L). Aluminum chloride (295 g, 2.21 mol) was added in three portions. The mixture was heated with a mantle to 90° C. in approximately 30 minutes. After 2.5 hours, the heat was removed and the reaction mixture was allowed to cool to room temperature overnight. The reaction mixture was cooled in an ice bath to ≦10° C. and celite was added. Water (680 mL) was added dropwise over 1 hr at ≦10° C. After stirring for 30 minutes, methylene chloride was added (8 L). The reaction mixture was cooled to ≦10° C. and 10% sodium hydroxide (5.8 L) was added dropwise over 45 minutes at ≦10° C. After stirring for 30 minutes, tetrahydrofuran (2 L) was added and the phases were allowed to separate. The aqueous layer was removed, filtered through celite, and the filter cake washed with 2:1 methylene chloride:tetrahydrofuran (4 L). Note: Addition of fresh portions of methylene chloride helped expediate the rather tedious filtration. The phases of the filtrate were separated and the organic phase was transferred to a separatory funnel. Separation of the organic phase from the aqueous base as quickly as possible helped avoid undue hydrolysis of the propyl amide in the product. The solids remaining in the reaction flask were dissolved with 2:1 tetrahydrofuran:methanol (4 L) and then 10% methanol in chloroform (4 L). The layers were separated and the organic layer was washed with brine (500 mL), dried over magnesium sulfate, filtered, and concentrated under reduced pressure to a dark brown solid. The solid was slurried in diethyl ether, collected by filtration and dried. The crude solid (188 g) was then dissolved in hot methanol (6 L), treated with activated charcoal (19 g), stirred 15 minutes at reflux, filtered through celite while hot, concentrated to approximately 3 L, and allowed to crystallize overnight. The solids were collected, washed with diethyl ether (400 mL) and dried in a vacuum oven at 50° C. to give a white crystalline solid. The filtrate was concentrated to approximately 1 L and a second crop obtained. The mother liquors were stripped and a third and fourth crop were obtained from additional recrystallizations to afford a total of 164.6 g of the desired compound as a white crystalline solid (84%). 1H NMR (300.132 MHz, CDCl3) δ 8.57 (bs, 1H), 8.12 (dd, J=7.6, 1.1 Hz, 1H), 7.83 (dd, J=8.4, 1.0 Hz, 1H), 7.50 (dd, J=8.4, 7.5 Hz, 1H), 3.48 (q, J=6.7 Hz, 2H), 1.69 (sextet, J=7.3 Hz, 2H), 1.03 (t, J=7.4 Hz, 3H). MS APCI, m/z=309/311 (M+H). HPLC 1.66 min.

Provenance & Evidence