Pyridine → Methyl 6,7-dimethoxy-2-methyl-4-oxo-1,2,3,4-tetrahydroquinoline-1-carboxylate

A mixture of 1.2 g. (5.45 mmol) of the quinoline product of Example 4, 792 mg. (10.7 mmol) of dry pyridine and 5.5 ml. of methylene chloride was stirred and cooled by an ice-water bath while 758 mg. (8.02 mmol) of methyl chloroformate in 1 ml. of methylene chloride was added over a 10 min. period at a rate to maintain a 10°-15° C. temperature. The ice bath was removed and the reaction allowed to stir at room temperature for 45 min. then poured onto 25 ml. of saturated sodium bicarbonate solution. The methylene chloride layer was separated and washed with 25 ml. saturated sodium bicarbonate solution and saturated sodium chloride solution, then dried over magnesium sulfate, and gravity filtered and evaporated to a yellow solid. The solid was triturated with 5 ml. anhydrous ether, filtered, and washed with minimum ether, then air dried to 1.1 g. of a yellow solid, m.p. 156°-158°. This material was dissolved in 10 ml. of hot ethyl acetate, treated with 50 mg. Darco G60, filtered and crystallized by the addition of hexane to give 727 mg. of an off-white solid, m.p. 159°-160° after drying in vacuum at 100° C (1 mm) for 24 hrs.