17.85 g (90.98 mmol) of 4-methoxybenzyl carbazate was dissolved in 50 mL of CH2Cl2 in a 250 mL flask and then cooled in ice water. 21.42 g (155 mmol) of potassium carbonate dissolved in 80 mL of water was added. While the reaction mixture was being stirred in the ice bath, 17.0 g (79.95 mmol) of 5-methyl-2,3-dihydro-benzo[1,4]dioxine-6-carbonyl chloride in 60 mL of CH2Cl2 were slowly added. The reaction mixture was stirred at room temperature overnight and then transferred to a separatory funnel with 200 mL of CH2Cl2 and 200 mL of H2O. After shaking, a floating white precipitate was filtered off, washed with water, dried in a vacuum oven to give 29.1 g of N′-(5-methyl-2,3-dihydro-benzo[1,4]dioxine-6-carbonyl)hydrazinecarboxylic acid 4-methoxy-benzyl ester. The CH2Cl2 solution was dried and concentrated to give 5.19 g of a residue consisting of the original acid chloride, 4-methoxybenzyl carbazate, and some product. TLC Rf=0.38 (streak 1:1 ethyl acetate:hexane). 1H NMR (CDCl3, 300 MHz) δ (ppm): 7.4-6.7 (m, 6H), 5.139 (s, 2H), 4.279 (s, 4H), 3.81 (s, 3H), 2.303 (s, 3H).
