p-Toluenesulfonyl azide → 2-Diazo-3-oxobutyroxyethyl methacrylate

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2-Diazo-3-oxobutyroxyethyl methacrylate was prepared according to the protocol described in Y. K. Rao et al., Indian J. Chem., 25B, 735 (1986). A mixture of 2-acetoacetoxyethyl methacrylate (4.28 g, 20 mmol, available from Eastman Chemical, Kingsport, Tenn.), dichloromethane (30 mL), and p-toluenesulfonyl azide (3.94 grams, 20 mmol) was cooled to 0° C. and then DBU (1,8-diazabicyclo[5.4.0]undec-7-ene, 4.48 mL, 30 mmol) was added dropwise. After the addition of DBU, the reaction mixture was stirred at room temperature for 15 minutes and then poured into a mixture of 10% KOH (100 mL) and diethyl ether (50 mL). The organic layer was separated and the aqueous layer was re-extracted with diethyl ether (50 mL). The organic extracts were combined and then washed sequentially with 3N HCl (50 mL), deionized water (2×50 mL) and saturated aqueous sodium chloride solution (50 mL). The organic layer was dried using anhydrous magnesium sulfate, filtered, and concentrated to give 4.39 grams of 2-diazo-3-oxobutyroxyethyl methacrylate as a pale yellow oil. 1H NMR (400 MHz, CDCl3): δ 1.94 (s, 3H); 2.47 (s, 3H); 4.35-4.55 (m, 4H); 5.60 (s, 1H); 6.12 (s, 1H). IR: 2181 cm-1. Decomposition temperature: 156° C. (by DSC).

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