A. t-Butyl hydrazodiformate. A solution of 28.6 g. (0.2 mole) of t-butyl azidoformate² and 26.4 g. (0.2 mole) of t-butyl carbazate³ in 60 ml. of pyridine (Note 1) is allowed to stand at room temperature for 1 week and is then diluted with 500 ml. of water. The snow-white microcrystalline powder that separates is removed by filtration and is washed with two 50-ml. portions of water. The yield of air-dried hydrazide, m.p. 124–126°, is 35.5–37 g. (77–80%). The product is pure enough for most applications but may be purified by recrystallization from a 1:1 mixture of benzene and ligroin (60–90°) from which it separates as small white needles, m.p. 124–125.5°. The recovery is 92%.

B. t-Butyl azodiformate. In a 500-ml. Erlenmeyer flask is placed a solution of 23.2 g. (0.1 mole) of crude t-butyl hydrazodiformate (m.p. 124–126°) in 175 ml. of methylene chloride and 7.9 g. (0.1 mole) of pyridine (Note 1). The solution is cooled by a stream of running tap water while 18.2 g. (0.102 mole) (Note 2) of N-bromosuccinimide (Note 1) is added during 6–7 minutes with swirling. The resulting solution is allowed to stand at room temperature for 5 minutes and is washed with two 100-ml. portions of water followed by one 100-ml. portion of 10% sodium hydroxide. The solution is dried for 30 minutes over magnesium sulfate, filtered into a large evaporating dish, and allowed to evaporate. The yellow-orange crystalline residue, m.p. 90–91.5°, which amounts to 20.7–21.8 g. (90–94.5%), is recrystallized by covering the dry solid with 35–40 ml. of petroleum ether (b.p. 30–60°) and adding ligroin (b.p. 60–90°) to the boiling solution until the solid dissolves. t-Butyl azodiformate, 19.8–20.0 g., m.p. 90.7–92°, separates from the cooled solution as large lemon-yellow crystals. Evaporation of the filtrate gives an additional amount of yellow solid which is recrystallized as before, yielding 0.4–0.7 g. of pure material, m.p. 90–92°. The total yield is 20.2–20.7 g. (88–90%).