Preparation from Methyl Allophanate

The reaction mixture is chilled to 0° in an ice-salt bath, and 2.9 g. of biurea (m.p. 245 to 246°) is filtered off. The filtrate is evaporated on a hot-water bath under reduced pressure (water aspirator) until a solid cake remains in the flask. The reaction cake is broken up and washed with 95% ethanol to give 110 g. (83%) of crude hydrazine urazolate (m.p. 195 to 196° with decomposition). The product can be purified with 86% recovery by dissolving it in hot water (2.5 ml./g.), filtering through a warm funnel, adding 95% ethanol to turbidity, and chilling. 

The 110 g. of hydrazine urazolate and 1 1. of acetone are placed in a 2-1. three-necked standard-taper flask equipped with a stirrer and reflux condenser. The suspension is stirred and heated for 2 hours, after which the mixture is chilled and the insoluble product removed by filtration. The product is washed well with acetone and finally air-dried. The product weighs 78 g. and melts at 244 to 246° with decomposition. This represents a 94% con- 

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Allophanyl hydrazide has been prepared previously as the hydrochloride by the zinc-hydrochloric acid reduction of 1-nitrobiuret.1 The new procedure2,3 outlined here entails the hydrazinolysis of allophanic esters in alcoholic solution. Excellent yields (80 to 84%) of allophanyl hydrazide are obtainable with a minimum of difficulty using readily available starting materials. The methyl and ethyl allophanates are prepared from urea and the corresponding chlorocarbonic esters.4... 

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