O-ALLYLHYDROXYLAMINE HYDROCHLORIDE

Preparation

To a solution of 86.8 gm (1.55 moles) of potassium hydroxide in 330 ml of absolute ethanol is added a solution of 159 gm (1.52 moles) of ethyl N-hydroxycarbamate in 330 ml of absolute ethanol. With external cooling to maintain an internal temperature of 25°C to this mixture is added 195.5 gm (1.62 moles) of allyl bromide. After the addition has been com­pleted, the mixture is heated under reflux for 2 hr. After separating the potassium bromide formed during the reaction and washing it with abso­lute alcohol, the alcoholic solution is evaporated under reduced pressure. The residue is dissolved in ether and then the ether solution is extracted repeatedly with 10% aqueous sodium hydroxide solution. [From the ether solution, on evaporation 25.5 gm (18%) of ethyl N,O-diallylhydroxycar-bamate, b.p. 91-92°C (8.55 mm Hg) may be isolated.] The aqueous ex­tract is acidified with 10% aqueous sulfuric acid and the ethyl O-allylhy-droxycarbamate is extracted with ether. Upon evaporating the ether off, 134.2 gm (61%) of the intermediate product, b.p. 107°C (12.5 mm Hg), is isolated.
In a steam distillation apparatus, 134 gm of ethyl O-allylhydroxy-carbamate is treated with a solution of 120 gm of potassium hydroxide in 280 ml of water. The product is steam-distilled into a receiver containing dilute hydrochloric acid.
The steam distillate is evaporated under reduced pressure. The residue is taken up twice in absolute ethanol and dried by evaporation under re­duced pressure. The yield is 91 gm (55%, overall), m.p. 169-170°C. Upon recrystallization from absolute alcohol and dry ether, the melting point is raised to 170.6-170.8°C (172-174°C). Free O-allylhydrox-ylamine has the following reported properties: b.p. 98-99°C, n²⁵_D 1.4300.
The problems connected with the preparation of O-arylhydroxylamines by this method have been attributed to the instability of the aryl- substituted aminooxy group to the hydrolytic system used in its prepara­tion. This problem has recently been circumvented by substituting for ethyl N-hydroxycarbamate, t-butyl N-hydroxycarbamate.