SYNTHESIS, 918 (1982)

Diethyl N-Alkylphosphoramidates; General Procedure:

A mixture of diethyl phosphoramidate (9.2 g, 60 mmol), dry 
mercury(II) nitrate (6.67 g, 20 mmol), the alkene (20 mmol), and 
1,1-dichloroethane (60 ml) is refluxed gently with stirring for 
4 h. The resultant yellow-orange solution is cooled to 0 C and 
then aqueous 10% sodium hydroxide (60 ml), and a solution of 
sodium borohydride (0.8 g, 20 mmol) in aqueous 10% sodium 
hydroxide (20 ml) are added. Stirring is continued for 1 h at 
room temperature. The precipitated mercury is filtered off and
washed with dichloromethane (30 ml). The organic layer is 
thoroughly washed with water (3 x 20 ml), dried with magnesium
sulfate, and evaporated. The residual crude phosphoramidates 
mostly are analytically pure when heated at 40-50 C/0.2 torr 
for 1 h to remove traces of volatile impurities.

10 mmol of the crude phosphoramidate is left to stand overnight 
in 30 ml of benzene saturated with dry HCl gas. The benzene and 
excess HCl is evaporated and the residue is added a solution of 
40 g of NaOH in 50 ml of water and the liberated amine is 
steam-distilled. The distillate is made alkaline (pH: 12-14), 
saturated with solid sodium chloride, and extracted with ether 
(3 x 50 ml). The extract is dried with magnesium sulfate, 
saturated with gaseous hydrogen chloride. Evaporation to dryness 
followed by addition of hexane (10 ml) affords crude amines 
(70% yield for amphetamine) which can be recrystallised if 
necessary.

CHEMICALS

Diethyl phosphoramidate, was obtained from diethyl phosphite 
(cheap) and gaseous ammonia (cheap cheap) in tetrachloromethane 
according to the known procedure (J. Chem. Soc. (1945) 660)

Mercury(II) Nitrate: Commercial mercury (II) nitrate hemihydrate, 
strongly hygroscopic and containing varying amounts of water, is 
ground in a mortar and dried in vaccuo over phosphorus pentoxide 
for several days. The dry material is stored over phosphorus 
pentoxide... (Hey! Look! Anhydrous mercuric nitrate! No oven!)

