Ammonium Hydrogen Phosphoramidate

Ammonium hydrogen phosphoramidate (11.4 g., 0.1 mole) is dissolved in 20 ml. of 50% potassium hydroxide solution and warmed to 50-60° for 10 minutes to expel ammonia. The solution is cooled to 5-10°, neutralized to pH 6 (Alkacid test paper) with glacial acetic acid, and treated with 1 1. of ethanol to precipitate the potassium salt which is filtered with suction, washed successively with alcohol and ether, and air-dried. Yield is 8.1 g. (60%). Anal. Calcd. for KHP03NH2 N, 10.37 P, 22.93. Found N, 10.4 P, 22.7. 

Ammonium hydrogen phosphoramidate forms colorless monoclinic crystals that appear to be orthorhombic. The powder x-ray diffraction2 and infrared absorption3 data have been reported. The salt is stable and nonhygroscopic, is moderately soluble in water, and melts at 233-234°. 

In contrast to some related reviews, which use reaction class or electrophiles as organizational elements, this chapter is divided into three main sections according to catalyst class (i) Bronsted acid catalysis by phosphoric acid and phosphoramide derivatives, (ii) N—H hydrogen bond catalysis by organic base and ammonium systems, and (iii) combined acid catalysis including Bronsted-acid-assisted Bronsted acid, Lewis-acid-assisted Bronsted acid, and Lewis-acid-assisted Br0nsted acid systems (Figure 5.1). 

One of the two hydrogen atoms of phosphoramidates can be temporarily blocked with a trimethylsilyl group. The sodium salt of diethyl V-(trimethylsilyl)phosphoramidate (102) reacted with alkyl bromides in benzene in the presence of 10 mol % of tetra-n-butylammonium bromide to afford, after desilylation, the corresponding V-alkyl derivatives (103) in 79-95% yields for primary alkyl halides. Secondary alkyl halides gave poor results (Scheme 43). The addition of the quaternary ammonium salt is essential to promote the alkylation reaction. Hexamethyldisilazane and its cyclic analogs can also be utilized in the preparation of amines under moderate conditions (Scheme 43). ... 

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