A convenient method for the preparation of alkyl dihydrogen phosphates was investigated. 2-Chloro-methyl-4-nitrophenyl phosphorodichloridate (2), a phosphorylating agent having a new protecting group, was prepared from 2-chloromethyl-4-nitrophenol (1) and phosphoryl chloride. It reacts smoothly with alcohols in the presence of tertiary amines to give the corresponding alkyl 2-chloromethyl-4-nitrophenyl phosphorochloridates (3), which were in turn converted by hydrolysis into alkyl 2-chloromethyl-4-nitrophenyl hydrogen phosphates (4). When the phosphates 4 are treated with pyridine, they change to inner salts of 1-(2ʹ-alkyl hydrogen phosphoroxy-5ʹ-nitrobenzyl)pyridinium hydroxide (7). The inner salts 7 readily underwent hydrolysis to yield the corresponding alkyl dihydrogen phosphates (8) and inner salt of 1-(2ʹ-hydroxy-5ʹ-nitrobenzyl)pyridinium hydroxide (9) in good yields. © 1969, American Chemical Society. All rights reserved.
