Phosphorodiamidic chlorides

General preparative procedures for the preparation of A -alkyl phos-phoramidic dichlorides (10) and A TV -dialkyl phosphorodiamidic chlorides (11) from the appropriate amine and phosphoryl chloride have been described. With weakly basic amines, pyrophosphoryl chloride was... 

The phosphorodiamidic chloride thus obtained was then fluorinated. For example, diphenylphosphorodiamidic chloride was readily fluorinated by heating it with potassium fluoride in benzene, POCl(NHPh)2 + KF - POF(NHPh), + KCl. 

A,A-Bis(2-oxo-3-oxazolidinyl)phosphorodiamidic chloride (BOP-Cl, 64) has been found to be an efficient macrolactamization reagent [69]. Tatsuta and coworkers [69c] used it in the synthesis of the ansamycin antibiotic rifamycin W 123). As shown in Scheme 41, amino acid 121 was cyclized to 122 using 4 equiv of BOP-Cl and 10 equiv of diisopropylethylamine in toluene at 85 °C for 3 h. Upon deprotection and oxidation 123 was obtained in 30% yield from 121. 

Carboxamides were prepared from acids and amines in the presence of Af,Af -bis(2-oxo-3-oxazolidinyl)phosphorodiamidic chloride (311) and a tertiary base (84S413). In the first step, an ester (e.g., 313) was formed, which then reacted with amines to give carboxamides. In this way, optically active amide 315 was prepared in 74% yield from 3,3-dimethylacrylic acid (312) and optically active a-methylbenzylamine (314) in the presence of 311 and DBU in dimethylacetamide. 

Generally, phenyl iV-phenylphosphoramidochloridate and other very similar related organophosphorus reagents e.g. phosphorus oxychloride, phenyl dichlorophosphate, diphenylchlorophos-phate and iV,W -bis(2-oxo-3-oxazolinyl)phosphorodiamidic chloride have been utilised in recent years not only to form symmetrical carboxylic acid anhydrides but also in esterification and thiol esterification reactions although phenyl N-phenylphosphoramidochloridate is not so efficient for the latter two reactions compared to its analogs but is probably the best choice for forming the anhydride. ... 

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