Diphenyl phosphorochloridate, selective

Replacement of the two chlorine atoms with bulkier substituents produces an even more selective phosphorylating agent. For example, under reaction conditions in which phosphorus oxychloride gives product mixtures (pyridine solvent), diphenyl phosphorochloridate and di(2-terf-butylphenyl) phosphorochloridate will give approximately 90% and 100% phosphorylation at the primary hydroxyl, respectively ... 

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