Efficient Intramolecular General-Acid Catalysis of the Reactions of α-Effect Nucleophiles and Ammonia Oxide with a Phosphate Triester

The SN2(P) reactions with α-effect nucleophiles of the cationic form 1·H+ of phosphate triester diethyl 8-(N,N-dimethylamino)-1-naphthyl phosphate are catalyzed by the neighboring dimethylammonium group, with accelerations as high as 106. Hydroxylamine and its N-methyl and N,N-dimethyl derivatives, which react through oxygen, we presume by way of the zwitterionic ammonia oxide tautomers, are of special interest. The α-effect and the efficient general-acid catalysis in this system are mutually reinforcing. The α-effect is greater for the reactions of the triester than for the corresponding mono- and diesters and qualitatively different for hydroxylamines RR′NOH, where the likely role of the ammonia oxide tautomer NH3+−O− is evaluated by ab initio calculations. The initial phosphorus-containing product NH2OPO(OEt)2 reacts further with hydroxylamine to generate diethyl phosphate and diimide, identified by its disproportionation to hydrazine and N2 and its reducing potential.