Efficient intramolecular general-acid catalysis of the reactions of alpha-effect nucleophiles and ammonia oxide with a phosphate triester.

ABSTRACT

The S(N)2(P) reactions with alpha-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 10(6). 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 alpha-effect and the efficient general-acid catalysis in this system are mutually reinforcing. The alpha-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 NH(3)(+)-O(-) is evaluated by ab initio calculations. The initial phosphorus-containing product NH(2)OPO(OEt)(2) reacts further with hydroxylamine to generate diethyl phosphate and diimide, identified by its disproportionation to hydrazine and N(2) and its reducing potential.