154775-55-0Relevant academic research and scientific papers
Stereochemistry of the methoxide induced rearrangement of an α-bromophosphonamidate: Cleavage of the P-N and P-C bonds in the azaphosphiridine oxide intermediate
Harger, Martin J. P.,Sreedharan-Menon, Ramesh
, p. 527 - 532 (1997)
Menthyl P-(bromomethyl)-N-tert-butylphosphonamidate 5 has been prepared from (1R,2S,5R)-(-)-menthol and the SP diastereoisomer has been isolated. This rearranges with methoxide [Me3(PhCH2)N+ MeO- in THF-MeOH] to give only the SP diastereoisomer of menthyl methyl (tert-butylamino)-methylphosphonate 6 and very largely (95%) the SP diastereoisomer of menthyl methyl N-tert-butyl-N-methylphosphoramidate 7. The configurations of these products show that when the (postulated) azaphosphiridine oxide intermediate 16 suffers ring opening by methoxide, the P-N bond is cleaved (to give 6) with inversion of configuration but the P-C bond is cleaved (to give 7) with predominant retention. These contrasting stereochemistries suggest that nucleophilic attack on the P=O group of the azaphosphiridine oxide generates a five-coordinate intermediate (not merely a transition state) that exists long enough to undergo pseudorotation.
