Synthesis and structure of cyclic phosphate, phosphoramidate, phosphonates, and phosphonium salts. Phosphatrane formation

Reaction of 'tris(2-hydroxy-3,5-dimethylbenzyl)amine (6) with phosphorus re agents led to the formation of the phosphoramidate, N[CH2(Me2C6H2)O](2)PO ( 1), the phosphate N[CH2(Me2C6H2)O](2)[CH2(Me2C6H2)OH]P(O)(OPh) (2), the pho sphonium salts N[CH2(Me2C6H2)O](3)PMe+I- (3A) and N[CH2(Me2C6H2)O](3)PMe+I3 - (3B), and the phosphonates N[CH2(Me2C6H2)O](2) [CH2(Me2C6H2)OH]P(O)Me (4) and N[CH2(Me2C6H2)O](2)[CH2(Me2C6H2)-OSiMe3]P(O)Me (5). X-ray analysis pro vided molecular structures for all of the compounds. The solid-state struct ural representations were supported in solution by an analysis of the NCH2 proton NMR patterns. The structures of 3A and 3B show the presence of phosp hatranes with weak P-N donor interactions. These represent the first phosph atranes containing all six-membered rings. Variable temperature analysis of the H-1 NMR spectra of 3A indicates fluxional behavior whereby a racemic m ixture of the chiral phosphonium salt rapidly intraconverts at room tempera ture. The activation energy for the enantiomeric conversion of the clockwis e and anticlockwise orientations of the propeller-like phosphatrane is 11.2 kcal/mol, which is compared to that of the isoelectronic silatrane N[CH2(M e2C6H2)O](3)SiMe (E), 10.3 kcal/mol.