Diffusion-ordered NMR spectroscopy (DOSY) studies of mixed alkali metal cation hexamethyldisilazide bases

ORGN 166

Deyu Li, Deyu_Li@Brown.edu, Jia Liu, and Paul G Williard. Department of Chemistry, Brown University, 324 Brook Street, Box H, Providence, RI 02912
The enhanced deprotonating ability of mixed organoalkali bases containing lithium and sodium or potassium over those lithium only bases was first discovered by Wittig. Despite the wide applications of “superbasic reagents” in syntheses, relatively few physical organic studies of these species have been reported. Diffusion-ordered NMR spectroscopy (DOSY) is a powerful tool in determining solution structures of mixed aggregates. The Li(HMDS)-K(HMDS), Li(HMDS)-Na(HMDS) and Na(HMDS)-K(HMDS) complexes were investigated by DOSY and other NMR experiments like 1H-7Li HMBC and 6Li spectroscopy. We anticipate that studies of mixed alkali metal cation HMDS bases will provide structure-reactivity basis of this synthetically useful class of reactive intermediates.