Equilibrium constants and alkylation kinetics of two lithium enolates/LiHMDS mixed aggregates in THF.

Mixed aggregates between lithium enolates and lithium hexamethyldisilazide (LIHMDS) have been studied in THF using UV-vis spectroscopy. The equilibrium constants (K-agg) between monomeric LiEn and monomeric LIHMDS are 760 and 560 M-1 when LiEn are LiSIBP and LiBnPAT, respectively. The alkylation kinetics of the reactions with benzyl bromide were studied at 25 C. The rate constants for the mixed aggregates, k(Mixed), are substantially smaller than those of the monomeric enolates.