Asymmetric Aerobic Oxidation of α-Hydroxy Acid Derivatives by
<i>C</i><sub>4</sub>-Symmetric, Vanadate-Centered, Tetrakisvanadyl(V) Clusters
Derived from <i>N</i>-Salicylidene-α-aminocarboxylates
Chien-Tien Chen
Sampada Bettigeri
Shiue-Shien Weng
Vijay D. Pawar
Ya-Hui Lin
Cheng-Yuan Liu
Way-Zen Lee
10.1021/jo070575f.s005
https://acs.figshare.com/articles/journal_contribution/Asymmetric_Aerobic_Oxidation_of_Hydroxy_Acid_Derivatives_by_i_C_i_sub_4_sub_Symmetric_Vanadate_Centered_Tetrakisvanadyl_V_Clusters_Derived_from_i_N_i_Salicylidene_aminocarboxylates/2978464
A series of chiral vanadyl(V) methoxides bearing 3-<i>t</i>-butyl-5-substituted <i>N</i>-salicylene-l-valinate and l-<i>t</i>-leucinate as chiral auxiliaries has been prepared. In all cases except the 3,5-di-<i>t</i>-butyl analogue, they
exist as monomers both in solution and in the single crystal state. In the case of the 3,5-di-<i>t</i>-butyl analogue,
the architectural nature of the vanadyl(V) complex highly depends on the base used during the complex
formation event. A pentanuclear <i>C</i><sub>4</sub>-symmetric complex was formed when potassium salts were employed
instead of the corresponding sodium salts. A central vanadate(V) unit serves to grip four identical chiral
monomeric vanadyl(V) units together, by which a potassium ion sits on top of the four flanking units
through carbonyl coordinations and serves to hold the whole cluster by cooperation with the central
vanadate(V) unit. In comparison with the corresponding monomeric vanadyl(V) methoxide complex, the
cluster complex was utilized to facilitate the asymmetric aerobic oxidations of various racemic
α-hydroxyesters, -amides, and -thioesters with excellent selectivity factors (<i>k</i><sub>rel</sub> 40 to >500).
2007-10-26 00:00:00
di
methoxide
chiral
pentanuclear C 4
Asymmetric Aerobic Oxidation
k rel 40
vanadyl
potassium
cluster
monomeric
vanadate
butyl analogue