Enantioselective Synthesis, Structure, and Application of an ortho-Sulfinyl Arylboronic Acid

Despite their potential use as catalysts and reagents, few chiral arylboronic acids are known, especially those with a proximal stereogenic ortho-substituent. Herein, the design, synthesis, structural study, and preliminary application of optically enriched ortho-sulfinyl arylboronic acids is described. These compounds were prepared in 90% enantiomeric excess by way of electrophilic trapping of lithiobenzene with the optically enriched reagent, tert-butyl tert-butanethiosulfinate, followed by a sulfoxide-directed ortho-lithiation/borylation. The resulting products were found to exist in the open boronic acid form, and they show promise as direct amidation catalysts and as resolving agents for the analysis of enantiomeric purity of chiral diols.