Monoselective o-C-H Functionalizations of Mandelic Acid and α-Phenylglycine

摘要

Pd-catalyzed C-H functionalization of mandelic acid and α-Phenylglycine is reported. We have developed different protocols for the arylation, iodination, acetoxylation, and olefination of these substrates based on two different (Pd(Ⅱ)/Pd(Ⅳ) and Pd(Ⅱ)/Pd(0)) catalytic cycles. Four crucial features of these protocols are advantageous for practical applications. First, the α-hydroxyl and amino groups are protected with simple protecting groups such as acetates (Ac, Piv) and carbamates (Boc, Fmoc), respectively. Second, these protocols do not involve installation and removal of a directing group. Third, monoselectivity is accomplished. Fourth, no epimerization occurs at the vulnerable α-chiral centers.