Hammett studies of enantiocontrol by PHOX ligands in Pd-catalyzed allylic substitution reactions.
Electronically modified PHOX ligands 3a-e were synthesized to probe the mechanism of the enantioselective palladium-catalyzed allylic alkylation and amination reactions. Alkylation with dimethyl sodiomalonate produced only a small variation in the ee (89.3% to 93.4%), but amination with benzylamine gave a much wider variation in the ee (16.4% to 66.6%). Hammett analysis suggests that the substituents interact more significantly with phosphorus and supports a combined electronic and steric basis for enantioselection. [reaction: see text]
Constantine
Ryan N
RN
Department of Chemistry and Biochemistry, Middlebury College, Middlebury, VT 05753, USA.
Kim
Naomi
N
Bunt
Richard C
RC