C2-symmetric bis-thioglycosides as new ligands for palladium-catalyzed allylic substitutions

A new divergent design for the synthesis of optically pure bis-thioglycoside type I is reported. In only two steps a common chiral intermediate with up to eight free alcohols: two primary and six secondary is obtained. From this common intermediate a large number of ligands can be synthesized. A positional scanning like strategy has permitted the rapid discovery of an efficient catalyst for the palladium-catalyzed asymmetric allylation of malonate. Dynamic NMR spectroscopy of a Pd(II) complex has shown that there is an efficient stereochemical control of the sulfur configuration upon coordination to the palladium. (C) 2003 Elsevier Science Ltd. All rights reserved.