New Chiral Ligands Derived from Mandelic Acid: Synthesis and Application in the Asymmetric Phenyl Transfer Reaction to an Aromatic Aldehyde

Abstract

Starting from inexpensive enantiopure (R)- and (S)-mandelic acid, a range of α-hydroxy-2-oxazolines has been prepared. The synthesis involves the condensation of the acid chloride with a vicinal amino alcohol, followed by intramolecular cyclization to form the oxazoline ring. The resulting compounds have been used as ligands in the asymmetric phenyl transfer reaction to 4-chlorobenzaldehyde, employing a mixture of triphenylborane and diethylzinc as the phenyl source. Good yields (up to 76%) and moderate enantioselectivities (up to 35%) have been achieved.

Key words

asymmetric catalysis - mandelic acid - organometallics - oxazolines - phenyl transfer - zinc

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Rudolph, J.; Schmidt, F.; Bolm, C. Adv. Synth. Catal., accepted for publication.