Towards the Diastereoselective Functionalization of Non-Racemic Acetal Derivatives of η6-Arylcarbonyl Complexes of Tricarbonylchromium

Abstract

(S)-Butane-1,2,4-triol (2) has been investigated as a potential chiral auxiliary for the formation of non-racemic acetals derived from η⁶-arylcarbonyl complexes of tricarbonylchromium. Predominantly the cis dioxan (5) was formed from benzaldehyde, leading to preparation of the η⁶-Cr(CO)₃ complex (16), and of the derived complexes (23) and (24). Lithiation{electrophile quenching of these complexes gave a mixture of products arising fromortho and benzylic functionalization. Reaction of acetophenone, or of the η⁶-Cr(CO)₃ complexes (45) or (46), with either the triol (2) or its tris(silyl) ether (15) under conditions of kinetic or thermodynamic control gave an inseparable mixture of acetals.