ASYMMETRIC ALLYLATION OF CARBONYL-COMPOUNDS WITH TARTRATE-MODIFIED CHIRAL ALLYLIC TIN REAGENTS

Chiral allylating reagents, readily generated in situ from tin(II) cat echolate [Sn-II(O2C6H4)], allyl halides, chiral dialkyl tartrates, and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), reacted smoothly with aldeh ydes or reactive ketones at -78 degrees C in the presence of a catalyt ic amount of copper salts to afford the corresponding optically active homoallyl alcohols. Allylation of aromatic aldehydes and pyruvates by the present chiral tin reagents proceeded in high yields (81-99%) wit h high enantioselectivities (89-94%ee). In addition, both enantiomers of dimethyl citramalate were prepared from the allylation products of benzyl pyruvate.