K. Yamada et al., ASYMMETRIC ALLYLATION OF CARBONYL-COMPOUNDS WITH TARTRATE-MODIFIED CHIRAL ALLYLIC TIN REAGENTS, Bulletin of the Chemical Society of Japan, 70(9), 1997, pp. 2301-2308
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.