Substituent Effects On The Asymmetric Allylation Of Aldehydes

The asymmetric allylation of aldehydes is one of the most important methods for preparation of chiral homoallylic alcohol, which is the building block in organic synthesis of fine chemistry and drugs.Chiral homoallylic alcohol was prepared in this paper from asymmetric allylation of aldehyde with enantiomerically pure allylboronate tartramides such as chiral N,N'-diphenyl tartramide and N,N'-dibenzyl tartramide auxiliaries.In this paper the preparation of chiral auxiliaries was from chiral tartrate derivatives which was gained by D-(-)-tartaric acid reacted with amine. The chiral tartrate derivatives was then reacted with triallylborane to get chiral tartramide auxiliaries.The triallylborane was gained from allyl bromide-magnesium Grignard reacted with boron trifluoride diethyl etherate, and the Grignard reagent was synthesised freshly by allyl bromide with metal magnesium powder under nitrogen at 0-5℃.Aldehyde was reacted with chiral auxiliaries in low temperature and then quenched with basic solution, the outcome was then filtered to seperate solid from solution. The solid was chiral tartrate derivatives and it was reclaimed by recrystalization and the solvent for recrystalization was mixture of acetic acid and water. The yield of recrystalization can be more than 90%. It was concluded by experiment that the enantiomeric excess and yield of the outcome were almost no difference whenever use freshly made tartrate derivatives or not. So the tartrate derivates can be used many times like freshly made just by recrystalization. The filtrate was extracted with ether and then concentrated, our target outcome was separated by silica gel from the concentrated solution.In this paper, another three kind of amine were choosed to be reacted with tartrate acid to get tartrate derivatives. By comparing the results it was concluded that the enantiomeric excess can be the best when the auxiliaries was N,N'-diphenyl tartramide, and the e.e. of the asymmetric allylation was affected by electronattracting or donating effect of the substituent group of aldehyde and the yield was affected by water-solubility of the outcome.