GOLD(I)-CATALYZED ASYMMETRIC ALDOL REACTIONS OF ISOCYANOACETIC ACID-DERIVATIVES WITH FLUOROARYL ALDEHYDES

The catalytic asymmetric synthesis of stereochemically defined nuoro-p henylserines is reported. In the title reaction, when methyl isocyanoa cetate is employed, the number of fluorine atoms in the phenyl ring of benzaldehyde controls stereochemical outcome of the reaction giving r ise in the case of monofluorobenzaldehydes corresponding trans-oxazoli nes with more than 90% of both trans-selectivity and % ee, while in th e case of polyfluorobenzaldehydes corresponding cis-oxazolines are for med as dominant isomers with high enantiomeric excess (up to 63% of ci s with 86-90% ee). In contrast to this, aldol reactions of isocyanoace tamide with fluoro-benzaldehydes provide dominant formation of trans-o xazolines (77-92% of trans with 80-94% ee) in all cases studied. The o bserved unusual stereodifferentiation in the reaction of methyl isocya noacetate with polyfluorobenzaldehydes is rationalized on the basis of an electron donor-acceptor type attractive interaction between the po lyfluorophenyl ring and the enolate oxygen.