X=Y-ZH COMPOUNDS AS POTENTIAL 1,3-DIPOLES .29. THE IMINIUM ION ROUTE TO AZOMETHINE YLIDES - REACTION OF CYCLIC SECONDARY-AMINES WITH MONO-FUNCTIONAL AND BI-FUNCTIONAL ALDEHYDES

1,2,3,4-Tetrahydro-isoquinoline and -β-carboline react with a range of mono- and bi- functional aldehydes to give azomethine ylides. The anti-dipole is formed stereospecifically or, in the case of benzaldehyde and 2-methylbenzaldehyde, stereoselectively. The effect of the structure of the aldehyde on the stereochemistry of the derived azomethine ylide is rationalised in terms of steric and electronic effects. Inter- and intra-molecular trapping of the azomethine ylides gives cycloadducts in good yield. © 1990.