- Aza Diels-Alder reaction
The Aza Diels-Alder reaction converts
imine s anddiene s totetrahydropyridine s. Thisorganic reaction is a modification of theDiels-Alder reaction . The nitrogen atom can be part of thediene or thedienophile .The imine is often generated
in situ from anamine andformaldehyde . An example is the reaction ofcyclopentadiene withbenzylamine to an azanorbornene . ["N-benzyl-2-azanorbornene" Paul A. Grieco and Scott D. LarsenOrganic Syntheses , Coll. Vol. 8, p.31; Vol. 68, p.206 [http://www.orgsyn.org/orgsyn/prep.asp?prep=cv8p0031 Article] ]In the
enantioselective Diels-Alder (DA) reaction of ananiline ,formaldehyde and acyclohexenone catalyzed by (S)-proline even the diene is masked. ["Direct Catalytic Enantioselective Aza-Diels-Alder Reactions" Henrik Sundén, Ismail Ibrahem, Lars Eriksson, Armando CórdovaAngewandte Chemie International Edition 4877 2005 [http://www3.interscience.wiley.com/cgi-bin/abstract/110546882/ABSTRACT Abstract] ]The
catalytic cycle starts with the reactions of the aromatic amine withformaldehyde to theimine and the reaction of theketone withproline to the diene. The second step, anendo trig cyclisation , is driven to one of the two possibleenantiomer s (99% ee) because the imine nitrogen atom forms ahydrogen bond with thecarboxylic acid group of proline on theSi face . Hydrolysis of the final complex releases the product and regenerates the catalyst.References
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