Diels-Alder reactions scandium trifluoromethanesulfonate

Kitazume and Zulfiqar have investigated the aza-Diels-Alder reaction in 1,8-diazabicyclo[5,4,0]-7-undecenium trifluoromethanesulfonate [EtDBU][OTf] [184] (Fig. 5.2-5). This reaction involved the scandium(iii) trifluoromethanesulfonate catalyzed reaction of an imine (usually generated in situ from an aldehyde and an amine) with a diene. An example of this reaction is given in Scheme 5.2-74. The yields in this reaction were high (80-99%) and it was found that the ionic liquid could be recycled and reused. 

The use of a scandium trifluoromethanesulfonate catalyst has also been reported for aza-Diels-Alder reactions. The reaction of benzaldehyde and amine 104 in [emim][OTf] as the ionic liquid led to the in situ formation of the corresponding imine. Cycloaddition of this imine with Danishefsky s diene gave the A -aryl-6-phenyl-5,6-dihydro-4-pyridone 105 in a quantitative yield (Scheme 44). 

Kobayashi, S. Hachiya, L Araki, M. Ishitani, H., Scandium trifluoromethanesulfonate (Sc(OTf)3). A novel reusable catalyst in the Diels-Alder reaction. Tetrahedron Lett, 1993, 34,3755-8. 

RS Oakes, TJ HeppenstaU, N Shezad, AA Clifford, CM Rayner. Use of scandium tris(trifluoromethanesulfonate) as a Lewis acid catalyst in supercritical carbon dioxide efficient Diels-Alder reactions and pressure dependent enhancement of endo exo stereoselectivity. Chem Commun 1459-1460, 1999. 

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