Synthesis, characterisation and reactivity studies of chiral ß-diketiminate-like supported aluminium Lewis acid complexes towards difficult Diels Alder cycloadditions.
Dalton Trans
; 52(13): 4063-4076, 2023 Mar 28.
Article
em En
| MEDLINE
| ID: mdl-36880570
ABSTRACT
Synthesis and characterisation of several chiral, oxazoline containing ß-diketiminate type ligand supported-aluminium compounds are reported. Together with 1 equiv. of Na(BArCl4) (ArCl = 3,5-Cl2-C6H3), these chiral Lewis acid complexes, which possess an "achiral end" and "chiral end" have been successfully utilised as catalysts in asymmetric Diels-Alder reactions of 1,3-cyclohexadiene and several different chalcones. Systematic increase in the steric demand of the ligand's "achiral end" of these complexes resulted in enhanced enantioinduction for the cyclisation of 1,3-cyclohexadiene and chalcone. Further structural modifications of the "chiral end" clearly established that having a tert-butyl group connected to the stereogenic centre of the oxazoline fragment yielded the highest enantioselectivity value for the examined cyclisation. A substrate scope was then expanded using several different dienophiles (i.e. chalcones) generating an enantiomeric excess range of 24-68%.
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MEDLINE
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En
Ano de publicação:
2023
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Article