Asymmetric conjugate additions to 1,1′-diactivated cyclic enones—a comparative study
2009; Elsevier BV; Volume: 20; Issue: 16 Linguagem: Inglês
10.1016/j.tetasy.2009.07.006
ISSN1362-511X
AutoresXiaoping Tang, Alexander J. Blake, William Lewis, Simon Woodward,
Tópico(s)Chemical Synthesis and Analysis
ResumoA study of copper-phosphoramidite-catalysed ZnR2 and AlR3 additions to 1,1′-dicarbonyl-activated cyclic Michael acceptors has revealed high enantioselectivities for AlR3 (R = Me, Et) 1,4-addition to a range of 3-acylcoumarins (85–98% ee, trans:cis ∼90:10) using commercial or readily available ligands. Large substituents at the 6-position, and to some extent at the 5-position, of the coumarin are less well tolerated, nor is truncation of the coumarin motif to a comparable 2-acylcyclohexenone (ee values up to 78%).
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