Preparation of aryl(dimethyl)aluminum reagents and their in situ use in NHC-Cu-catalyzed ECA reactions with trisubstituted enones to generate all-carbon quaternary stereogenic centers

March 08, 2024

• Title:       

  Preparation of aryl(dimethyl)aluminum reagents and their in situ use in NHC-Cu-catalyzed ECA reactions with trisubstituted enones to generate all-carbon quaternary stereogenic centers

• Image Source:

  Enantioselective synthesis of quaternary carbon stereogenic centers through copper-catalyzed conjugate additions of aryl- and alkylaluminum reagents to acyclic trisubstituted enones

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  Scheme 2

• Associated context:

  A range of trisubstituted enones and in situ generated aryl(dialkyl)aluminum reagents can be used (Table 1). Reaction involving 2-thienyl-substituted 2c (vs. 3-substituted 2a,  Scheme 2) with Ph(Me)2Al leads to 73% conversion in 12 h  (entry 1), and 3b is isolated in 57% yield with complete transfer of the phenyl unit in 92:8 e.r. Formation of the sterically demanding stereogenic center that contains two aryl groups is relatively sluggish when one bears an ortho unit; the example in entry 2 is illustrative (17% conv. with the derived ortho chlorophyll substrate).