Asymmetric Friedel-Crafts reactions, pyrrole

Most recently, a dual catalytic Friedel-Crafts reaction that merges organocatalysis and transition metal catalysis for the asymmetric synthesis of annulated pyrroles has been achieved. 

In this work, the combination of cinchona-alkaloid-derived primary amine and Au(I) phosphine complex has been employed to effect two consecutive Friedel-Crafts-type reactions of pyrrole in one pot to furnish 2,3-annulated pyrroles containing a seven-membered ring (eq 1) This reaction proceeds through initial asymmetric 1,4-addition of p)rrole to enones catalyzed by the primary amine followed by an intramolecular 7-c/ido-dig cycliza-tion catalyzed by the Au(I) phosphine complex. 

The first organocatalytic asymmetric carbon nucleophilic addition to enals was reported by MacMillan in 2001 [15]. MacMillan reported the first Friedel-Craft alkylation between N-substituted pyrroles and enals promoted by catalyst 7. The reaction renders the final compounds in good yields and enantioselectivities (Scheme 33.4). 

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