Abstract
AbstractGold‐catalyzed reactions of pyrrole derivatives with methyl vinyl ketone preferentially give rise to doubly substituted products, with an excess of methyl vinyl ketone even triple substitutions can be observed. This is independent of the electronic nature of substituents on the pyrrole ring, even substrates with electron‐withdrawing acyl substituents in 1‐, 2‐ or 3‐position show this behavior. The NH group of the pyrrole ring may be unprotected, no competing hydroamination is observed. In an intramolecular competition experiment with a furan ring only the pyrrole ring reacted. The constitutions of the highly‐substituted pyrroles were proven by NMR spectroscopy and one X‐ray structure analysis. Control experiments show that Yb(OTf)3 does not catalyze these reactions, but Ag+ and H+ does. Contrary to pyrroles, under similar reaction conditions indoles show a clean monosubstitution reaction. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
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