The synthesis of 3‐substituted 1‐methylpyrrolo[1,2‐a]pyrazines and 3‐substituted isoquinolines was achieved by the intramolecular cyclisation of 2‐acetyl‐1‐propargylpyrroles and 2‐alkynylbenzaldehydes, respectively, in the presence of ammonia under microwave heating. The tandem imination/annulation of 2‐alkynylbenzaldehydes was easily accomplished under standard conditions, while TiCl4 was used to achieve pyrrolo[1,2‐a]pyrazines. The reaction mechanism and the regioselectivity were discussed on the basis of theoretical calculations and spectroscopic data. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Abstract2‐Acyl‐N‐propargylindoles 1 and 2‐acyl‐3‐propargylindoles 5 undergo aminobenzannulation reactions with pyrrolidine in the presence of an appropriate Lewis acid to give 9‐aminopyrido[1,2‐a]indoles 6 and 1‐aminocarbazoles 7, respectively. The selection of the appropriate Lewis acid, TiCl4 or GaCl3 for 1 and InCl3 for 5, allows the domino process involving the initial formation of an enamine intermediate, followed by a regioselective 6‐exo‐dig intramolecular nucleophilic attack of the nucleophilic terminus of the unsaturated system (the β‐carbon of the enamino moiety) to the carbon–carbon triple bond. Moreover, several features concerning the reaction mechanism and the role of both catalysts, in connection with the electronic properties of the reacting alkynes, are reported. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

The synthesis of diastereoisomeric 3,4‐disubstituted 1,2,3,4‐tetrahydrocarbazoles by Diels–Alder cycloaddition reactions between [(E)‐2‐vinyl]indole‐1‐carboxylic acid ethyl esters and open‐chain C=C dienophiles is reported and discussed. The reactions proceed with high regioselectivity whereas the diastereoselectivity ranges from moderate to excellent depending on the substitution pattern on both the dienes and dienophiles and on the catalyst employed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

The gold‐catalyzed intermolecular Diels–Alder cycloaddition and competitive Michael addition reactions between 2‐vinylindoles and enones/enals are reported. The reaction outcome strictly correlates with the electronic character of the heteroaromatic substrate. Thus, Diels–Alder cycloadducts are the sole products in the presence of less electron‐rich heterocycles, whereas Michael addition adducts are observed with more electron‐rich heterocycles. Plausible competitive reaction mechanisms are proposed and discussed as well.

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