[reaction: see text] An original TiCl(4)/t-BuNH(2)-mediated hydroamination/annulation domino reaction of delta-keto-acetylenes is described. The synthesis of pyrrolo[1,2-a]indole-2-carbaldehydes, starting from 2-carbonyl-1-propargyl-1H-indoles runs under mild reaction conditions. A conceivable mechanism is also discussed. TiCl(4) has proved to be an effective multiactivity reagent: catalyst/Lewis acid/water scavenger. Some unpublished 2-carbonyl-1-propargyl-1H-indoles are prepared by means of Suzuki- and Negishi-type reactions.

A palladium-mediated multicomponent domino reaction leading to 2-aryl-4-amino-quinolines and 2-aryl-4-amino[1,8]naphthyridines is reported. The scope of the reaction was examined using carbon monoxide, two 2-ethynyl-arylamines, four aryl iodides, and 10 primary amines as substrates. The selection of the appropriate catalytic system was achieved testing several palladium/phosphine systems and overrides previously reported drawbacks associated with the use of primary amines in related reactions. Moreover several features concerning the role of both palladium [(0) and (II)] and phosphines are reported.

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Ready accessible 2-trifluoromethanesulfonyloxyindole-1-carboxylic acid ethyl ester undergoes palladium-catalyzed coupling reactions with different partners giving rise to 2-aryl, heteroaryl, vinyl, allyl, and alkynyl indoles in good to excellent yields.

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)