Group 7-12 transition-metal complexes serve as effective catalysts for the regioselective intramolecular hydroamination of aminoalkynes having the general formula RCtC(CH 2 ) n -NH 2 (n ) 3, R ) H, Ph; n ) 4, R ) H) and of 2-(phenylethynyl)aniline. Primary products are pyrrolidines and piperidines bearing an R-alkylidene functionality and 2-phenylindole, respectively. Isomerization yields the corresponding pyrrolines and 1,2-dehydropiperidines. The catalytic properties of the transition-metal complexes depend on the appropriate choice of ligand, solvent, temperature, and counteranion. Principles for identifying the most active transition-metal catalysts for the hydroamination of alkynes and for optimizing the reaction conditions are developed. The X-ray crystal structure of one catalyst, [PdCl(triphos)](CF 3 -SO 3 ), has been determined.

Condensation of aromatic acyl compounds with N,Ndimethylformamide diethyl acetal in a pressure tube under microwave heating gives 1-aryl-3-dimethylaminoprop-2-enones in almost quantitative yields. In the presence of hydrazine, these intermediates are transferred to the corresponding 3-arylpyrazoles.

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Because of the electron‐donating effects of their terminal dimethylamino groups, the carbonyl units of 1‐aryl‐3‐(dimethylamino)prop‐2‐en‐1‐ones are excellent proton acceptors. Intra‐ and intermolecular hydrogen bonds formed by these species were investigated by structural techniques (X‐ray and neutron diffraction), spectroscopy, and density functional calculations. Co‐crystallization of a derivative bearing three (dimethylamino)prop‐2‐en‐1‐one units attached at one center in the presence of different proton donors produced one‐ and two‐dimensional H‐bridged polymers. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

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