| Abstract
| - Mechanistic details of the hydroamination of alkynes were studied using the palladium-catalyzed cyclization of 6-aminohex-1-yne to 2-methyl-1,2-dehydropiperidine as specific example. One intermediate palladium species was observed by in situ 31P NMR spectroscopy and identified as the product of a nucleophilic attack of the nitrogen lone pair on a coordinated alkyne group.
- Mechanistic details and limiting factors for the palladium-catalyzed addition of aminesto alkynes (hydroamination) were studied, using the cyclization of 6-aminohex-1-yne to2-methyl-1,2-dehydropiperidine as a specific example. The complex [Pd(Triphos)](CF3SO3)2showed the highest catalytic activity of a series of structurally and electronically distinctpalladium complexes. Several methods, such as calorimetry and in situ IR and NMRspectroscopy, were used to obtain evidence for a possible reaction cycle. It seems likely that(i) the substrate initially coordinates via the amine group and (ii) an intermediate is formedwhich is the product of a nucleophilic attack of the amine on a coordinated alkyne. Additionof an acid to the reaction mixture led to a strong increase in the reaction rate, probably byaccelerating protolytic cleavage of the palladium−carbon bond in the intermediate complex.
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