2878
Concerning the experimental procedure,10 a slow addition of the starting aryl di- or trichloride (over a
period of 30 min for 20 mmoles) is crucial to the success of the arylamination process in order to minimise
the formation of 4. It is also noteworthy that aryl polychlorides possess a considerably enhanced activity
compared to arylchlorides.7 Indeed, aryl dichlorides and trichlorides were immediately consumed (<5
min) leading to mixtures of products 1 and 2 (5 and 6, respectively). Reactions involving an electron
poor aryl group were clearly faster than reactions involving an electron rich aryl group. All the reactions
starting from meta substituted dichlorides were completed in less than 3 h.
This enhanced reactivity prompted us to perform control experiments in order to demonstrate that the
reaction process is actually Ni-catalysed. Non-catalysed reactions between aryl dichloride (20 mmol) and
morpholine (80 mmol) were conducted in the presence of NaH (50 mmol) and t-AmONa (8 mmol) in
refluxing THF for 24 h. Dichlorobenzenes and 3,5-dichloropyridine afforded less than 10% of 1 by an
aryne type mechanism. On the other hand, in the absence of Ni catalyst, 2,6-dichloropyridine yielded a
mixture of compounds 1, 2 and 3 in, respectively, 35, 45 and 18% yield by a SNAr mechanism.
In summary, 2,20-bipyridine liganded nickel catalysed amination of aryl di- and trichlorides under
mild conditions. The efficiency of our protocol associated to the low cost of all reagents allowed the
large scale synthesis of new di- and triaminobenzenes. We are currently exploring the different aspects
of this methodology in order to extend its scope to the synthesis of aminated dendrimers potentially
displaying redox properties.
Acknowledgements
The authors wish to thank M. Reibel Bernard for his perfect technical assistance.
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