Palladium-Catalyzed Synthesis of Amidines via tert-Butyl isocyanide Insertion

Pálinkás, Noémi and Kollár, László and Kégl, Tamás (2018) Palladium-Catalyzed Synthesis of Amidines via tert-Butyl isocyanide Insertion. ACS OMEGA, 3. pp. 16118-16126. ISSN 2470-1343

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Abstract

Para-substituted iodobenzenes were reacted with tert-butyl isocyanide and piperidine as nucleophiles in the presence of palladium−diphosphine catalysts. Both single and double insertion of the isocyanide was observed and the corresponding amidines and etimine−amidines were obtained in yields of practical interest. With the increase of the tert-butyl isocyanide/iodobenzene ratio, 100% chemoselectivity toward the ketimine−amidine was achieved. The formation of the products was rationalized on the basis of a catalytic cycle analogous to that of the minocarbonylation reactions. Clear connection was found between the activity and the electronic structure of the proposed catalyst Pd(diphosphine) by computational studies, as the more negative partial charge on palladium resulted in higher conversion. Among five isocyanide substrates, only tert-butyl isocyanide was proved to be active.

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