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

Noémi Pálinkás; László Kollár; Tamás Kégl

doi:10.1021/acsomega.8b02010

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

ACS Omega. 2018 Nov 28;3(11):16118-16126. doi: 10.1021/acsomega.8b02010. eCollection 2018 Nov 30.

Authors

Noémi Pálinkás¹, László Kollár^{1

2}, Tamás Kégl^{1

2}

Affiliations

¹ Department of Inorganic Chemistry, University of Pécs and Szentágothai Research Centre, P. O. Box 266, H-7624 Pécs, Hungary.
² MTA-PTE Research Group for Selective Chemical Syntheses, Ifjúság u. 6., H-7624 Pécs, Hungary.

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 ketimine-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 aminocarbonylation 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.