Synthesis of Amidines by Palladium-Mediated CO2 Extrusion Followed by Insertion of Carbodiimides: Translating Mechanistic Studies to Develop a One-Pot Method

Abstract

A palladium-mediated one-pot synthesis of amidines from aromatic carboxylic acids and carbodiimides (RNCNR) is reported as an isoelectronic adaption of CO 2 ExIn (ExIn = Extrusion-Insertion) reactions developed for the synthesis of thioamides from carboxylic acids and isothiocyanates (RNCS). Multistage mass spectrometry (MS n ) experiments for model systems established "proof of concept", demonstrating decarboxylation of [(L)Pd(O 2 CAr)] + (L = 1,10-phenanthroline or py), to give [(L)PdAr] + , followed by reaction with a carbodiimide, RNCNR, to yield [(L)Pd(NRC(NR)Ar)] + (R = isopropyl). DFT calculations predicted these reactions as highly exothermic and occurring via carbodiimide insertion ..