Pienkos, J. A.; Knisely, A. T.; MacLeod, B. L.; Myers, J. T.; Shivokevich, P. J.; Teran, V.; Sabat, M.; Myers, W. H.; Harman, D. Double Protonation of Amino-Substituted Pyridine and Pyrimidine Tungsten Complexes: Friedel–Crafts-like Coupling to Aromatic Heterocycles. Organometallics 2014, 33, 5464-5469.
Abstract
2-(Dimethylamino)pyridine (2-DMAP) and 2-(dimethylamino)pyrimidine derivatives form η2-bound complexes with the dearomatization agent {TpW(NO)(PMe3)} that are each capable of undergoing a double protonation. In the case of 2-DMAP, the resulting π-allyl species reacts with the α-carbon of thiophene or 2-methylfuran, thereby coupling the heterocyclic rings. In the case of the thiophene-derived product, subsequent oxidative decomplexation using ceric ammonium nitrate affords a novel organic amidine derivative. Examples of tungsten-promoted acetylation and fluorination of the aminopyridine ring are also described.
