title: Synthesis of aminopyridines and aminopyridones by cobalt-catalyzed [2+2+2] cycloadditions involving yne-ynamides: scope, limitations, and mechanistic insights.
abstract: An in-depth study of the cobalt-catalyzed [2+2+2] cycloaddition between yne-ynamides and nitriles to afford aminopyridines has been carried out. About 30 nitriles exhibiting a broad range of steric demand and electronic properties have been evaluated, some of which open new perspectives in metal-catalyzed arene formation. In particular, the use of [CpCo(CO)(dmfu)] (dmfu=dimethyl fumarate) as a precatalyst made possible the incorporation of electron-deficient nitriles into the pyridine core. Modification of the substitution pattern at the yne-ynamide allows the regioselectivity to be switched toward 3- or 4-aminopyridines. Application of this synthetic methodology to the construction of the aminopyridone framework using a yne-ynamide and an isocyanate was also briefly examined. DFT computations suggest that 3-aminopyridines are formed by formal [4+2] cycloaddition between the nitrile and the intermediate cobaltacyclopentadiene, whereas 4-aminopyridines arise from an insertion pathway.
authors.affiliation: UPMC, Univ Paris 06, IPCM 7201, 4 Place Jussieu, 75252 Paris Cedex 05, France.
authors.forename: Pierre
authors.initials: P
authors.lastname: Garcia
authors.forename: Yannick
authors.initials: Y
authors.lastname: Evanno
authors.forename: Pascal
authors.initials: P
authors.lastname: George
authors.forename: Mireille
authors.initials: M
authors.lastname: Sevrin
authors.forename: Gino
authors.initials: G
authors.lastname: Ricci
authors.forename: Max
authors.initials: M
authors.lastname: Malacria
authors.forename: Corinne
authors.initials: C
authors.lastname: Aubert
authors.forename: Vincent
authors.initials: V
authors.lastname: Gandon
mesh_terms: D000480:Alkynes / Q000737:chemistry*; D000577:Amides / Q000737:chemistry*; D000631:Aminopyridines / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D003035:Cobalt / Q000737:chemistry*; D003500:Cyclization; D015394:Molecular Structure; D009570:Nitriles / Q000737:chemistry*; D011728:Pyridones / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D000480:Alkynes; D000577:Amides; D000631:Aminopyridines; D009570:Nitriles; D011728:Pyridones; D003035:Cobalt