Synthesis of aminopyridines and aminopyridones by cobalt-catalyzed [2+2+2] cycloadditions involving yne-ynamides: scope, limitations, and mechanistic insights.
Chemistry
; 18(14): 4337-44, 2012 Apr 02.
Article
in En
| MEDLINE
| ID: mdl-22383395
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.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Pyridones
/
Cobalt
/
Alkynes
/
Amides
/
Aminopyridines
/
Nitriles
Language:
En
Journal:
Chemistry
Journal subject:
QUIMICA
Year:
2012
Document type:
Article
Affiliation country: