A reinvestigation of the acid-promoted heterocyclization of 2-(2-oxo-2-arylethyl)malononitriles in the presence of amines.
The reinvestigation of the acid-promoted cyclization of 2-(2-oxo-2-arylethyl)malononitriles, in the presence of benzylamine or aniline, in ethanol or acetonitrile, has confirmed that this is a long-time reaction process for a low-yielding synthesis of 2-amino-5-arylfuran-3-carbonitriles (2), or 2-amino-5-aryl-1-phenyl-1H-pyrrole-3-carbonitriles (4), depending on the base used. However, the microwave-assisted synthesis of 2-amino-5-(4'-methoxyphenyl)furan-3(4)-(di)carbonitriles (2c and 3c) proceeds in shorter reaction times and higher yields than does the classical thermal heating protocol. In these reactions we have observed for the first time, and characterized by their spectroscopic data and X-ray analysis, the unexpected formation of 2-amino-5-aryl-3 (4)-(di)carbonitriles (3), whose formation has been rationalized by density functional theory (DFT) analysis of the proposed reaction mechanism.
Martins
Carla
C
iMedUL, Research Institute for Medicines and Pharmaceutical Sciences, Faculty of Pharmacy, University of Lisbon, Lisbon, Portugal.
Eleutério
Ana
A
Carreiras
M Carmo
MC
Samadi
Abdelouahid
A
Soriano
Elena
E
Léon
Rafael
R
Marco-Contelles
José
J
D000588:Amines / Q000737:chemistry*; D018360:Crystallography, X-Ray; D003500:Cyclization; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D008968:Molecular Conformation; D009570:Nitriles / Q000737:chemistry*; D013237:Stereoisomerism; D013816:Thermodynamics
D000588:Amines; D009570:Nitriles; C000945:dicyanmethane