Table 1 NHC systems employed in the study
Skeletal structure X R R’ Label
Imidazol-2-ylidene Thiazol-2-ylidene Oxazol-2-ylidene
N
H
H
IH
N -CH3 -CH3 IMe
N -NH2 -NH2 INH2
N -CN -CN ICN
N Mes Mes IMes
S H Nil ISH
S -CH3 Nil ISMe
O H Nil IOH
O -CH3 Nil IOMe
Benzimidazol-2-ylidene
N
H
H
BH
N -CH3 -CH3 BMe
Tetrahydropyrimidin-2-ylidene N H H TH
N -CH3 -CH3 TMe
Permidin-2-ylidene N H H PH
N -CH3 -CH3 PMe