This paper presents the synthesis and characterizations of some semicarbazone and thiosemicarbazone derivatives of 3-phenylquinazoline-2,4(1H,3H)-dione. All compounds reported here had been characterised by 1H NMR and IR spectral studies... more
This paper presents the synthesis and characterizations of some semicarbazone and thiosemicarbazone derivatives of 3-phenylquinazoline-2,4(1H,3H)-dione. All compounds reported here had been characterised by 1H NMR and IR spectral studies and elemental analysis. semicarbazone and thiosemicarbazone derivatives of 3-phenylquinazoline-2,4(1H,3H)-dione were prepared by treating mixture of phenyl isocyanates and anthanilic acid in ethanol to get 3-phenylquinazoline-2,4(1H,3H)-dione which will then condense with substituted 4-chloro/bromo/iodo Acetophenones in ethanol to form the chalcones .this chalcones were treated with semicarbazide and thiosemicarbazide in ehanol to get semicarbazone and thiosemicarbazone derivatives of 3-phenylquinazoline-2,4(1H,3H)-dione to explore the biological activities and importance as ligands for various transition metal complexes.
Condensation of 4tertbutyl2,6diformylphenol with 1,2diaminobenzene in ethanol is accompanied by partial reduction of the azomethine double bonds to form symmetrical macro cyclic Schiff's base containing the alternating >C=N and... more
Condensation of 4tertbutyl2,6diformylphenol with 1,2diaminobenzene in ethanol is accompanied by partial reduction of the azomethine double bonds to form symmetrical macro cyclic Schiff's base containing the alternating >C=N and >CH—NH fragments. In solution, this compound exists as the only isomer in which two endocyclic hydrogen atoms are bound to the oxygen atoms of the phenol groups and two other endocyclic H atoms are attached to the nitrogen atoms of the CH2—NH fragments. All endocyclic protons are involved in hydrogen bonding and undergo rapid exchange with each other at room temperature. In the crystal, the planar macrocyclic molecules are arranged in closely packed stacks. The steric hindrances resulting from overlapping of the bulky tertbutyl groups are eliminated through rotation of the molecules with respect to each other in the adjacent layers. Study of the potential energy surface for the Schiff's base under consideration by the DFT method demonstrated that the structure corresponding to the global minimum is similar to that found in solution. However, the isolated molecule is nonplanar, its macrocycle adopting a ladder conformation. The local minimum on the potential energy surface whose energy is 2.6 kcal mol–1 higher than that of the global minimum corresponds to the zwitterionic structure in which all four endocyclic hydro gen atoms are attached to the nitrogen atoms and the macrocycle adopts a tub conformation. Flattening of the ring is considered as a consequence of stacking interactions between the molecules in the crystal.
