Studies on Spiroheterocycles, Part III: Synthesis of Diazaspiroundecanetetraone Derivatives Containing Biologically Active Heterocycles

Synthesis, photophysical studies, solvatochromic analysis and TDDFT calculations of diazaspiro compounds

Diazaspiro[5.5]undecane-1,3,5,9-tetraones and 3-thioxo-diazaspiro[5.5]undecane-1,5,9-trione have been synthesized via double Michael addition of 1,5-diphenyl-1,4-pentadien-3-one with active methylene heterocycles N,N-dimethyl barbituric acid, barbituric acid and thiobarbituric acid in water:ethanol (1:1) using TBAB as catalyst. The solvent effect on photophysical behavior of these compounds showed that stokes shift increases with increase in polarity of solvents. The solvent effect on the spectral properties has been investigated by using the Lippert-Mataga and Reichardt methods. The solvatochromism is analyzed by linear solvation energy relationship using the new four-parameter Catalán polarity scales. The relative fluorescence quantum yield of these diazaspiro compounds varies in solvents of different polarity. The HOMO and LUMO energies have been calculated by TDDFT (B3LYP/6-311G (d, p)) approach. TDDFT calculations were also used to compare the experimental and theoretical absorption spectra.

Synthesis, molecular structure and spectroscopic investigations of novel fluorinated spiro heterocycles

This paper describes an efficient and regioselective method for the synthesis of novel fluorinated spiro-heterocycles in excellent yield by cascade [5+1] double Michael addition reactions. The compounds 7,11-bis(4-fluorophenyl)-2,4-dimethyl- 2,4-diazaspiro[5.5] undecane-1,3,5,9-tetraone (3a) and 2,4-dimethyl-7,11-bis (4-(trifluoromethyl)phenyl)-2,4-diazaspiro[5.5]undecane-1,3,5,9-tetraone (3b) were characterized by single-crystal X-ray diffraction, FT-IR and NMR techniques. The optimized geometrical parameters, infrared vibrational frequencies and NMR chemical shifts of the studied compounds have also been calculated using the density functional theory (DFT) method, using Becke-3-Lee-Yang-Parr functional and the 6-311G(d,p) basis set. There is good agreement between the experimentally determined structural parameters, vibrational frequencies and NMR chemical shifts of the studied compounds and those predicted theoretically. The calculated natural atomic charges using NBO method showed higher polarity of 3a compared to 3b.The calculated electronic spectra are also discussed based on the TD-DFT calculations.