NEW SPIRO (THIO) BARBITURATES BASED ON CYCLOHEXANONE AND BICYCLO [3.1.1]HEPTAN-6-ONE BY NONCONCERTED [1+5] CYCLOADDITION REACTION AND THEIR CONFORMATIONAL STRUCTURES

Crossed-aldol condensation reaction of aromatic aldehydes with ketones such as; acetone and cyclohexanone leads to the efficient formation of cross conjugated alpha,beta-unsaturated ketones in excellent yield. The intermolecular and then intramolecular Michael addition reaction of alpha,beta-unsaturated ketones derived from acetone and cyclohexanone with (thio) barbituric acids lead to synthesis new type of 7,11-diaryl-2,4-diazaspiro[5.5]undecane-1,3,5,9-tetraone and 2,4-diaryl-1'H-spiro[bicyclo[3.3.1]nonane-3,5'-pyrimidine]2',4',6',9(3'H)-tetraone, respectively in good yield. Structure elucidation is carried out by H-1 NMR, C-13 NMR, FTIR, UV-Visible, mass spectroscopy and X-ray crystallography techniques. A possible mechanism of the formation is discussed. The structural conformation also demonstrated by coupling constants derived from dihedral angles between vicinal and geminal protons. The H-1 NMR spectra of NH protons of spiro compounds derived from barbituric acid show a broad singlet peak instead, these protons in the spiro compounds derived from thiobarbituric acid show two distinct peaks.