Synthesis and some transformations of 7-substituted theophyllines

In the present study 7-(2-bromoallyl)- and 7-cinnamyltheophylline have been obtained by the interaction of alkenylhalides with theophylline in DMF in the presence of anhydrous potassium carbonate at 100 ºС in water bath. Fragmentation under electron ionization of the obtained 7-alkenyltheophyllines has been investigated by gas chromatography-mass spectrometry analysis, the main molecule fragmentation ways have been revealed. The mass spectra have been obtained on an UltraShimadzu GCMS-QP2010 and an Agilent 6890 N. The cinnamyl cation peak has the maximum intensity in the 7-cinnamylteophylline mass spectrum. The formation of tropylium cation ( m/z 91) is characteristic for the 7-cinnamylteophylline mass spectrum. In the case of 7-(2-bromoallyl)theophylline the elimination of bromine radical leads to formation of the peak with the maximum intensity. 7-(2,2,3-Tribromopropyl)theophylline and 7-(2,3-dibromo-3-phenylpropyl)theophylline have been synthesized by the addition of bromine to the double bonds of 7-(2-bromoallyl)- and 7-cinnamyltheophylline in CHCl3 at room temperature. The structures of reaction products have been confirmed by 1H NMR spectroscopy and gas chromatography-mass spectrometry. The structure of 7-(2,2,3-tribromopropyl)theophylline has been confirmed by X-ray analysis. The crystal contains two types of crystallographically independent molecules, the geometric parameters of which slightly differ. There is characteristic distribution of the molecular ion isotope peaks in the mass spectra of halogen-containing compounds: a doublet with an intensity ratio of approximately 1:1 for compounds with one bromine atom, a triplet of peaks in the case of two bromine atoms, and a quartet with an intensity ratio 1:3:3:1 for tribromoderivatives. In the case of 7-propargyltheophylline the reaction with bromine stops at the addition of one bromine molecule, which is proved by the formation of 7-(2,3-dibromoallyl)theophylline. It has been confirmed by 1H NMR and chromatography-mass spectrometry. Interaction of 7-(2,3-dibromopropyl)theophylline with o -phenylenediamine in acetonitrile at room temperature leads to the formation of quinoxaline ring. The 1H NMR spectrum contains characteristic signals of aromaticprotons at δ 6.85-7.05 ppm.