Synthesis of 7-carboxyalkylthio-5,6,7,8-tetrahydro-1H-pyrazolo[3,4-e]diazepin-4-ones

Abstract

The article describes the method of synthesis of a new type of pyrazolo[3,4-e][1,4]diazepin-4-ones substituted in position 7 by fragments of thioalkane carboxylic acids. The literature reference considers the synthetic and biological studies of heterocyclic compounds with exo-functionalized fragments of thioalkan carboxylic acids and it substantiates the expediency of our investigation. The results of the research are development of an effective one pot method for the target compounds, which is based on the intramolecular cyclization of 5-amino-N-(2,2-dialkyloxyethyl)pyrazole-4-carboxamides in the solution of formic acid with thioalkan carboxylic acids. The synthesis of the starting 5-aminopyrazolo- 4-carboxamides has been performed by condensation of 2-cyano-N-(2,2-dimethoxy)-3-dimetylaminoacryl(croton) amides with alkyl hydrazines or hydrolytic cleavage of 5-(2,2-dietoxyethyl)-1,5-dihydropyrazolo-4Н-[3,4-d]pirimidin- 4-ones. The scheme of this reaction proposed involves the intramolecular cyclocondensation with the initial formation of the corresponding 7-hydroxy-5,6,7,8-tetrahydropyrazolo[3,4-e][1,4]diazepin-4(1H)-ones, and further replacement of the hydroxyl group for the carboxyalkylthiol residue in the acidic medium. The structure of the compounds obtained has been proven using the methods of IR-, NMR 1H 13C-spectroscopy, mass-spectra and elemental analysis. The substantial evidence of the diazepine cycle formation is the presence of multiplets of protons H6 in the range of 3.16- 3.50 ppm and multiplets of protons H7 in the range of 4.89-5.17 ppm in the 1Н NMR spectra.