9-Isothiocyanatoacridines: Convenient Synthons for New Functionalized 9-Acridinyl Derivatives

Abstract

The specific physicochemical and spectral properties (dipole moments, NMR and fluorescence spectra) of 2- and 4-substituted 9-isothiocyanatoacridines were studied and compared with the series of m, p-substituted phenyl and benzoyl isothiocyanates. The high reactivity of heterocumulene bonds in the NCS group and that of 9 and 10 position in the acridine skeleton were utilized for the synthesis of new types of compounds, e.g. spiro dihydroacridine 9(10H),4′-thiazolines. Iminothiocarbonates or dithiocarbamates are the intermediates of these unusual addition-cyclization reactions. A new reagent, 1-azonium-4-azabicyclo[2.2.2]octane hydrogen-sulfide [DABCOH]⁽⁺⁾SH⁽⁻⁾, was developed for the preparation of hitherto inaccesible 9-acridinyl dithiocarbamates as well as 3-(9′-acridinyl)-5-substituted tetrahydro-1,3,5-thiadiazine-2-thiones. The reaction of iminothiocarbonates with bromoacetyl bromide represents a general method for the synthesis of 3-substituted 1,3-thiazolidine-2,4-diones from various type of isothiocyanates. The reaction of 9-hydrazinoacridine with 1-isothiocyanato-1-ethoxy-propane affords, instead of the expected 1,2,4-thiazoline derivative, the N-acridinium-9-yl-N’-propylidenehydrazine thiocyanate. The structures of the synthesized compounds were confirmed with IR, NMR, MAS spectra and X-ray analysis.