Desulfurization of pyrido[3′,2′:4,5]thieno-[2,3-f]pyrrolo[1,2-a][1,4]diazepines

Abstract

Pyrrolo[1,2-a] [1,4]diazepine derivatives are of interest from the viewpoint of searching for and developing novel substances with a variety of types of biological activity. For many years this fact has stimulated an active search for methods of synthesizing and modifying compounds of this class [1].It is known [2-4] that the thiophene ring in a thienopyridine fragment can readily undergo desulfurization with opening of the thiophene ring. In this work we report results of a study of the condensed pyrrolodiazepines transformation which contain a thieno[2,3-b]pyridine fragment.Amongst these derivatives we have examined the tetracyclic system of pyridothienopyrrolodiazepines 1a,b prepared by recyclization of N-(5-methylfuran-2-yl)methyl-substituted derivatives of 3-aminothieno[2,3-b]-pyridine amides using a known method [5] and we have looked at their reactions in the presence of Raney nickel.It was found that refluxing the diazepines 1a,b in ethanol in the presence of activated Raney nickel gave the desulfurization products, pyrrolodiazepines 2a,b which contain a pyridine ring conjugated to the diazepine fragment and whose structures were proved using NMR and mass spectrometric methods N S Me R Me NH 2 O N H O Me HCl / AcOH N S Me R Me NH N O Me N Me R Me NH N O Me EtOH 1a,b 60 o C 2a,bRaney Ni, 1,2a R = H, b R = Br 1 H and 13 C NMR spectra were recorded on a Bruker AM-300 instrument (300 and 75 MHz respectively) using DMSO-d 6 with TMS as internal standard. Mass spectra were taken on a Kratos MS-30 spectrometer with direct introduction of the sample into the ion source (EI, 70 eV).Compounds 1a,b were prepared by the method reported in [4]. Melting points and spectroscopic data agreed with those in the literature.