Synthesis of Substituted 2-Benzoylaminothiobenzamides and Their Ring Closure to Substituted 2-Phenylquinazoline-4-thiones

Jiří Hanusek,Ludmila Hejtmánková,Miloš Sedlák,Lenka Kubicová

doi:10.3390/60400323

Abstract

Acylation of 2-aminothiobenzamide or 2-methylaminothiobenzamide with substituted benzoyl chlorides has been used to synthesise the corresponding 2-benzoyl-aminothiobenzamides whose subsequent sodium methoxide-catalysed ring closure gives the corresponding quinazoline-4-thiones. These compounds were characterised by means of their 1H- and 13C-NMR spectra. The preferred tautomeric form of selected compounds has been discussed on the basis of their 13C-NMR, IR and Raman spectra. It has been found that in the given medium 1-methyl-quinazoline-4-thiones undergo a replacement of the sulphur substituent by oxygen giving 1-methyl-quinazoline-4-ones. In strong acid media, 2-benzoylaminothiobenzamide is cyclised through its sulphur atom to give 2-phenylbenzo[d-1,3]thiazin-4-one.

Highlights

Quinazoline-4-thiones can be synthesised by several ways: e.g. it is possible to transform the corresponding oxygen derivative into its sulphur analogue by treating it with phosphorus pentasulphide [4] or Lawesson’s reagent [5]
In our work we have chosen the way of constructing the heterocyclic skeleton which consists in the acylation of 2-aminothiobenzamide or 2-methylaminothiobenzamide with substituted benzoyl chlorides and subsequent ring closure of the obtained 2benzoylaminothiobenzamides (1a-m) in basic medium to give the quinazoline-4-thiones (2a-m) (Scheme 1)
The 2-benzoylaminothiobenzamides and 1-methyl-2-phenyl-1H-quinazolin-4-thiones prepared by new methods have not been described yet

Summary

Introduction

Quinazoline-4-thiones can be synthesised by several ways: e.g. it is possible to transform the corresponding oxygen derivative into its sulphur analogue by treating it with phosphorus pentasulphide [4] or Lawesson’s reagent [5]. It is possible to make use of the reactivity of suitably substituted isothiocyanates [6]. In our work we have chosen the way of constructing the heterocyclic skeleton which consists in the acylation of 2-aminothiobenzamide or 2-methylaminothiobenzamide with substituted benzoyl chlorides and subsequent ring closure of the obtained 2benzoylaminothiobenzamides (1a-m) in basic medium to give the quinazoline-4-thiones (2a-m) (Scheme 1)

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Results

Conclusion