Highly efficient synthesis and NMR features of novel fused pyrimidothiazinium trihalogenides

Abstract

Condensed pyrimidines are a popular class of heterocyclic compounds because they have a wide range of biological activity. This article aims to evaluate the simple, catalyst‐free procedure of synthesis of novel fused pyrimidothiazines. An efficient access to a series of pyrazolo[4′,3′:5,6]pyrimido[2,1‐b][1,3]thiazinium, pyrazolo[3′,4′:5,6]pyrimido[2,1‐b][1,3]‐thiazinium, and benzo[b]thieno[4′,3′:5,6]pyrimido[2,1‐b][1,3]thiazinium trihalogenides was developed via electrophilic heterocyclization of corresponding pyrimidine cinnamyl thioethers under the action of halogens. The XDR and complex NMR investigations were used for solving of final products structure; the anisochronism was observed in the NMR spectra of synthesized compounds for the pairs of ortho‐ and meta‐protons, as well as the N‐phenyl substituents associated with them.

Cyclizations of Alkenyl(Alkynyl)‐Functionalized Quinazolinones and their Heteroanalogues: A Powerful Strategy for the Construction of Polyheterocyclic Structures

“…[84][85][86][87][88][89][90][91] 2-Alkenyl substituted thioquinazolinones and thienopyrimidinones bearing a substituent at the pyrimidine N3 atom were found to react likewise with halogens. [92][93][94] Halomethyl-substituted fused thiazolopyrimidinones 49 proved to be appropriate substrates for structural modifications (Scheme 14). For instance, on treatment with NaOAc they are prone to the elimination of hydrogen halide and the formation of 1-methylene derivatives 51.…”

“…2‐Alkenyl substituted thioquinazolinones and thienopyrimidinones bearing a substituent at the pyrimidine N3 atom were found to react likewise with halogens [92–94] …”