Thiazolo(oxazolo)thieno[b]pyrimidines. Preparation from 2-allylthio(oxy)thieno[2,3-d]pyrimidines and hydrolysis

Abstract

ChemInform Abstract The allyloxy(allylthio)thienopyrimidones (III), prepared by allylation of the phenolates(thiolates) (I), react with bromine or iodine to give the tricyclic compounds (IV) mentioned in the title.

Stereoselective synthesis of (E)-halomethylidene[1,3]thiazolo[3,2-a]thieno[3,2-e]pyrimidinium and analogous [1,3]oxazolo[3,2-a]thieno[3,2-e]pyrimidinium halides starting from 3-N-substituted 2-propargylthio(oxy)thieno[2,3-d]pyrimidin-4-ones

“…In the IR spectra of salts 5 and 6 , a bathochromic shift is observed for C = O and C = N + bands in comparison to the spectra of the substrates, which confirms the presence of a positively charged nitrogen in the molecule [ 27 ]. The ionic nature of products was confirmed by titration of the halide ion using equimolar quantities of AgBF 4 .…”

“…The starting thieno[2,3-d ]pyrimidine 1a -e , 2 [ 27 ] (20 mmol) was dissolved in 200 mL of ethanol (96%) containing sodium hydroxide (20 mmol) by heating. Propargyl bromide (25 mmol) was added to the cooled solution and the reaction mixture was heated for 1 h at 80 ° C. Then the mixture was allowed to cool to room temperature and the resultant solid product was fi ltered off , and washed with ethanol (20 mL) and warm water (50 mL).…”

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.…”

The Use of Electrophilic Cyclization for the Preparation of Condensed Heterocycles

“…For these purposes, unsaturated derivatives of aza-heterocycles are very suitable starting materials. As early as 1989, Khripak and co-workers 17 reported the preparation of tricyclic 1,3-thiazolo [3,2а]thieno [3,2-е]pyrimidinium salts 2 by the halocyclization of allyl thioethers of 3-phenylthieno [2,3-d]pyrimidines 1. Regardless of the substrate, higher yields of the target salts were achieved by using a solution of the halogen (2-3 equiv) in acetic acid at room temperature (Scheme 1).…”