The synthesis of some 4H‐pyrimido[2,1‐b]benzothiazol‐4‐ones

Abstract

A series of 8‐substituted and 7,8‐disubstituted‐4‐oxo‐3‐(4H‐pyrimido[2,1‐b]benzothiazole)carboxylic acids and esters including a 9‐aza analog were synthesized from substituted 2‐aminobenzothiazoles and diethyl ethoxymethylenemalonate. The 9‐aza analog, ethyl 8‐methoxy‐4‐oxo‐3‐(4H‐pyrido[3′,2′:4,5]thiazolo[3,2‐a]pyrimidine)carboxylate (56), represents the first preparation of this new heterocyclic ring. These compounds were examined for antiparasitic activity, however, no significant activity was detected.

Synthesis of pyrimido[2,1-b][1,3]benzothiazoles and [1,3]benzothiazolo[3,2-a]quinazolines via one-pot three-component reactions from 2-aminobenzothiazole, arylglyoxals and 1,3-dicarbonyl compounds

“…Most of the methods depict syntheses of pyrimido[2,1-b] [1,3]benzothiazole and [1,3]benzothiazolo [3,2-a]quinazoline derivatives from intermolecular cyclization of 2-aminobenzothiazoles with malonic ester derivatives, 2,12 Meldrum's acid, 13 and β-ketoesters. 14 The reaction of 2-aminobenzothiazoles with various Michael acceptors, such as acetylenic compounds, 15,16 alkyl malonates, 8,17 and enaminones. 18 Moreover, organic and medicinal chemists have developed a series of multicomponent reactions (MCRs) for the synthesis of heterocyclic compounds and complex biologically-active compounds, [19][20] such as multi-component reaction of 2-aminobenzimidazole, benzaldehyde derivatives, and active methylene compounds, 6,[21][22] and various other methods.…”

Novel synthesis and biological activity of 2‐substituted derivatives of 3‐cyano‐4‐imino‐2‐methylthio‐8‐methoxy‐4H‐pyrimido[2,1‐b][1,3]benzothiazole and 3‐amino‐4‐imino‐8‐methoxy‐2H‐pyrazolo[3′,4′:4,5]pyrimido[2,1‐b][1,3]benzothiazole

“…Fused pyrimidobenzothiazoles [1,2] are well known for their varied biological activities like antiallergic [3,4], antitumor [5], anti-inflammatory [6], antiparkinsonism [7], and phosphodiesterase inhibition [8]. In our recent publications [9][10][11][12], we have outlined convenient synthesis of new fused heterocyclic systems like oxopyrimidobenzothiazoles [9,10], pyrazolopyrimidobenzothiazoles [11], and benzothiazolotriazepines [12] and studied on their biological activities [12].…”

A New and Efficient Method for the Synthesis of Pyrimido[2,1-<i>b</i>]Benzothiazole Derivatives

“…Additionally, these compounds are incorporated with pyrazole structure known to possess tranquilizing, psychoanalytic and muscle relaxant activities [5][6][7]. Pyrimidobenzothiazole derivatives have also been known for their antimicrobial properties [8][9][10], anti-allergy [11], antitumor and anti-viral activities [12]. Meanwhile, oxopyrimido benzothiazoles have been assessed for bronchodilators, and bronchial asthma treatment [13].…”

“…Therefore, a variety of effective strategies have been developed for the synthesis of these compounds. Most of the methods depict synthesis of pyrimido[2,1-b]benzothiazole derivatives from 2-amino benzothiazoles and β-haloesters [8][9][10], orthoesters [14][15][16][17], allenic [18] and acetylenic groups [19][20][21][22][23][24][25]. Even though in some methods β-ketosters [26,27], α-haloacids [28] and malonates [29] have been used.…”