A CONVENIENT SYNTHESIS OF 2,3-DISUBSTITUTED DERIVATIVES OF 4H-PYRIMIDO[2,1-b]-BENZOTHIAZOLE-4-ONE

Simple and Efficient Synthesis of Novel Fused Bicyclic Heterocycles Pyrimido-Thiazine and Their Derivatives

“…The reaction of thiourea with α,β-unsaturated system (Michael acceptor) results in 1,3 thiazine [13,14]. It has been well focused that the presence of pyrimido-thiazine with various chemically reactive moieties is an important structural feature and also substituted imino group present in thiazine ring, and the resulting molecule would exhibit promising biological activities in continuation of our work [15][16][17][18][19][20][21]. In the present study, we synthesize pyrimido-thiazine containing more reactive functional groups using thiourea and bis methylthio methylene malanonitrile which is used for further cyclisation and derivatization.…”

Novel Synthesis of 3‐Amino‐4‐oxo‐(2H)‐pyrazolo[3′,4′:4,5]pyrimido‐[2,1‐b]benzothiazole and its 2‐ and 3‐Substituted Derivatives

“…Garin Javier et al [1][2] reported synthesis of 1-substituted derivatives of pyrazolo [3',4':4,5]pyrimido [2,1-b]benzothiazole from respective diphenyl pyrazolo pyrimidine thione and N-chlorosuccinimide in sulphuric acid. In continuation of our earlier work [4] on the synthesis of fused heterocycles containing bridgehead nitrogen atom, we report in this paper a convenient route for the synthesis of 3-amino-4-oxo-(2H)/aryl/heteryl pyrazolo [3',4 2-Amino benzothiazole in dimethyl formamide in the presence of anhydrous potassium carbonate was refluxed with ethyl-2-cyano-3,3-bismethylthio acrylate to get the required starting compound (1) which contains reactive thiomethyl group at the 2-position and a cyano group at the 3-position [4]. Compound (1) on heating independently with hydrazine hydrate, phenyl hydrazine, 2-hydrazino benzothiazole [5], 4-nitro phenyl hydrazine, 2,4-dinitro phenyl hydrazine and 6-nitro-2-hydrazino benzothiazole [5] in the presence of dimethyl formamide and a catalytic amount of potassium carbonate afforded 3-amino-4-oxo-(2H)/aryl/heteryl pyrazolo [3',4':4,5]pyrimido [2,1-b]benzothiazoles(3a-f) respectively in 42-60% yield(Scheme I).…”

Synthesis and antimicrobial activity of 2H-pyrimido[2,1-b]benzothiazol-2-ones

“…In view of the diverse rang of biological activities of pyrimidobenzothiazoles and our continuing interest in the design and synthesis of nitrogen and sulphur-containing bioactive heterocycles [17][18][19][20], it was considered interesting to synthesize hitherto unknown pyrimido [2,1-b]benzothiazoles in order to evaluate their antimicrobial activities. The synthesis of pyrimido [2,1-b]benzothiazoles has already been reported in the literature by annulation protocols involving two steps (via amidation of 2-aminobenzothiazoles) [14] or by multicomponent reactions [21][22][23][24][25][26], but in the present work we have synthesized pyrimido [2,1-b]benzothiazoles by a simple and convenient regioselective one-pot synthesis by the reaction of 2-aminobenzothiazole with alkynoic acid. All the synthesized pyrimido[2,1-b]benzothiazole-2-ones are new compounds and their structures have been characterized by IR, 1 H NMR, 13 C NMR, and mass spectral data.…”