Pyrazolo benzothiazoles

Pyrazolo[4,3-g]benzothiazoles [CsNS-CsNa-Ce].—2 -7-Methyl-4,5-dihydropyra-zolo[4,3- ]benzothiazole (108) is obtained when compound (100) is treated with hydrazine or semicarbazide.  

andPharm. Bull. Japan), 1975, 23, 1696. 

Imidazo[2,l- ]benzothiazoles [CsNS-CsNj-Cg].—Further members of this class of compounds have been prepared by condensation of a 2-aminobenzothiazole with a substituted w-bromo-acetophenone. The imine (109) is converted into 2-methylimidazo[2,l-6]benzothiazole in dilute sulphuric acid in the presence of mercuric sulphate.  

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Oxidation of the hydrazone of 2-hydrazinopyrazole (226) with Pb(OAc)4 in CH2CI2 is a two-step reaction. The azine (227) was formed as an intermediate and this underwent ring closure to the 3H-pyrazolo[5,l-c][l,2,4]triazole (228) (79TL1567). A similar reaction applied to the benzal derivative of 2-hydrazinobenzothiazole (229) gave 3-phenyl-[l,2,4]triazolo[3,4-6]benzothiazole (230) together with a by-product (231) (72JCS(P1)1519). 

New pyrazolo[l,5-a]pyrimidine derivatives have been synthesized. These compounds are potent angiotensin-ll receptor antagonists <99CPB928>. Pyrazolot3,4-ri]dihydropyridazinone derivatives have been obtained by the reaction of 5-methyl-4-methoxycarbonyl-3-acetyl-1-phenylpyrazole with different hydrazines <99TL3891>. A direct synthesis of pyrazolo [3,4-b]pyridines 69 from pyrazole 67 and benzothiazole 68, through a Friendlander condensation, has been described <99SC655>. 

Bis-[2-( 1,3-benzothiazol-2-yl)-ethenyl]- 995 1,8-Dihydroxy-3,6-disulfo-2-(l, 3-thiazol-2-yl-azo)- 4 4-(3-Methy 1-1 H-pyrazolo)- -1,8-dicarbonsaure-anhydrid 610... 

In the recent years, Reis et al. [38] reported synthesis and anticancer activity of 2-(benzothiazol-2-yl)-8-substituted-2H-pyrazolo[4,3]quinolin-3(5H)-ones. The in-vitro anticancer activity of the synthesized compounds revealed, methyl and bromo substitution at C-6 position of quinoline showed considerable effect against three cancer cell lines. IC50 value of 2.3 mg/mL against breast cancer (MDA-MB-435), colon (HCT-8) and central nervous system (SF-295) cell lines (IC50 values of 4.1 and 4.5 mg/mL, respectively). 

Pyrazole and imidazole are alkylated in high yields on nitrogen with phase-transfer catalysis their A-alkyl derivatives, along with those of 1,2,4-triazole and benzotriazole, have been prepared by treatment of the TV-tributyltin compounds with alkyl halides.A range of A-alkyl-benzothiazolium salts has been synthesized from appropriate alkyl halides and benzothiazole, A-alkyl-phenothiazines (24) are similarly prepared,and some pyrazolo[l,5-a]pyri-midines (25) have been alkylated.In the alkylation of 2,5-dimethyl-3-... 

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