6- imidazo thiazoles bromination

Treatment of 6-(2 -furanyl)imidazo[2,l-b]thiazole (65) with bromine in chloroform gave rise to products of bromination of both furan and imidazole moieties (80MI1). In the unsubstituted imidazothiazole, bromination in dimethylformamide at 80°C, or in dichloromethane at 0°C, occurred in the 5-position. Even when there are such reactive groups as 2 -furanyl or... 

Under basic conditions, A -acridinylmethyl-substituted thiourea 449 placed in the presence of bromoacetonitrile gave rise to the unexpected formation of the spiro[dihydro-acridine-9(10//),2 -(2, 7 -dihydro-3 //-imidazo[l,2-c]thiazol-5 -ylidene-/>-nitrophenyl)amine] 450 in 67% yield. The reaction involved displacement of the bromine atom of... 

When l-methyl-2-(2 -furyl)imidazole (7) was brominated under conditions that either protonate or complex the azole nitrogen, substitution was directed mainly into the furan nucleus. Bromine only enters the imidazole ring in neutral organic solvents (89CHE1168) (Scheme 2) In 6-(2 furan yl)-imidazo[2,l-b]thiazole and some of its methyl derivatives, both furan-5-and imidazole-4-positions were brominated (80MI1). 

Treatment of the thiazolium sail (249) with base gives the imidazo[2,1 -b]thiazole (250) (64CPB813). Bromination of the hydrochloride of (251) in the presence of KOAc proceeds with simultaneous cyclization to give 3-oxo-6-bromomethyl-2,3,5,6-tetrahydroimidazo[2,l-6]thiazoles (252) (73CHE395). Imidazole-4-carbaldehyde reacts with vinyltriphenylphos-phonium bromide in the presence of NaH to give 5H-pyrrolo[l,2-c]imidazole, presumably via an allenic intermediate (equation 47). Imidazole-2-carbaldehyde reacts analogously... 

Among other condensed thiazole ring systems, imidazo[2,l-6]thiazoles (tetramisole is a member of this class), thiazolo-pyrimidines, and thiazolo-pyridines continue to attract the most interest. Attention is concentrated on synthesis and biological activity. Unexpectedly, dihydrothiazolo[3,2-a]pyridinium bromide is readily brominated when the pyridine ring has a 3-nitro-substituent but not when it has a 3-amino-substituent. 

Tmidazo[2,l-Z)]thiazole has been shown by n.m.r, spectroscopy to protonate on the N-atom of the imidazole ring, whilst the mass spectra of some 2-alkyl-substituted imidazo[2,l-6]thiazoles have been correlated with their structures. Compound (69) is brominated in the vacant imidazole ring position by bromine in acetic acid or with sodium hypobromite, but bromination with bromine in chloroform occurs preferentially in the vacant a-position of the furan ring, and in this case a mixture of mono- and di-bromo-compounds is obtained. Compound (69) undergoes the Mannich reaction preferentially in the vacant imidazole ring position the products undergo further substitution e.g. nitration) in the a-position of the furan ring. ... 

Amination of the imidazo[2,l-/>]thiazoles (70 R = Me or Ph) with 0-(mesitylenesulphonyl)hydroxylamine yields salts that react with bromine water to give dimeric 7,7 -azoimidazo[2,l-A]thiazolium dibromides. The reaction of 2-substituted 5,6-diphenyl-2,3-dihydroimidazo[2,l-6]thiazol-3-ones... 

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