Naphtho thiazolium salts

The use of thiazolium salts enables the benzoin condensation to proceed at room temperature. It can also be performed in dipolar aptotic solvents or under phase transfer conditions. Thiazolium salts such as vitamin Bi, thiazolium salts attached to y-cyclodextrin, macrobicyclic thiazolium salts, thiazolium carboxylate, ° naphtho[2,l-d]thiazolium and benzothiazolium salts catalyze the benzoin condensation and quaternary salts of 1-methylbenzimidazole and 4-(4-chlorophenyl)-4//-1,2,4-triazole are reported to have similar catalytic activity. Alkylation of 2-hydroxyethyl-4-methyl-l,3-thiazole with benzyl chloride, methyl iodide, ethyl bromide and 2-ethoxyethyl bromide yields useful salts for catalyzing 1,4-addition of aldehydes to activated double bonds. Insoluble polymer-supported thiazolium salts are catalysts for the benzoin condensation and for Michael addition of aldehydes. Electron rich al-kenes such as bis(l,3-dialkylimidazolidin-2-ylidenes) bearing primary alkyl substituents at the nitrogen atoms or bis(thiazolin-2-ylidene) bearing benzyl groups at the nitrogen atoms are examples of a new class of catalyst for the conversion of ArCHO into ArCHOHCOAr. 

N-Methylbenzothiazolone hydrazone hydrochloride (MBTH) is suitable for characterizing steroids such as 17-hy oxy-3,20-dioxopregn-4-en-21-al as osazones." N-Methylbenzothiazolium and naphtho[2,l-d]thiazolium salts (121) and (122) and certain dimers, e.g. (123), promote catalytically the acyloin condensation of benzaldehyde to benzoin." ... 

The quaternary pyrrolo[2,l-i>]quinazolinium salt 404 yielded the bis compound 405 with triethyl orthoformate in nitrobenzene in the presence of triethylamine at 190°C. The active methylene group of 404 readily react with the 2-[(2-acetanilido)vinyl] derivatives of 3-alkylbenzoxazo-lium, benzthiazolium, naphtho[2,l-acetic anhydride at 100 ° C in the presence of triethylamine to give the cyanines 406. Reaction of 404 with 3-ethyl-5-(acetanilidometh-ylene)rhodanine in refluxing pyridine in the presence of triethylamine af-... 

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