Thiazol-3-ones, 2-alkyl-, preparation

Very simple and straightforward alkylation of NH-heterocycles (NaH, Cl(CH2) SMe, = 2 or 3, 68-86%) permits one-pot preparation of pyrrole and carbazole sulfide models for the reaction with triflic anhydride <2003S1191>. Cyclization of the (l/7-pyrrol-l-yl)alkyl sulfides 1470 obtained leads to 2,3-dihydropyrrolo[2,l- ][l,3]thiazole 1472 and 3,4-dihydro-2/7-pyrrolo[2,T ][l,3]thiazine 1473 via intermediate l-methyl-2,3-dihydropyrrolo[2,l-/ ][l,3]thiazol-1-ium or l-methyl-3,4-dihydro-27/-pyrrolo[2,T ][l,3]thiazin-Tium salts 1471 (n = Z or 3), respectively, that were isolated in high yields in most cases (Scheme 281) <2003S1191>. 

Russian authors investigated this important reaction type to prepare a wide range of aryl-, alkyl-, and acyl-substituted imidazo[2,l-ft]thiazoles (70KGS508, 70KGS512 71KGS389). Several 2-mercaptoimidazoles react with a-halo ketones in one step directly to the bicyclic products 35 under reflux in butanol or ethanol followed by basification. Yields vary between 52 and 99%, but the two-step cyclization route requires isolation of the intermediates 34 and subsequent heating in phosphorus oxychloride. 

Diary] and triaryl or naphthyl carbamates exhibit low herbicidal activity. The substitution of the aryl radical for a heterocyclic radical gives heterocyclic alkyl and dialkyl ureas, of which many examples have been prepared in recent years. The herbicidal activity of urea derivatives containing a heterocyclic radical, such as benzthiazole, thiazole, thiadiazole, oxadiazole and pyridine, is favourable if one or two methyl groups are substituted at the N -nitrogen. The carrier of total or selective action in these derivatives is presumably the heterocyclic part of the molecule. More recently several new groups of compounds have become known, mainly in the patent literature, for which the structure-activity on relationships are still to be elucidated. 

Ring opening of l,3-thiazole-5(4ff)-one 91 with a-aminoalkyl esters 92 in the presence of 1-hydroxybenzotriazole and iV-ethyl diisopropylamine gives the endothiotripeptide 93 (Eq. 32) [54]. The starting compound 91 is prepared by the ( )-camphor-10-sulfonic acid-catalyzed cydization of endodipeptide.The reaction with 92, where a bulky alkyl group is introduced to the carbon atom... 

Interconversion of thiono- and dithio-esters has been considered earlier (p. 179). The reaction of these compounds with amines has remained one of the most important and widely applied methods for the preparation of thioamides and related substances. This is especially true for carboxymethyl dithio-benzoates, - but other alkyl dithiocarboxylates > > - or RC(S)SSR work as well in many cases. For example, MeCSaMe reacted with amino-acids, free peptides, and peptides which were fixed to a polystyrene matrix, and the terminal A-thioacetyl amino-acid was split off by CF3CO2H to give 2-substituted thiazol-5-ones, which served to identify the -terminal amino-... 

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