Thiocarbamates from isothiocyanates

Cyanoamido-thiocarbamates, from cyan-amide and isothiocyanates, 297 Cyanohydrin, benzene sulfonates, synthesis of, from sodium cyanide and haJo-benzaldehyde, 297... 

DiaminO 4,4-dimethyl-l,3,5-thiadiazine hydrobromide was isolated as by-product (418). Benzene sulfonates of cyanohydrin prepared from sodium cyanide and an halobenzoaldehyde, when treated with thiourea or its derivatives, afford 2,4-diamino-5-(p-halogenophenyl)-thiazole benzene sulfonates (447). Similarly, cyanoamido thiocarbamates obtained from cyanamide and isothiocyanates yield substituted 2,4-diaminothiazoles (598). 

Synthesis of ds-fused OZT starting from 2-amino-2-deoxy-D-glucose and D-mannose hydrochlorides in conditions similar to those applied for glycosylamines was recently published (Scheme 6).36 In contrast with data previously reported for tram-fused thiocarbamate,32 the isomeric isothiocyanates were not detected. 

An alternative method for the synthesis of different dextran conjugates with fluorescent dyes is the reaction of a water-soluble amino dextran with the succinimidyl ester of the corresponding dye [360]. The amide linkage is more stable than the corresponding thiocarbamate formed with isothiocyanates. This method is displayed schematically in Fig. 54 for the preparation of 5- (and 6-) carboxynaphthofluorescein-labelled dextran from amino dextran (Fig. 47, [361,362]). 

Many strained four-membered heterocycles, containing three heteroatoms, with at least one heavier group 14 element, are moisture, thermo- or light-sensitive compounds. For example, separation from the reaction mixture of 1,3,2-oxathiasiletane 63 furnished not the expected compound, but the hydrolyzed product, a thiocarbamate (Scheme 3) <2000CL244>. The adduct 64 is moisture stable and can be chromatographically purified. However, it is sensitive to gradual hydrolysis with the liberation of phenyl isothiocyanate <2002CL34>. 

A major route to 2-amino-6/f-l,3,4-thiadiazines is by the condensation of a-haloketones with thiosemicarbazides (Section 6.17.7.2.2(ii)). Replacement of the thiosemicarbazide by a thiocarbamic acid or by a thiocarbazide results in formation of 3,6-dihydro-2//-l,3,4-thiadiazin-2-ones. Likewise, replacement with an A -arylthiohydrazide yields a 4//-l,3,4-thiadiazin-5(6/f)-one (Section 6.17.7.2.2(ii)). 3,6-Dihydro-27/-thiadiazin-2-ones are also available by the condensation of alkyl-hydrazines with a-(methoxycarbonylsulfenyl)alkylaryl ketones (Section 6.17.7.2.2(vi)), while the ring closure of (arylhydrazonoalkylthio)acetic acids with dicyclohexylcarbodiimide provides an alternative route to 4 -l,3,4-thiadiazin-5(677)-ones (Section 6.17.7.1.2). 2-Phenylimino-3-aryl-2,3-dihydro-l,3,5-thiadiazin-6-ones result from treatment of a-hydrazono-j8-ketoesters with aryl-isothiocyanates (Section 6.17.7.2.2(iv)). 

Starting from 1,2-0-sulfinyl-a-D-glycopyranose or glycofuranose. Treatment of the Q -l,2-0-sulfinyl derivative with sodium thiocyanate led to a p-thiocyanate that, imder the reaction conditions was isomerized to a transient a-isothiocyanate via an oxocarbenium ion. The isothiocyanate underwent spontaneous annelation with a vicinal hydroxyl group to afford the corresponding glycopyrano and glycofurano cis-fused thiocarbamates (Scheme 13). 

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