Thiocarbamates formation

Thioamide formation benzodiazepinone, 505 heteiodiazepinone, 621 phosphorus pentasulf ide, 323, 600 Thioazole formation, nitrile addition, 301 Thiocarbamate formation, 588 phenol, 95 rearrangement, 517 Thioenol ether formation, 185, 517 addition-elimination, 554 Thioester formation, mixed anhydride, 184 Thioether formation, 241, 300, 413, 416 alkylation, 586, 588 aromatic displacement, 416 Thiohydantoin formation, 293 Thiol interchange, benzothiazole formation, 422... 

The position of a trimethylsilyl substituent in phenols 33 determines great yield differences in both thiocarbamate formation and rearrangement [57, 58]. The required TMS-substituted phenols, which were prepared from the respective bromophenols, were tested under standard conditions (Scheme 19). The yield of the rearrangement decreased as the substituent moved from para to ortho. 

The toxic nature of mercury and its compounds has caused concern over environmental pollution, and governmental agencies have imposed severe restrictions on release of mercury compounds to waterways and the air (see Mercury). Methods of precipitation and agglomeration of mercurial wastes from process water have been developed. These methods generally depend on the formation of relatively insoluble compounds such as mercury sulfides, oxides, and thiocarbamates. MetaUic mercury is invariably formed as a by-product. The use of coprecipitants, which adsorb mercury on their surfaces facihtating removal, is frequent. 

Salt formation with Brmnsted and Lewis acids and exhaustive alkylation to form quaternary ammonium cations are part of the rich derivati2ation chemistry of these amines. Carbamates and thiocarbamates are formed with CO2 and CS2, respectively the former precipitate from neat amine as carbamate salts but are highly water soluble. 

Reaction of equimolar amounts of the thiocarbamate (91) with (chlorocarbonyl)sulphenyl chloride gave l,2,4-dithiazoline-5-one (92) and the 1,2,4-thiadiazole (93) the relative amounts of (92) and (93) being very dependent on the solvent used in the reaction. The mechanism of formation of both (92) and (93) was discussed <96JOC6639>. 

Formation of enantio- and diastereoenriched l-aza-4-oxa-7-thiabicyclo[3.3.0]octan-8-ones 453a and 453b was accomplished by ring closure of acyl-substituted. Y-bcnzyl thiocarbamates 452 in presence of Amberlyst 15 and 1,3-propanedithiol via a rearrangement of the oxazolidine ring (Equation 213) <2000JPR828>. 

The reaction of 2-aminobenzyl alcohol 376 with 2-chloro-4,5-dihydroimidazole afforded [2-(4,5-dihydro-177-imidazol-2-ylideneamino)phenyl]methanol hydrochloride 377, which upon treatment with carbon disulfide gave l-(477-3,l-benzoxazin-2-yl)imidazolidine-2-thione 378 (Scheme 71). The assumed reaction mechanism involved the initial formation of the dithiocarbamate 379, which underwent intramolecular nucleophilic addition to furnish the unstable thiazetidine 380. By nucleophilic attack of the hydroxy group on the carbon atom of the thiazetidine ring, thiocarbamate derivative 381 was formed, which gave the final 3,1-benzoxazine 378 by an intramolecular cyclocondensation with the evolution of H2S <2006H(68)687>. 

The sense and degree of asymmetric induction of the Pd(0)-catalyzed rearrangement of the cyclic and acyclic O-allylic thiocarbamates in the presence of BPA are the same as, or similar to, those in the Pd-catalyzed substitutions of the corresponding cyclic and acyclic racemic allylic carbonates and acetates with sulfinates and thiols. It is therefore proposed that Pd(0)/BPA reacts with the racemic O-allylic thiocarbamate with formation of a jt-allyl-Pd(II) complex, which contains as counter ion the corresponding thiocarbamate ion (Scheme 2.1.4.19) [23, 24]. Substitution of the jt-allyl-Pd(II) complex by the thiocarbamate ion gives the S-allylic thiocarbamate and the Pd catalyst. 

The chemical complexing-solvent extraction technique employed in this work involved the formation of a neutral complex in the aqueous phase between trialkyl lead chloride and a dithiocarbamate reagent such as sodium diethyl di-thiocarbamate. The complex was subsequently removed either as a precipitate or by extraction into an organic solvent. The extent of lead removal was traced by analysis of the aqueous phase for residual trialkyl lead using a Pye-Unicam 8000 spectrophotometer. 

Similar absolute asymmetric synthesis was demonstrated in the solid-state photoreaction of A-(P,y-unsaturated carbonyl)thiocarbamate 41. [27] Achiral 0-methyl AT-(2.2-dmeth ibut-3-enoyl)-iV-phenylthiocarbarnate 41 crystallized in chiral space group P2i, and irradiation of these crystals gave optically active thiolactone in 10-31% ee. A plausible mechanism for the formation of 42 is rationalized on the basis that photolysis of 41 undergoes [2 + 2] cyclization to thietane and is subsequently followed by rearrangement to thiolactone 42. 

It has been reported <1998CC2315> that a similar [2+2] intramolecular cyclization of (2-cyclohex-l-enyl-2-methyl-propionyl)phenyl-thiocarbamic acid O-methyl ester leads to the formation of tricyclic thietane in 85% yield (Table 2). 

All authors seem to claim that for MMA the photochemical chain extension of thiocarbamate-terminated PMMA appears to be a more complicated process. Turner and Blevins [236] have shown that, during the process, the formation of CS2 is not negligible, unlike the polymerization of styrene, and they explained its production by the following scheme ... 

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