Dithio-carbonates

Various S-nucleophiles are allylated. Allylic acetates or carbonates react with thiols or trimethylsilyl sulfide (353) to give the allylic sulfide 354[222], Allyl sulfides are prepared by Pd-catalyzed allylic rearrangement of the dithio-carbonate 355 with elimination of COS under mild conditions. The benzyl alkyl sulfide 357 can be prepared from the dithiocarbonate 356 at 65 C[223,224], The allyl aryl sufide 359 is prepared by the reaction of an allylic carbonate with the aromatic thiol 358 by use of dppb under neutral condi-tions[225]. The O-allyl phosphoro- or phosphonothionate 360 undergoes the thiono thiolo allylic rearrangement (from 0-allyl to S -allyl rearrangement) to afford 361 and 362 at 130 C[226],... 

Reactions. The chemistry of the xanthates is essentially that of the dithio acids. The free xanthic acids readily decompose in polar solvents, the rate being 10 times greater in methanol than in hexane. The acids decompose at room temperature to carbon disulfide and the corresponding alcohol the resulting alcohol autocatalyticaHy faciUtates the decomposition. 

Nitrogen nucleophiles used to diplace the 3 -acetoxy group include substituted pyridines, quinolines, pyrimidines, triazoles, pyrazoles, azide, and even aniline and methylaniline if the pH is controlled at 7.5. Sulfur nucleophiles include aLkylthiols, thiosulfate, thio and dithio acids, carbamates and carbonates, thioureas, thioamides, and most importandy, from a biological viewpoint, heterocycHc thiols. The yields of the displacement reactions vary widely. Two general approaches for improving 3 -acetoxy displacement have been reported. One approach involves initial, or in situ conversion of the acetoxy moiety to a more facile leaving group. The other approach utilizes Lewis or Brmnsted acid activation (87). 

From the reactions of sulfur and carbon disulfide with cyclic ketone-derived enamines (570-573) 3H-l,2-dithiole-3-thiones were obtained, whereas the addition of carbon disulfide to other enamines gave a-dithio-pyrones (574), through initial dimerization of the enamine. 

Dithio acids and dithiols are formed by reaction of carbon disulfide with various nucleophiles (Z or Z ), as follows. 

Considerably less is known about the chemistry of palladium and platinum 1,1-dithio complexes. Of late, there has been only one report that dealt with the synthesis of a large number of palladium dithiocar-bamates 392). Twenty-five yellow palladium dithiocarbamate complexes were obtained by reaction of PdCla with NaR2dtc in methanol solution. Several other reports have appeared in which a few dithiocarbamate complexes of palladium were synthesized. Thus, the novel [Pd (OH)2dtc 2], which is soluble in water, was isolated 393). The synthesis of optically active palladium(II) complexes of AT-alkyl-a-phen-ethyldithiocarbamates, similar to (XXIV), via the reaction between the optically active amine, CS2, and PdCl2, has been described. From ORD and CD spectra, it has been established that the vicinal contribution of a remote, asymmetric carbon center could give rise to optical activity of the d—d transitions of palladium 394). Carbon disulfide has been shown to insert into the Pt-F bond of [PtF(PPh3)3]HF2, and X-ray studies indicated the structure (XXIX). 

The isolation, separation, and chemistry of dithio- and perthioaryl-carboxylate complexes of Ni(II), Pd(II), and Pt(II) were reported in two complementary reports (381, 415). The perthiocarboxylate complexes have also been obtained by oxidative addition of sulfur to the dithiocar-boxylic acid complexes. The abstraction of the sulfur atom adjacent to carbon by PPha was again observed, and rationalized as follows. 

The alkylating agent (50 mmol) is added to a stirred solution of potassium O-alkyl dithio-carbonate (50 mmol) and Aliquat (1.68 g, 4 mmol) in H20 (50 ml). The mixture is stirred until the aqueous phase is completely colourless (Table 4.8) and petroleum ether (b.p. 40-60 °C, 150 ml) is then added. The organic layer is separated, dried (MgS04), filtered through silica, and evaporated under reduced pressure to yield the 0,5-dialkyl ester. 

Potassium 0-(2-propyl) dithiocarbonate Carbonic acid, dithio-, O-isopropyl ester, potassium salt (8) Carbonodithioic acid, O-(l-methylethyl) ester, potassium salt (9) (140-92-1)... 

Figure 6. Carbon monoxide difference spectrum of partially purified hepatic microsomal Cytochrome P-451 from DBA-treated male little skates. The cuvettes contained dithionite-reduced cytochrome (0.15 mg protein/mL) in lOmM phosphate buffer, pH 7.7, containing 20% glycerol, O.lmM EDTA and O.lmM dithio-...

A polypyrrole film electrochemically deposited on gold electrodes from an MeCN-liCl04/Co(OAc)2 solution shows electrocatalytic activity in dioxygen reduction [404]. The catalytic electroreduction of dithio dipropionic acid (PSSP) with the water-soluhle cohalt(II I)tetrakis(4-trimethyl-ammonium phenyl) porphyrin (CoTMAP) has heen studied. The Co catalyst adsorbed on the glassy carbon electrode plays a major role in the electroreductive cleavage of the S—S bond [405]. 

Similarly, the influence of pulp potential on the flotation of marmatite, arsenopyrite and pyrrhotite with 10 mol/L butyl xanthate as a collector in the presence of 120mg/L (1-carbonic sodium-2-acetaic sodium) propanic sodium dithio carbonic sodium (TX4) has been tested. The results are given in Fig. 5.26 and Table 5.2. It can be seen from Fig. 5.26 that at pH=4.5 marmatite has wide floatable potential range from 0.3 V extended to above 0.7 V, at pH = 6.5 the floatable potential range is about 0.3-0.4 V, and at pH =9.2 marmatite is not floatable. Table 5.2 demonstrates that in these conditions, arsenopyrite and... 

Figure 5.29 and Fig. 5.30, respectively, show the adsorption of (1-carbonic sodium-2-acetaic sodium) propanic sodium dithio carbonic sodium (TX4) on... 

It can also be seen from Fig. 5.33 that with the increase of (1-carbonic sodium-2-acetaic sodium) propanic sodium dithio carbonic sodium (TX4), the negative zeta potential of marmatite, pyrrhotite and arsenopyrite increase. The negative zeta potential reach the maximum and remained stable at the concentration of TX2 60 mg/L. The zeta potential in the presence of TX2 increases in the order of arsenopyrite > pyrrhotite > marmatite, which is corresponding to the adsorption order of TX2 on the three minerals. Figure 3.33 also suggests that the adsorption of anionic depressant TX2 on negatively charged marmatite, arsenopyrite and pyrrhotite may be due to the chemical interaction. 

Sodium acetate dithio carbonic sodium TXl (NaOOClCHjOCSSNa 196... 

Sodium propronate dithio carbonic sodium TX2 (NaOOClCzILOCSSNa 210... 

The influence of copper ion on the flotation of zinc-iron sulphide minerals in the presence of depressant with butyl xanthate l.Ox 10 mol/L as a collector is presented in Fig. 6.11 to Fig. 6.14. It can be seen from Fig. 6.11 and Fig. 6.12 that in the presence of 120 mg/L 2-hydroxyl ethyl dithio carbonic sodium (GXl) and 2,3 dihydroxyl propyl dithio carbonic sodium (GX2), marmatite is activated by copper ion and exhibits very good flotation with a recovery above 90% in the pH range of 4-8. The flotation of arsenopyrite and pyrrhotite is poor with a... 

Figure 6.13 and Fig. 6.14 demonstrate the flotation results of zinc-iron sulphide minerals with l.Ox lO mel/L butyl xanthate as a collector in the presence of (1-carbonic sodium-2-hydroxyl) sodium propronate dithio carbonic sodium (TX3) or (1-carbonic sodium-2-sodium acetate) sodium propronate dithio carbonic... 

A rapid method of preparation of [Mn(NH20H)2Cl2] has been reported that is easily carried out and does not require the use of hydroxylamine. It involves treatment of manganese(ii) carbonate with hydroxylamine hydrochloride in boiling water. The complexes formed between Mn and tetramethyl- and tetraethyl-dithio-oxamide have been investigated by the Job method MnL3X2 (X = C10 or FeCl4 ) were observed. ... 

The preformation of carbazol-9-ylpotassium (sodium) has been much less used for the introduction of acyl groups onto nitrogen examples are the formation of 9-methoxy- and 9-ethoxy-carbonylcarbazoles, the dithio-carbamate salt 51, and the malonate 52 by reaction with the alkoxy-chloroformates, carbon disulhde, and malonic acid half-acid chloride, respectively. 

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