Alkyl dithio

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. 

The same research group <1994JPR266> expanded the synthesis to encompass diamidinium salts. Using dithioether spacers between amidine units, three alkyl-dithio-bis(l,2,3,5-dithiadiazolium) salts were synthesized (compounds 61-63), from the respective diamidine salts (Equation 8), in yields of 90%. 

Ransac, S., Gargouri, Y, Moreau, H. and Verger, R. (1991) Inactivation of pancreatic and gastric lipases by tetrahydrolipstatin and alkyl-dithio-5-(2-nitroben-zoic acid). A kinetic study with 1,2-dide-canoyl-sn-glycerol monolayers. Eur. ]. 

Mixed alkyl/dithio- or diselenocarbamates are potential precursors to II-VI materials as they provide access to lower deposition temperatures. Zinc selenide, cadmium sulfide, and cadmium selenide thin films have been deposited from compounds of the type [RM(E2CNEt2)]2 (79, M = Zn, E = S, R = Me 80, M = Cd, E = S, R = Me 81, M = Cd, E = Se, R = Me 82, M = Cd, E = S, R = CH2CMe3 83, M = Cd, E = Se, R = CH2CMe3). The films were superior and higher growth rates were obtained as compared with those... 

More recently, widespread use has been made of optical rotatory dispersion as a means for studying configurations. a-Amino acids were investigated as such or as derivatives, notably alkyl dithio-carbamates (116) , copper(n) complexes , and cobalt(m) complexes . From these studies useful though not always straightforward correlations have been obtained, between the shape and location of the dispersion curves and the configuration of the compounds. 

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],... 

Dithio-l-nitroalkenes are prepared by the reacdon of nitromethane v/ith CS and KOH followed by alkyladonv/ith alkyl halides CEq. 10.84. They are important reagents forsynthesis... 

The salts of alkyl xanthates, A/,A/ -di-substituted dithio-carbamates and dialkyidithiophosphates [26] are effective peroxide decomposers. Since no active hydrogen is present in these compounds, an electron-transfer mechanism was suggested. The peroxide radical is capable of abstracting an electron from the electron-rich sulfur atom and is converted into a peroxy anion as illustrated below for zinc dialkyl dithiocarbamate [27] ... 

In contrast, a-ketosulphoxides react with isocyanates to give the products of a monoaddition only550 (equation 290). Reaction of dimsyl anion with trithiocarbonates 481 followed by alkylation results in the formation of (methylsulphinyl)ketene dithio-acetals 482551 (equation 291). 

The nickel(II) dithiocarbamate complexes are neutral, water-insoluble, usually square-planar, species, and they have been studied extensively by a range of physical techniques. The usual methods for the synthesis of dithiocarbamate complexes have been employed in the case of Ni(II), Pd(II), and Pt(II). In addition, McCormick and co-workers (330,332) found that CS2 inserted into the Ni-N bonds of [Ni(aziri-dine)4P+, [Nilaziridinelgf, and [Ni(2-methylaziridine)4] to afford dithiocarbamate complexes. The diamagnetic products are probably planar, but they have properties typical of dithiocarbamate complexes, and IR- and electronic-spectral measurements suggested that they may be examples of N,S-, rather than S,S-, bonded dithiocarbamates. The S,S-bonded complexes are however, obtained, by a slow rearrangement in methanol. The optically active lV-alkyl-iV(a-phenethyl)dithio-carbamates of Ni(II), Pd(II), and Cu(II) (XXIV) have been synthesized, and the optical activity was found to be related to the anisotropy of the charge-transfer transitions (332). 

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). 

In all cases, dithio-phosphorus acids can be liberated from their alkali-metal salts by reacting them with acids such as HC1. Thio-ester derivatives of the dithio-phosphorus acids can be synthesised via reaction of the acids themselves with an alcohol or phenol (Equation 26) or from reaction of their alkali-metal salt with an alkyl halide (Equation 27). 

Pappalardo and co-workers studied the mass spectral characteristics of alkyl and aryl substituted 2,5-dithio-1,3,4-thiadiazoles. Selected ions in the mass spectra of SH, S-CH3, and S-aryl thiadiazoles were tabulated. The S-aryl thiadiazoles form stable cyclic ions yielding additional fragments. The fragmentation pattern is dependent on the structural characteristics of the substituents. If both tautomers—thiol and thione—are present, the molecular ion will also lose CS2. Besides the base peak, intense peaks observed in the MS spectrum are due to extensive fission of the thiadiazole ring. Some of the fragments formed are shown in Scheme 4 <820MS(17)335). 

Numerous complexes of nickel(II) with phosphorodithioate ligands (also called dithio-phosphates 280 R — R" = 0-alkyl, O-aryl) and dithiophosphinates (280 R = R" = alkyl, aryl) have been reported to date. A few dithiophosphonato complexes (280 R = alkyl, R" = O-alkyl) were also reported. The bis(dialkyldithiophosphato)nickel(II) complexes were obtained as purple diamagnetic compounds by means of the direct synthesis between the appropriate dithioacid (RO)2P(S)SH and a nickel(II) salt, often the acetate hydrate. The dithioacid can be conveniently prepared in situ, by reacting P4Si0 with the appropriate alcohol which sometimes acts by itself as reaction medium. Structural properties of selected nickel(II) complexes are reported in Table 90. 

Isothioureas can be prepared on insoluble supports by S-alkylation or S-arylation of thioureas (Entry 7, Table 14.6). Further methods for the preparation of isothioureas on insoluble supports include the N-alkylation of polystyrene-bound, A/,/V -di(alkoxy-carbonyl)isothioureas with aliphatic alcohols by Mitsunobu reaction (Entry 7, Table 14.6) and the addition of thiols to resin-bound carbodiimides [7]. Resin-bound dithio-carbamates, which can easily be prepared from Merrifield resin, carbon disulfide, and amines [76], react with phosgene to yield chlorothioformamidines, which can be converted into isothioureas by treatment with amines (Entry 8, Table 14.6). The conversion of support-bound a-amino acids into thioureas can be accompanied by the release of thiohydantoins into solution (see Section 15.9). The rate of this cyclization depends, however, on the type of linker used and on the nucleophilicity of the intermediate thiourea. 

Scheme 1. Reduction of homodimer peptide linked via a disulfide bridge with dithio-threitol (DTT) and alkylation of the resulting thiol groups of both cysteines with either acrylamide (upper reaction) or iodoacetamide (lower reaction).

Carbon disulfide is the dithio derivative of C02. It is only a weak electrophile. Actually, it is so unreactive that in many reactions it can be used as a solvent. Consequently, only good nucleophiles can add to the C—S double bond of carbon disulfide. For example, alkali metal alkoxides add to carbon disulfide forming alkali metal xan-thates A (Figure 7.4). If one were to protonate this compound this would provide compound B, which is a derivative of free dithiocarbonic acid. It is unstable in the condensed phase in pure form, just as free carbonic acid and the unsubstituted carbamic acid (Formula B in Figure 7.3) are unstable. Compound B would therefore decompose spontaneously into ROH and CS2. Stable derivatives of alkali metal xanthates A are their esters C. They are referred to as xanthic add esters or xanthates. They are obtained by an alkylation (almost always by a methylation) of the alkali metal xanthates A. You have already learned about synthesis applications of xanthic acid esters in Figures 1.32, 4.13, and 4.14. 

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