Aryl xanthates

The dixanthogens derived from the aryl xanthates are reported in Reference 52. 

The in vitro trypanocidal and antitumor activities of lfr(cot)L], cot = cyclotetraene, derivatives of dithiocarbamates and xanthates, have been investigated.700 The Ir complexes were characterized by IR spectroscopy, and MO calculations (Hiickel) were performed on the ligands. Similar studies were performed on [Ir(nbr)L], nbr = norbornadiene, L = derivatives of alquil and aryl xanthates 701 and also on [Ir2(cod)2L]X2, where L = 2-hydroxystilbamidine, X = C1, N03, C104, BPh4, and [Ir(cod)L2 ]X, where L = benznidazole, R0-2516, nifurtimox, niridazole. The complex [Ir2(cod)2(2-hydroxystilbami-dine)](BPh4)2 showed the highest activity, as studied by optical microscopy of rats kidneys. 

Following the successful synthesis of the aryl xanthate complexes, Chen and Fackler reported on the synthesis and structural characterization of the diamagnetic, monomeric bis(0-2,4,6-trimethylphenylxanthato)palladium(II) complex (117). A typical PdS4 unit was found in this complex in which the shorter S2C-0 bond length [1.330(12) A] compared to the Ph-0 bond length [ 1.439(16)] indicates a certain importance of the S2C=6 resonance form in the structure of the xanthate ligand. 

Alkyl xanthates (Rxan) of most elements have been known for a long time.1,40 Aryl xanthates have been prepared via potassium xanthate (of 2-substituted phenols only) and thallium aryl xanthates.92... 

The Leuckart Thiophenol Reaction allows the preparation of thiophenols and corresponding thioethers from anilines or their corresponding diazonium salts. The first step is the reaction of an aryl diazonium salt with a potassium alkyl xanthate to give an aryl xanthate, which affords an aryl mercaptan upon basic hydrolysis or an aryl thioether upon warming. 

Aryl xanthates have been derived in 90% yieid by a phase transfer-catalysed method. The phenol and iodomethane were added to the two-phase system of 50% aqueous sodium hydroxide containing tetra-n-butylammonium bisulphate and carbon disulphide and the mixture stirred vigorousiy for 0.5 hour (ref.24). 

Carbon disulfide reacts with a wide range of bases to produce ligands which readily coordinate to metals. New synthetic work including the formation of aryl xanthates, disulfide products, and oxidized metal dithiolates is reviewed. The sulfur addition and abstraction reactions are discussed, along with the photobleaching reaction of [Ni(n-butyldtc)a] Bridged mercaptide complexes of nickel triad elements are also described. 

Aryl Xanthates. It is 165 years since Zeise (8) reported the formation of xanthates from alcohol and CS2 on reaction with base. Yet only three papers, a 1948 Itahan patent (9), a 1970 report by Lee (10), and a recent (1971) report by Reichle (11), relate to the synthesis of aryl xanthates. We established (12) that the Italian patent is incorrect. 

Lee (JO) first synthesized an aryl xanthate by reacting thallous phenoxide with CS2 in benzene (Reaction 2). Reichle 11) synthesized... 

The general synthesis of aryl xanthates is described by Schussler et al. 12). It follows from the ability of thallium(I) xanthates to undergo metathetical reactions with metal halides in absolute ethanol (Reaction 4). The thallium(I) precursors could be obtained with phenol... 

The physical properties of these aryl xanthates resemble closely those of their alkyl counterparts. The thallium compounds are heat- and light-sensitive, and they decompose in acetone or THF to form TI2S, TP,... 

There has been a review of the use of transition-metal catalysts in the formation of C—S, C—Se, and C—Te bonds." Copper catalysis enables the formation of unsymmetrical diaryl thioethers from two differently substituted aryl iodides using ethylxanthogenate as the source of sulfur. Initial formation of an aryl xanthate, such as (17), is followed by hydrolysis to the arenethiolate, which couples with the second aryl iodide." Copper catalysis has also been used in the methylthiolation of aryl halides by DMSO. The method requires the presence of a source of fluoride ions, such as zinc fluoride." In the presence of a palladium catalyst, the reaction of aryl and heteroaryl bromides with AgSCp3 gives the corresponding trifluoromethylsulfldes." ... 

Decomposition of diazoxanthates, by warming gently in faintly acidic cuprous media, to the corresponding aryl xanthates which afford aryl thiols on alkaline hydrolysis and aryl thioethers on warming ... 

Aryl xanthates mainly comprise phenmethyl and cinnamyl xanthates. Benzyl alcohol xanthate can be prepared from benzyl alcohol ... 

Table 1.1 Flotation results of copper ore with aryl xanthates (reagent dosage 100 g/t)...

Table 1.2 Comparison of aryl xanthate and alkyl xanthate in the flotation of copper ore...

N-dialkyl dithiocarbamates, electron-withdrawing substituents on Z can enhance the activity of RAFT agents so that they are more effective in polymerization of styrenic and (meth) acrylic monomers. Thus transfer coefficients of the 0-aryl xanthates are higher than those of simple 0-alkyl xanthates. Those of fluorinated xanthates (158 and 159) are higher than those of nonfluorinated analogs (160 and 166, respectively). 

In the case of O-alkyl xanthates, the choice of the alkyl is cmcial. It is important that the alkyl on oxygen is a very poor homolytic leaving group with respect to the alkyl group on sulfur for cleavage of the S-R bond to be favored over cleat ge of the O-alkyl bond. For example, control (predicted Ad , low Af /Afn) can be obtained in RAFF polymerization with O-methyl, O-ethyl (170), O-isopropyl, and O-aryl xanthates but not with the O-tert-butyl xanthate. ... 

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