Thioethers reactions

The cyclic polythioether complex [W(CO)4L] (L = 2,5,8,ll-tetrathia[12](2,5)thiophenophane was prepared by UV irradiation of [W(CO)6] in the presence of the ligand in thf. Variable-temperature H NMR studies showed that this species was fluxional, and the derived molecular structure indicated k -L-S S coordination (17). The thioether-bridged complexes [ W(CO)4)2T] (18), where L is the hexakis(alkylsulfanylmethyl)benzene, C6(CH2SR)6 (R = C5H11, Pr ) were obtained by reaction of [W(CO)4(NCMe)2] with the appropriate thioether. Reaction of [W(CO)4(tmpa)] (tmpa = V,iV,iV, iV -tetramethyl-l,3-propanediamine) with 1,5-diselenacyclooctane ([8]aneSe2) gave the cis-disubstituted produce [W(CO)4 [8]aneSe2 ]. 

The reaction of oxiranes with thiols permits the preparation of a-hydroxyalkyl thioethers. Reactions with thiophenols are presented in Eqs. 306 and 307.1 ... 

These results can be explained by the relative rates of the formation of the sulfoxide (step a) and of the corresponding sulfone (step b) in the oxidation reaction of thioethers (reaction 1). It is known that, for dialkyl sulfides, such as Et2S, Pr2S and BU2S, sulfoxide formation proceeds much faster than sulfone formation [1], For the allyl sulfide the selectivity in sulfoxide is lower, because the difference in the rates of the two steps (a) and (b) of the oxidation reaction is less important, due to the conjugation of the lone electron pairs on the sulfur atom with the unsaturated system [1],... 

The sterically relatively open carbonyl group at C3 is significantly more reactive than its hindered counterpart at 20-Reaction of 16-dehydroprogesterone (1-4) with benzenethiol takes a different course at the two conjugated ketones present in the compound. Reaction at C3 proceeds to form an enol thioether reaction with the unsaturation in ring D, on the other hand, consists of conjugate addition of the thiol at a distance from the hindered carbonyl (6-1) (Scheme 6.6). 

The 1-proton in 1,3-dienyl ethers and -thioethers is expected to be more acidic than that in vinyl ethers and vinyl sulfides, because the outer double bond is likely to exert some electron-withdrawing influence. However, addition of the base (in a conjugate fashion) will also be more facile than with the simple vinyl ethers and -thioethers. Reaction of 1-methylthio-l,3-butadiene with butyllithium or butyl-lithium. TMEDA in THF has been shown to result in conjugate addition [91]. The... 

Figure 3-17. Consecutive application of two reaction schemes to model the oxidation of thioethers to sulfoxides.

Clearly, for symmetry reasons, the reverse process should also be considered. In fact, early versions of our reaction prediction and synthesis design system EROS [21] contained the reaction schemes of Figures 3-13, 3-15, and 3-16 and the reverse of the scheme shown in Figure 3-16. These four reaction schemes and their combined application include the majority of reactions observed in organic chemistry. Figure 3-17 shows a consecutive application of the reaction schemes of Figures 3-16 and 3-13 to model the oxidation of thioethers to sulfoxides. 

Preparation of 2 4-dinitrophenyl-sulphides. Dissolve about 0-5 g. (or 0 005 mol) of the mercaptan in 10-15 ml, of rectified spirit (or in the minimum volume necessary for solution warming is permissible) and add 2 ml. of 10 per cent, sodium hydroxide solution. Mix the resulting sodium mercaptide solution with a solution of 1 g. of 2 4-dinitrochlorobenzene in 5 ml. of rectified spirit. Reaction may occur immediately with precipitation of the thioether. In any case reflux the mixture for 10 minutes on a water bath in order to ensure the completeness of the reaction. Filter the hot solution rapidly allow the solution to cool when the sulphide will crystaUise out. RecrystaUise from alcohol. 

Halide derivatives may be fluorides, chlorides, or bromides. Fluorides are best prepared by the reaction of hydroxy groups with (diethylamino)sulfur trilluoride ( DAST M. Sharma, 1977) or of glycosyl thioethers with DAST/NBS (K.C. Nicolaou, 1990 B). The other halides are usually only introduced at the glycosidic position, where treatment with hydrogen chloride... 

The nucleophUic reactivity in neutral medium has been used extensively to prepare various thioethers of thiazole (122). In acidic medium, alkylation may be performed with alcohols (123, 124). An unexpected reaction encountered was the decarboxylation of 2-mercapto-4-methyl-5-thiazolecarboxyhc acid (60) when treated with butyl alcohol under acidic conditions (Scheme 27) (123). Reaction between A-4-thiazoline-2-thione... 

Thioethers can be obtained either by heterocyclization (Chapter II) or from the reaction between 2-halothiazoles (102) and the sodium salt of... 

Thioethers (105) have also been reported as main products in the reaction between 2-lithium thiazolyl (103) and bis(3-methylbut-2-enyl)-disulhde (104) (Scheme 53) (268). 

Replacement of Boron by Sulfur and Selenium. Trialkylboranes are cleaved by dialkyl- and diaryldisulfides in an air-catalyzed radical reaction producing mixed thioethers (259). 

The reaction of aliphatic and aromatic mercaptans with aziridines yields thioethers (117—119). 

The reaction of thioethers with ethyleneimine in the presence of acid yields sulfonium compounds. The reaction is reversible under alkaline conditions (125). Compounds in which double-bonded sulfur can exist in tautomerism with a form having a free SH group, such as thiourea (126,127), thiocarboxyhc acids (128), and thiophosphates (129), react to give aminoaLkylated products. The P-aminoethyl thiocarboxylate rearranges to give the amide. 

Phthalocyanine sulfonic acids, which can be used as direct cotton dyes (1), are obtained by heating the metal phthalocyanines in oleum. One to four sulfo groups can be introduced in the 4-position by varying concentration, temperature, and reaction time (103). Sulfonyl chlorides, which are important intermediates, can be prepared from chlorosulfonic acid and phthalocyanines (104). The positions of the sulfonyl chloride groups are the same as those of the sulfonic acids (103). Other derivatives, eg, chlormethylphthalocyanines (105—107), / /f-butyl (108—111), amino (112), ethers (109,110,113—116), thioethers (117,118), carboxyl acids (119—122), esters (123), cyanides (112,124—127), and nitrocompounds (126), can be synthesized. 

Deall lation. Chloroformates such as vinyl chloroformates (40) are used to dealkylate tertiary amines. Chloroformates are superior to the typical Von Braun reagent, cyanogen bromide, because of increased selectivity producing cleaner products. Other chloroformates such as aHyl, methyl, phenyl, and trichloroethyl have also been used in dealkylation reactions. Although the dealkylation reaction using chloroformates is mostiy carried out on tertiary amines, dealkylation of oxygen or sulfur centers, ie, ethers or thioethers, can also be achieved. a-Chloroethyl chloroformate [50893-53-3] (ACE-Cl) (41,42) is superior to all previously used chloroformates for the dealkylation reaction. ACE-Cl has the advantage that the conditions requked for ACE... 

The classical structures of pyrrole, furan and thiophene (31) suggest that these compounds might show chemical reactions similar to those of amines, ethers and thioethers (32) respectively. On this basis, the initial attack of the electrophile would be expected to take place at the heteroatom and lead to products such as quaternary ammonium and oxonium salts, sulfoxides and sulfones. Products of this type from the heteroaromatic compounds under consideration are relatively rare. 

Pyrrolethiols, readily obtained from the corresponding thiocyanates by reduction or treatment with alkali, rapidly oxidize to the corresponding disulfides. They are converted into thioethers by reaction with alkyl halides in the presence of base. Both furan- and thiophene-thiols exist predominantly as such rather than in tautomeric thione forms. 

Experiments with cyclic thioethers (80JCS(P1)1693), thiourea, thiocyanate and ethyl xan-thate always led to destruction of oxaziridines (73AJC2159). Products of complicated consecutive reactions could be isolated but only with some difficulty, e.g. (92) from a reaction with carbon disulfide (74JOC957), and (93), obtained by trapping with butadiene a product of a reaction between an oxaziridine and a thiirane (80JOC1691). 

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