Subject thiophenolates

Reactions of thiolates with chlorocyclophosphazenes are found to proceed in a geminal pathway. Only very limited thiols such as thiophenol, methyl and ethyl mercaptans have been subjected to these studies (Eq. 24) [80, 81]. 

Reaction systems containing cobalt and nickel were characterized by the production of flocculent precipitates of compounds other than hydroxides in the presence of all thiols, except for thiophenol and tert-butanethiol. Samples of these complexes produced from the ethanethiol system were washed, dried, and subjected to microanalysis. For nickel, the precipitate could be separated into two fractions by extracting with... 

A similar mechanism is thought to be involved when functionalized dihalocyclopropanes are treated with sodium alkoxides as well as thiophenolates or subjected to the influence of potassium hydroxide in methanol. 

There are several examples of this approach to thiophenes. The reaction of thiophenol with acetylene in the vapor phase at 600-650 °C gave benzo[h]thiophene in 71% yield. p-Toluenethiol affords 5-methylbenzo[h ]thiophene in 54% yield under the same conditions (54HC(7)l). The best example of this type of synthesis was the reaction of 3-mercaptocy-clohexanones (235) with glyoxal to form the thiophenes (236), which was the subject of a patent (70USP3511854). The reaction proceeds smoothly under reflux conditions, using ah inert solvent, such as benzene or toluene, which will azeotrope with water, and a protic acid catalyst. A solution of (235) in the solvent is added to 40% aqueous glyoxal solution containing some acid. After reflux the thiophene (236) can be isolated in 70-90% yield. 

The simple rule for the prediction of the possibility of GC analysis of organic compounds is based on the reference data of their boiling points. If any compound can be distilled without decomposition at the pressures from atmospheric to 0.01-0.1 torr, it can be subjected to GC analysis, at least on standard nonpolar polydi-methylsiloxane stationary phases. In accordance with this rule, most of the monofunctional —OH compounds (alcohols, phenols) and their S analogs (thiols, thiophenols, etc.) may be analyzed directly. The confirmation of chromatographic properties of any analytes must be not only verbal (at the binary level yes/no ) but also based on their GC Kovats retention indices as the most objective criteria for example ... 

Regioselective displacement of chlorine from 4,5-dichloro-3(2//)-pyridazinones has been shown to be exceptionally dependent on the solvent and has been the subject of several studies. With 2-methyl and 2-phenyl-4,5-dichloro-3(2//)-pyridazinones as substrates, reaction with alkoxides occurs selectively at C-4 in less polar solvents (carbon tetrachloride, dioxane, THF, t-BuOH, pyridine), is nonselective in solvents of intermediate polarity (acetone, 2-propanol), and is selective for C-5 in polar solvents (EtOH, MeOH, DMF, DMSO) with the exception of acetonitrile, in which mixtures are obtained. Similar selectivity was seen with phenol and ethanethiol, but with thiophenol and ethyl... 

Esterification. DCC has seen little use for esterification because of variable yields, which are satisfactory only in the case of phenols and thiophenols. Pyridine exerts a favorable effect the more effective acylation catalyst DMAP is more useful. With this catalyst, esters and thioesters can be obtained generally in yields of 60-95 7 . Even the hindered 2,4,6-trimethylbenzoic acid can be converted in this way into the methyl ester in yield. However, the method is subject to steric effects for example, adamantqnecarboxylic acid does not react with r-butyl alcohol under these conditions. 

Notes and discussion. This reaction affords the 2-phenyl-, ethyl- and benzyl thioglycosides of sialic acid on exposure to the corresponding mercaptans with enhanced (3-selectivity. In the literature, treatment of the P-penta-0-acetate derivative with thiophenol produces 81% of the P-phenylthioglycoside derivative together with 7% of the a-isomer. In practice, the phenylthioglycoside is prepared from the mixture of a- and P-penta-O-acetates (ratio ca. 1 8), which is subjected to the coupling reaction without fractionation of each isomer. 

In order to obtain isosteric sulfur and selenium analogs of retinyl ethers, the acetoxy group in retinyl acetate (9) was subjected to a nucleophilic substitution reaction with thiophenolate and selenophenolate to give (577) and (578), respectively (Welch and Gruber, 1979). The products were obtained in good yields, and the all-trans configuration was retained. 

General procedure for preparation of 2-amino-4-(phenylthio)-4//-chromene-3-carbonitrile 6 In an oven-dried screw cap test tube, a mixture of sahcyhc aldehyde 1 (1 mmol), malononitrile 2 (1 mmol), thiophenol 5 (1 mmol) and sodium formate (10 mol%) was stirred with 4 mL of ethanol at room temperature for 2-3 h. On completion of the reaction as monitored by TLC, the product was precipitated out and filtered the filtrate was preserved for reuse. The crude residue was subjected to column chromatography using silica gel (60-120 mesh) and petrol ether-ethyl acetate mixture to obtain pure product 6, characterized by analytical and conventional spectroscopic methods. 

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