Thiolene oxides

Two attractive routes to thiolene oxide and dioxide are the diene-SO104 and diene-S02298 cycloadditions, respectively. These cycloadditions are highly stereoselective at both carbons of the diene systems and at sulfur (see equation 62 for specifics) which, in the case of sulfoxide formation, proceed via attack of triplet SO on the diene. Equation 112 shows an example of such a cycloaddition104. The overall yields are significantly improved by running the cycloadditions in the absence of oxygen and by the use of excess diene. 

Since sulfoxides and sulfones are versatile synthetic intermediates, and since in both the thiolene oxide and dioxides the reverse dethionylation114 ( — SO), and cheletropic extrusion of sulfur dioxide296, respectively, readily take place thermally, these cycloadditions are expected to find a useful place in organic synthesis. It should be kept in mind, however, that the retrograde SO-diene reaction and interconversion of the thiolene oxides compete effectively against SO extrusion on heating, and that diene isomerization accompanies the forward reaction (SO + diene). 

Thiolane oxides, Thiolene oxides, Thiophene oxides... 

Thio-Claisen rearrangement 746-748 Thioketene 5-oxides photolysis of 878 reactions of 277 Thiolane dioxides formula of 382 NMR spectra of 460 reactions of 604 synthesis of 461 Thiolane oxides 747 formula of 382 IR spectra of 461 synthesis of 461, 462, 752 Thiolanes, photolysis of 881 Thiolene dioxides formula of 382 NMR spectra of 460 reactions of 464, 465 synthesis of 461 Thiolene oxides formula of 382 synthesis of 461, 746 Thiols... 

Thus the reaction of the three geometrical isomers of 2,4-hexadiene with thiirane oxide afforded the three related 3-thiolene 5-oxides 154 depicted in equation 62104... 

Fluorination of tetrachlorothiophene with potassium tetrafluorocobaltate(III) gave 3,4-dichlorotetrafluoro-3-thiolene (156). Similar fluorination of thiophene yielded the 3-thiolene (157) and the thiolan (158) <71JCS(C)346, 72T43). It has been suggested that the fluorination proceeds by initial oxidation of thiophene to the cation-radical by the metal ion, and subsequent quenching of this by atomic fluorine (Scheme 30). 

Unsubstituted 3-hydroxythiophene is less stable than 2-hydroxythiophene (63AHC(l)l). This instability may be due to oxidative coupling. In order to confirm this, 2,5-dimethyl-3-hydroxythiophene was subjected to ferricyanide oxidation (72ACS31). Racemic and meso forms of 2,2, 5,5 -tetramethyl-bi-4-thiolen-3-one (445) were isolated. When the a-substituent was r-butyl instead of methyl, exposure to air gave 2-(2,5-di-r-butyl-4-thiolen-3-one) 3-(2,5-di-r-butylthienyl) ether (446), formed by carbon-oxygen coupling. 

The two parts of the present volume contain seventeen chapters written by experts from eleven countries. They cover computational chemistry, structural chemistry by spectroscopic methods, luminescence, thermochemistry, synthesis, various aspect of chemical behavior such as application as synthons, acid-base properties, coordination chemistry, redox behavior, electrochemistry, analytical chemistry and biological aspects of the metal enolates. Chapters are devoted to special families of compounds, such as the metal ynolates and 1,2-thiolenes and, besides their use as synthons in organic and inorganic chemistry, chapters appear on applications of metal enolates in structural analysis as NMR shift reagents, catalysis, polymerization, electronic devices and deposition of metals and their oxides. 

Five membered ring sulfones (thiolene-1, 1-dioxides, sulfolenes or dihydrothiophene-1, 1-dioxides) can be obtained by peracid oxidation of tetrahydrothiophene. The extrusion of sulfure dioxide from dihydrothiophene-1,1 dioxides or sulfolenes like (178) has been much studied as it provides a synthetic route to dienes, e.g. butadiene (152) (Scheme 70). The reverse reaction provides a method of synthesis of sulfolene (178) from butadiene (152) and sulfur dioxide. Thiolene dioxides or sulfolenes can be generally prepared by addition of sulfur dioxide to conjugated dienes for example, 1,4-dimethylbutadiene (179) in the presence of sulfure dioxide, triethylamine and formic acid affords 2,5-dimethylsulfolene (180) (Scheme 71). 

Diphenylthiirene 1-oxide (29) reacts with a-lithioisobutyronitrile to yield 5-imino-4,4-dimethyl-2,3-diphenyl-2-thiolene 1-oxide in 90% yield via nucleophilic attack of the carbanion to the ring carbon of (29) followed by recrystallization of the resulting sulfenic acid intermediate (Scheme 10) <87NKK1393>. 

These compounds are much more difficult to handle and much less accessible than phenols. Neither 2-hydroxythiophene nor its 4-thiolen-2-one tautomer are detectable, the compound existing as the conjugated enone isomer, 3-thiolen-2-one, which can be obtained directly by oxidation of thiophene. ... 

Dicarboxylic Acids.— Perfluoro- -thiaglutaric add has been obtained by permanganate oxidation of fluorinated thiolens (10 X == Y = H X = H, Y = F X = Y = F X = Y = Cl) procured in studies of the fluorination of tetrachlorothiophen, thiophen, and tetrahydrothiophen with cobalt trifluoride, manganese trifluoride, and potassium tetrafluorocobaltate(m). The best route to this acid still appears to be fluorination of tetrachlorothiophen with silver difluoride followed by permanganate oxidation of the 3,4-dichlorotetrafluoro-3-thiolen (10 X = Y = Cl) thus obtained in not less than 45% yield. ... 

Permanganate oxidation of 3,4-dichlorotetrafluoro-3>thiolen, prepared by fluorination of tetrachlorothiophene with silver diiluoride, yields the sulphur analogue S(CFa-CO,H)j of periluoro-oxydiacetic acid."... 

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