Thiones olefination

Monothioacetals 1,3-Oxathiolanes Thiolactams S extrusion, 59-60, 261 Thiols synthesis from haloalkanes, 169, 269 Thionation of lactones, 110-111 Thiones olefination of, 35 Thionocarbonates. See Carbonothioates Thionolactones, 110-111 Thionyl chloride prepn. of acyl halides, 143 prepn. of carboxylic esters, 347 prepn. of haloalkanes from alcohols, 32 Thiophenoi. See Benzenethiol Thiotosylatc. See Benzenesulfonothioic add... 

The problem of the synthesis of highly substituted olefins from ketones according to this principle was solved by D.H.R. Barton. The ketones are first connected to azines by hydrazine and secondly treated with hydrogen sulfide to yield 1,3,4-thiadiazolidines. In this heterocycle the substituents of the prospective olefin are too far from each other to produce problems. Mild oxidation of the hydrazine nitrogens produces d -l,3,4-thiadiazolines. The decisive step of carbon-carbon bond formation is achieved in a thermal reaction a nitrogen molecule is cleaved off and the biradical formed recombines immediately since its two reactive centers are hold together by the sulfur atom. The thiirane (episulfide) can be finally desulfurized by phosphines or phosphites, and the desired olefin is formed. With very large substituents the 1,3,4-thiadiazolidines do not form with hydrazine. In such cases, however, direct thiadiazoline formation from thiones and diazo compounds is often possible, or a thermal reaction between alkylideneazinophosphoranes and thiones may be successful (D.H.R. Barton, 1972, 1974, 1975). 

In the cationic intermediate (180), when the steric interaction between R, and R2 becomes too great, Ri is eliminated as an olefin leaving the nitrogen-unsubstituted A-4 thiazoline-2-thione (182). 

By application of the Corey-Winter reaction,vicinal diols 1 can be converted into olefins 3. The key step is the cleavage of cyclic thionocarbonates 2 (1,3-dioxolanyl-2-thiones) upon treatment with trivalent phosphorus compounds. The required cyclic thionocarbonate 2 can be prepared from a 1,2-diol 1 and thio-phosgene 4 in the presence of 4-dimethylaminopyridine (DMtVP) ... 

The formation of thietanes from thiones and olefins has been less exploited for synthetic purposes than the corresponding oxetane-forming reaction. It should be remarked that thiocarbonyl compounds very often undergo efficient photoreactions from the second excited singlet state S2 U4). One interesting synthetic application is found in the photochemical preparation of quinolines from N-thioamides (4.84)498). The primary photochemical step is assumed to be the intramolecular thietane formation. 

Kaiser and Wulfers reported the first example of a thietane formation reaction involving photolysis of thiobenzophenone with olefins [27]. Since then a large number of systems have been reported. Thiobenzophenone and related compounds, xanthione and related compounds, the a,p-unsaturated thiones such as thiocoumarin, and adamantanethione have been most thoroughly examined. The wavelength dependence of these reactions has been systematically investigated in order to ascertain differences, if any, in the photochemistry of the thione S2 and T states. Scheme 1 shows one example of photocycloaddition of... 

The highly substituted derivative 186, in the form of the potassium salt, has been recommended for use in detonators in place of the more dangerous mercury fulminate. l,2,3-Benzotriazine-4-thione (39, R — H) has been used in photographic transfer emulsions as an inhibitor and toning agent, and heavy metal salts of the oxygen analog 10, R = H are employed as photodevelopable emulsions. The latter compound is also claimed to be useful as a stabilizer in olefin polymers and as an antioxidant in certain other polymers. Dimeric derivatives of 10 have... 

Photocycloaddition of thiones to alkenes is the most popular and fruitful method for the preparation of the thietane system. In analogy to the formation of the oxetanes by cycloaddition of the electronic excited ( ,tc ) carbonyls, thietanes can be expected to arise photochemically from aromatic thioketones and substituted olefins as well as 1,2- and 1,3-dienes. ° Thiobenzophenone serves as a source of a sulfur atom and, because of its blue color, which disappears on photocycloaddition, permits exact control over the reaction time. A mixture of thiobenzophenone and a-phellandrene must be irradiated for 70 hr before the blue color disappears (Eq. 2) and... 

Electron-rich and electron-poor olefins influence the outcome of the thietane reaction. Olefins containing electron-withdrawing groups react only with the n,n state of the thiones to produce the four-membered S-ring (Eq, 110 jjjg mechanism is described as an electron transfer from... 

With electron-rich olefins, the rate of addition to a second thione is faster than that of the combination of the intermediate diradical to thietane. By substituting these olefins, however, with groups that provide steric hindrance, the reaction of the diradical with another thione molecule can be inhibited. Irradiation of thiobenzophenone and 1,3-cyclooctadiene, propenylbenzene. 

Irradiation of thiones with 589-nm light in the presence of electron-deficient olefins produced 99 and 100. By-product 89 is the result of an ortho attack on the benzene ring. 

Studies with other thiocarbonyl compounds reveal a different reactivity pattern from that of thiones in the presence of olefins. 0-Alkyl thiobenzoates do not form dithiane products. Instead, if an olefin carries no bulky substituents, the intermediate diradical cyclizes directly to the thietane ring (Eq. 4). The excited (n, 71 ) state of thiophosgene reacts with alkenes to... 

Other variants that are used in lubricating oils are sulfurized olefin compositions (69). An example for poly(isobutyl-l,2-dithiol-e-4-cyclopentene-3-thione) compounds is shown in Figure 6.10. 

Preparative methods and chemical properties of tetrazole-5-thiones (tetrazole-5-thiols) have been summarized in a review <2004RJ0447>. The most significant results in this field were obtained in the last decade while studying the alkylation of tetrazole-5-ylthiones (tetrazole-5-ylthiols), and the oxidation of 1-substituted 5-alkylsulfatetrazoles to the corresponding sulfinyl and sulfonyl derivatives. Special attention should be paid to the Kocienski-modified Julia olefination based on the application of 5-alkylsulfonyltetrazoles to the activation of chemical reactions. 

The enamino thione 221 adds electrophilic olefins 222 (R = CN or C02Me) to yield dihydrothiapyrans 223, which eliminate the amine moiety on heating to form 2H-thiapyrans 224 (equation 93)115. 

On the other hand, protic (and anionic) nucleophiles (Nu = 0-, N <, S-, CN) readily add across the exocyclic olefinic bond Enehydrazine 15 (R = Ph, X = S) furnishes a number of 5-Nu-substituted 1-phenylami-noimidazolidine-2-thiones 19 (Scheme 3). Similarly, 16 (X = O) can be converted into 5-Nu-substituted l-arylaminoimidazolidin-2-ones. Some electrophiles react with enehydrazine 16 (e.g., R = Bn, X = O) at the... 

Reviews have appeared of the solid-state dimerisation of thiones, the photooxidation of sulphur compounds, thiocarbonyl photochemistry, the DCA sensitized photooxygenation of olefins, and of the role of intersystero crossing steps in singlet oxygen chemistry. ... 

Detailed information is available on certain compound types, for example, on thiophene (94), thiols (101), thiols and thions (86), mercaptans, hydrogen sulfide and olefin reactions (96), sulfenic acids (98), sulfides and sulfones (106), sulfides and disulfides (100) ... 

Recently, another cobalt(II)/camphor-derived complex was developed for performing the asymmetric cyclopropanation of olefins [38]. The complex 18 was prepared by reacting the ligand 17, synthesized by condensation of (lR)-3-hydroxymethylenebornane-2-thione and the corresponding diamine, with co-balt(II) dichloride hexahydrate in degassed ethanol (Scheme 11). The cyclopropane derivatives were obtained in 50-60% yield using 3 mol % of the catalyst 18 and ethyl diazoacetate in styrene or 1-octene as solvent. The diastereomeric ratios were low for both styrene and 1-octene. 

A series of stabilized and isolable o-thiobenzoquinone methides and related o-thioquinone methides, initially prepared by the photochemical addition of olefins to 1,2-benzodithiole-3-thione [Eq. (15)],33 34... 

An interesting and reactive class of 4ir thiabutadienes capable of useful participation in normal (HOMOd,ene controlled) Diels-Alder reactions are the stable thioacylketene thioacetals, generated by the photoaddition of olefins to I,2-dithiole-3-thiones [Eq. (10)]. 

---