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Diketones, reaction with sulfur preparation

Julid investigated the behavior of terfuran 22 and bis(thienyl)furan 23 by cyclic voltammetry as well as the EPR spectra of the radical cations derived from these two compounds. Condensation of the diketone 20 with sulfuric acid furnished furan 22 in 18% yield, while reaction of diketone 21 with hydrochloric acid produced 23 in 84% yield.In a related report, Luo prepared oligomeric bis(thienyl)furans via similar methodology. ... [Pg.170]

These methods are limited in scope. Direct thiation has been reported for the transformation of vicinal diketones to [3,4]-annelated thiophenes <1996CHEC-II(7)49>. Thionations and selenations of vicinal halomethyl ketones with thioacetamide or iV,iV-diethylselenopropionamide as sulfur and selenium donors, respectively, have also been reported <1996CHEC-II(7)49>. In a recent example, thieno[3,4-f]pyrazoles 160 were readily prepared from aryl 5-bromomethyl-l//-l-phenylpyrazole-4-yl ketones 159 by reaction with thioacetamide (Equation 35) <1998JHC71>. Additionally, an example of an amination cyclization by reaction of 161 with benzylamine to afford pyrrolo[3,4-i/ thiazole 162 has been described (Equation 36) <1998JHC71>. [Pg.98]

A modified procedure for the preparation of pyrazoles includes the solventless condensation of diketones and hydrazines in the presence of a catalytic amount of sulfuric acid at ambient temperature <2004GC90>. 1,3-Diketones can be synthesized directly from ketones and acid chlorides and then converted in situ into pyrazoles by the addition of hydrazine <2006OL2675>. The possible modifications to the 1,3-dioxo component in the reaction with hydrazines include the use of -ketoesters, -ketonitriles, -halocarbonyl compounds, -hydroxyketones, -sulfonylketones, and 1,3-dihaloalkanes . [Pg.715]

Diketones. This alkylation of ketimines has been extended to the synthesis of 1,4-diketones by use of a 2,3-dihalopropene as the alkylating reagent. The reaction is carried out with the carbanion, prepared as described above and then diluted with IHF at -60°. The resultant vinylic halide is then hydrolyzed with sulfuric acid at -20 to 0°. [Pg.332]

Protection of 1,2-diols. These reagents are prepared from the diketones and HC(OMe)j in methanol containing a little sulfuric acid. By an acid-catalyzed exchange reaction, 2,3-dimethoxy-l,4-dioxane derivatives are formed in the reaction with 1,2-diols. Diequatorial diols are selectively protected. Actually, the protection can be performed directly by the reaction of a 1,2-diol with an a-diketone, trimethyl orthoformate, in methanol in the presence of camphorsulfonic acid. ... [Pg.331]

Similar reactions may occur with 1,3-diketones and 1,3-diketonates, and these reactions have been exploited by co-ordination chemists to prepare novel sulfur containing chelating ligands. The metal-directed reactions are synthetically useful since it is not possible to prepare 1,3-dithioketones by direct reactions of free 1,3-diketones with hydrogen... [Pg.60]

The sulfenylation of metalloimines is equally applicable to ketones, although using more reactive sulfur electrophiles it is possible to bring about reaction on the unmetallated enamine. ° Sulfenylation of ketone enol silyl ethers also proceeds well with the more reactive sulfur species. Sulfenamides and their derivatives e.g. 11) are particularly suited to the direct sulfenylation of ketones and active methylene compounds such as -diketones, -keto esters and malonates, which undergo facile reaction at room temperature (equation 5). This procedure, however, does not appear to have been exploited for the dehydrogenation of active methylene compounds icf. Section 2.2.4.1). By preparing the dianion (13)... [Pg.125]

When urea (or thiourea) reacts with a-hydroxy ketones or a-diketones the products are imidazolin-2-ones (or -thiones) (70AHC(12)103,66RCR122). The reaction is limited to the preparation of 4,5-alkyl(or aryl)- or l,4,5-trialkyl(or triaryl)-imidazoles since an oxygen or sulfur function appears at C-2. Benzoin condenses with iV-phenylthiourea in hexanol in the presence of catalytic quantities of HCl to give l,4,5-triphenylimidazoline-2-thione (131) in 50-60% yield (Scheme 69). While 1-methylurea can also take part in the reaction. [Pg.481]

A more versatile reducing agent is samarium diiodide, which promotes chemoselective cyclizations of functionalized keto aldehydes in a stereodefined manner to form 2,3-dihydrocyclopentane carboxylate derivatives in good yields and with diastereoselectivities of up to 200 1 (equation 38)7 The reaction proceeds via selective one-electron reduction of the aldehyde component and subsequent nucleophilic attack on the ketone moiety. Stereochemical control is established by chelation of the developing diol (19) with Sm " " which thereby selectively furnishes cis diols (equation 39). The stereoselective M/-cyclization of 1,5-diketones to cis cyclopentane-1,2-diols using TiCU/Zn has been used to prepare stereodefined sterically hindered acyclic 1,2-diols when a removable heteroatom, such as sulfur or selenium, is included in the linking chain (equation 40). [Pg.574]

The diketone (3) Is a versatile intermediate for the preparation of 9-thiabicyclo[3.3.1]nonane derivatives and provides a simple synthetic entry to a number of other heterocycles such as the 2-thiaadamantane. 3 4 thiacyclohexane, thiacycloheptane, 2,6-dlthiaadamantane, 6 and 2-thiabrexane 7 ring systems. Only one previous procedure for Its preparation has been published. This method involves the oxidation of diol (2) with chromium trioxide in pyridine and diohioromethane to yield 9-thiabicyclo[3.3.1]nonane-2,6-dione (3) in 65% yield. In practice this reaction Is difficult to carry out reproducibly because of precipitation of tarry chromium salts which make adequate stirring and extraction of the product very difficult. Consequently the dione (3) is often accompanied by partly oxidized material and/or material where the sulfur atom has been oxidized. The method reported here avoids these technical difficulties and affords a considerably Increased yield. [Pg.64]

This reaction was first reported by Baumann and Fromm in 1891. It is the synthesis of 2,4-diaryithiophenes via the reaction between substituted styrenes and sulfur. Besides the major product of 2,4-diarylthiophene, some minor 2,5-diarylthiophenes are also found in this reaction. Similarly, butadiynes can react with hydrogen sulfide to afford thiophenes. However, at 600°C in the presence of a ferrous sulfide-alumina catalyst, styrene reacted with hydrogen sulfide to give 60% benzothiophene." On the other hand, thiophenes can also be prepared via the reaction between ethylbenzene and sulfur, acetophene and hydrogen sulfide, or 1,4-diketones and phosphorus trisulfide (or phosphorus pentasulfide). The preparation of 2,4-diarylthiophene has been reviewed. ... [Pg.267]

Thiophenes are generally obtained by sulfuration of 1,4-dicarbonyl compounds (Paal s)mthesis). The preparation of the highly substituted 2-(4-bromophenyl)-5-(3,4-dimethoxyphenyl)-3,4-dimethylthiophene from the respective 1,4-diketone represents a recent example. This type of reaction can be performed as a solid-phase synthesis with polymer-bound diketones (132) and LR (eq 44). Trifluoroacetic acid releases the thiophene (133) from the solid support. Bismuth triflate in 1,3-dialkylimida-zolium fluoroborate has been utilized as a catalytic ionic liquid system for the synthesis of thiophenes from 1,4-diketones and LR with significantly improved yields. [Pg.63]


See other pages where Diketones, reaction with sulfur preparation is mentioned: [Pg.101]    [Pg.113]    [Pg.914]    [Pg.90]    [Pg.914]    [Pg.894]    [Pg.74]    [Pg.113]    [Pg.256]    [Pg.3188]    [Pg.341]    [Pg.489]    [Pg.884]    [Pg.937]    [Pg.54]    [Pg.258]    [Pg.884]    [Pg.149]    [Pg.1246]    [Pg.892]    [Pg.937]    [Pg.414]    [Pg.875]    [Pg.875]    [Pg.149]    [Pg.1246]    [Pg.3603]    [Pg.4700]    [Pg.57]    [Pg.875]   
See also in sourсe #XX -- [ Pg.647 ]




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1 3 Diketones preparation

1.3- Diketones reactions

Diketones, reaction with sulfur

Preparation reaction with

Preparation with

Reactions, with 3-diketones

Sulfur preparation

Sulfur reaction with

With 0-diketones

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