- An effective synthesis of fused cyclic thiopyrans and pyrans by molybdenum(VI) sulfide catalyzed reduction of the corresponding thiopyranones and pyranones
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The synthesis of fused cyclic dihydrothiopyrans 2a-c from dihydrothiopyranones 1a-c and thiopyrans 2d-f from thiopyranones 1d-f by catalytic reduction over molybdenum(VI) sulfide (MoS3) has been studied. The hydrogenolysis of the carbonyl group of 1a-f over MoS3 catalyst proceeded selectively to give the corresponding 2a-f in high yields. Neither alcohols nor olefins were not detected in the products. The method was also applied successfully to the synthesis of dihydropyran 2h and pyran 2g from dihydropyranone 1h and pyranone 1g.
- Takido,Takagi,Itabashi
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- Cu-mediated: vs. Cu-free selective borylation of aryl alkyl sulfones
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A Cu-catalysed borylation of aryl alkyl sulfones was developed for the high yield synthesis of versatile arylboronic esters using a readily prepared NHC-Cu catalyst. In addition, the selective cleavage of either alkyl(C)-sulfonyl or aryl(C)-sulfonyl bonds
- Hu, Jiefeng,Huang, Mingming,Marder, Todd B.,Radius, Udo,Tang, Man,Westcott, Stephen A.
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p. 395 - 398
(2022/01/19)
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- Direct Access to S-Heterocycles by Scandium(III) Triflate Catalyzed Cyclization of Aromatic Thiols and Diols
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A simple and environmentally friendly method to prepare S-heterocycles by cyclization of aromatic thiols and diols with H2O as a byproduct is described. The Sc(OTf)3-catalyzed dehydrative cyclizations of aromatic thiols and diols provided the corresponding thiopyran and thiophene derivatives. Control experiments were also performed to obtain insights into the reaction pathway.
- Minakawa, Maki,Minami, Keisuke,Sato, Yuya
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supporting information
p. 1869 - 1873
(2021/07/31)
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- Investigating the microwave-accelerated Claisen rearrangement of allyl aryl ethers: Scope of the catalysts, solvents, temperatures, and substrates
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The microwave-accelerated Claisen rearrangement of allyl aryl ethers was investigated, in order to gain insight into the scope of the catalysts, solvents, temperatures, and substrates. Among the catalysts examined, phosphomolybdic acid (PMA) was found to greatly accelerate the reaction in NMP, at temperatures ranging from 220 to 300 °C. This method was found to be useful for preparing several intermediates previously reported in the literature using precious metal catalysts such as Au(I), Ag(I), and Pt(II). Additionally, substrates bearing bromo and nitro groups on the aryl portion required careful tailoring of the reaction conditions to avoid complex product profiles.
- Hui, Zi,Jiang, Songwei,Qi, Xiang,Ye, Xiang-Yang,Xie, Tian
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supporting information
(2020/05/18)
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- Nickel-Catalyzed Inter- and Intramolecular Aryl Thioether Metathesis by Reversible Arylation
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A nickel-catalyzed aryl thioether metathesis has been developed to access high-value thioethers. 1,2-Bis(dicyclohexylphosphino)ethane (dcype) is essential to promote this highly functional-group-tolerant reaction. Furthermore, synthetically challenging macrocycles could be obtained in good yield in an unusual example of ring-closing metathesis that does not involve alkene bonds. In-depth organometallic studies support a reversible Ni0/NiII pathway to product formation. Overall, this work not only provides a more sustainable alternative to previous catalytic systems based on Pd, but also presents new applications and mechanistic information that are highly relevant to the further development and application of unusual single-bond metathesis reactions.
- Delcaillau, Tristan,Bismuto, Alessandro,Lian, Zhong,Morandi, Bill
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supporting information
p. 2110 - 2114
(2019/12/24)
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- Mo-Based Oxidizers as Powerful Tools for the Synthesis of Thia- and Selenaheterocycles
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A highly efficient synthetic protocol for the synthesis of thia- and selenaheterocycles has been developed. By employing a MoCl5-mediated intramolecular dehydrogenative coupling reaction, a broad variety of structural motifs was isolated in yields up to 94 %. The electrophilic key transformation is tolerated by several labile moieties like halides and tertiary alkyl groups. Due to the use of disulfide or diselenide precursors, a high atom efficiency was achieved.
- Franzmann, Peter,Beil, Sebastian B.,Schollmeyer, Dieter,Waldvogel, Siegfried R.
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p. 1936 - 1940
(2019/01/14)
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- Chlorotrimethylsilane and Sodium Iodide: A Remarkable Metal-Free Association for the Desulfurization of Benzylic Dithioketals under Mild Conditions
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A novel metal-free process allowing the reductive desulfurization of various benzylic dithioketals to afford diarylmethane and benzylester derivatives with good to excellent yields is reported. At room temperature, this mild reduction process requires only the use of TMSCl and NaI in CH2Cl2 and tolerates a large variety of functional groups. (Figure presented.).
- Zhao, Guangkuan,Yuan, Ling-Zhi,Alami, Mouad,Provot, Olivier
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p. 2522 - 2536
(2018/05/14)
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- Efficient access to 1,4-benzothiazine: Palladium-catalyzed double C-S bond formation using Na2S2O3 as sulfurating reagent
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A novel Pd-catalyzed double C-S bond formation coupling reaction has been developed. This protocol, in which Na2S2O3 was used as sulfurating reagent in metal-catalyzed reactions, provides an efficient method for the synthe
- Qiao, Zongjun,Liu, Hui,Xiao, Xiao,Fu, Yana,Wei, Jianpeng,Li, Yuxue,Jiang, Xuefeng
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supporting information
p. 2594 - 2597
(2013/07/19)
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- Novel chiral, sulfur-containing heteroarotinoids with liquid crystal properties
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Synthetic methods were developed to prepare ethyl (E)-4-[2-(3,4-dihydro-2-n-octyl-1-oxy-2H-1-benzothio-pyran-6-yl)-1- propenyl]-benzoate (1) and ethyl ( E)-4-[2-(3,4-dihydro-2-n-octyl-2H-1-benzothiopyran-6-yl)-1-propenyl]benzoate (10). These are the first examples of heteroarotinoids which possess properties of liquid crystals. The properties were evaluated using differential scanning calorimetry and by use of polarizing micrography. Both displayed textures which are typical of a smectic or cholesteric phase.
- Weerasekare, G. Mahika,Berlin, K. Darrell,Sunkara, Haribabu,Ford, Warren T.
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p. 993 - 1006
(2007/10/03)
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- Biologically active heteroarotinoids exhibiting anticancer activity and decreased toxicity
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A series of retinoids, containing heteroatoms in a cyclic ring and called heteroarotinoids, were synthesized, and their biological activity was evaluated using tissue culture lines that have measurable responses to trans- retinoic acid (t-RA). Transglutam
- Benbrook, Doris M.,Madler, Matora M.,Spruce, Lyle W.,Birckbichler, Paul J.,Nelson, Eldon C.,Subramanian, Shankar,Mahika Weerasekare,Gale, Jonathan B.,Patterson Jr., Manford K.,Wang, Binghe,Wang, Wei,Lu, Shennan,Rowland, Tami C.,DiSivestro, Paul,Lindamood III, Charles,Hill, Donald L.,Berlin, K. Darrell
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p. 3567 - 3583
(2007/10/03)
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- Chloroperoxidase-catalyzed asymmetric synthesis of a series of aromatic cyclic sulfoxides
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The chloroperoxidase (CPO) catalyzed oxidation of a series of rigid aromatic sulfides of well-defined geometry has been studied by the use of enantioselective gas chromatography for the determination of product composition and sulfoxide enantiomeric excess. The almost planar 1-thiaindane was found to be an excellent substrate, giving a quantitative yield of the (-)-(R)-1-oxide in 99% e.e. The sterically more demanding next higher homolog with a six-membered heterocyclic ring, 1-thiatetrahydronaphthalene (1-thiochroman), also gave a sulfoxide in high e.e. (≥ 96%) but in a much lower yield, indicating a preserved stereorecognition ability but a lower turnover rate. A carbonyl group in the 4-position (1-thiochroman-4-one) had no further effect on the CPO-mediated sulfoxidation. Enantio-selectivity was lost for the symmetric disulfide, 1,3-benzodithiol, indicating an equal accessibility of the Fe=O complex towards both sulfur atoms and an active site centred above the heme-iron atom. In all cases with pronounced enantioselectivity the reaction gave the (R)-sulfoxide as observed previously with alkyl aryl sulfides. A change of oxygen source from hydrogen peroxide to t-butyl hydroperoxide and a longer reaction time gave a higher chemical but a lower optical yield, most likely due to an increased competition by the uncatalyzed oxidation reaction in this case.
- Allenmark, Stig G.,Andersson, Malin A.
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p. 1089 - 1094
(2007/10/03)
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- Antioxidant Activity of 1-Thio-α-tocopherol and Related Compounds. EPR, ENDOR, and UV-Visible Absorption Spectra of Some of the Derived Phenoxyl Radicals
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The inhibition of the azobis(isobutyronitrile) thermally autoxidation of styrene at 30 deg C by 1-thio-α-tocopherol and related 6-hydroxythiochromans has shown that these compounds trap fewer than 2.0 peroxyl radicals per molecule (between 1.0 and 1.8) and that they are only slightly less reactive toward peroxyl radicals than structurally related 6-hydroxychromans.A number of thiochromanoxyl radicals were generated photolytically, and their EPR and ENDOR spectra were recorded.The ENDOR cavity is unique in that it allows photolysis of the sample, and this represents the first report on the ENDOR spectra of transient radicals that must be continuously generated by photolysis.The hyperfine splittings for thiochromanoxyls are similar to those of chromanoxyls radical, but their g values are higher by 0.0008.The UV-visible absorption spectrum of the thiotocopheroxyl radical has a band maximum at 488 nm, well above the 413 nm of α-tocopheroxyl.An addendum reports that 5-hydroxy-2,4,6,7-tetramethylbenzofuran is only ca. 10percent as active toward peroxyl radicals at 30 deg C as structurally related 2,3-dihydro-5-hydroxybenzofurans, the latter being a class of phenols which we have previously shown to be the most active in trapping peroxyl radicals.5,6 An improved synthesis of 1-thio-α-tocopherol and a correction to earlier reports regarding purported syntheses of this compound are also included.
- Zahalka, H. A.,Robillard, B.,Hughes, L.,Lusztyk, J.,Burton, G. W.
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p. 3739 - 3745
(2007/10/02)
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- MODERN FRIEDEL-CRAFTS CHEMISTRY. XI. CYCLIZATION OF ARYL HALOALKYL SULFONES, ARYLSULFONYLACYL CHLORIDES AND THEIR CORRESPONDING SULFIDES
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The sulfone group deactivation for cyclialkylation and cycliacylation reactions in the presence of Friedel-Crafts catalysts was demonstrated in a number of aryl chloroalkylsulfones (1-8) and arylsulfonylacyl chlorides (17a-22a), respectively.As expected, the corresponding arylchloroalkyl sulfides (9-16) and arylmercaptoacyl chlorides (13a-28a) underwent ring-closure reaction in most cases under the same conditions.The ease of cyclization was governed by the ring size, the stability of the attacking carbocation and the nucleophilicity of the aryl moiety.Also, the behaviour of benzyl sulfones (29, 31a, and 32a) and sulfides (33, 34a and 36a) was inconsistent.Noteworthy, the Friedel-Crafts cyclization reaction is thus considered an accessible method for the synthesis of compounds 37-41 and 45, 51.
- Abdel-Wahab, Aboel-Magd A.,El-Khawaga, Ahmed M.,El-Zohry, Maher F.,Khalaf, Ali A.
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- One-Electron Chemical Reductions of Phenylalkylsulfonium Salts
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Twenty-two arylalkylsulfonium salts have been reduced with potassium in graphite in tetrahydrofuran and the sulfide products identified.Two trialkylsulfonium salts did not reduce under these conditions.Comparison of the sulfides from a series of monophenylalkylsulfonium salts reveals a leaving-group propensity of benzyl > secondary > primary > methyl > phenyl in a ratio of 28:(6.0 +/- 0.3):1.0:(0.53 +/- 0.09): 0.05.The cleavage ratio is shown to be independent of the electron source and the homogeneity of heterogeneity of the reaction in two cases.Multiplicative transitivity of the above ratios is not observed, although the same qualitative order is found for other comparisons.These results are interpreted in terms of the initial formation of a ?-ligand radical anion sulfonium cation, which undergoes cleavage to a carbon radical and a sulfide.This appears to be the first evidence for this type of structure in a sulfur system.Leaving-group propensities different from the above order are observed in reductions of diphenylsulfonium and benzo-fused sulfonium salts, and rationales are offered.The intermediates in these reactions appear to be different from those involved in radical additions to, or displacements on, sulfur.
- Beak, Peter,Sullivan, Thomas A.
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p. 4450 - 4457
(2007/10/02)
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