- One-Pot Synthesis of Metastable 2,5-Dihydrooxepines through Retro-Claisen Rearrangements: Method and Applications
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A one-pot methodology to synthesize metastable bicyclic 2,5-dihydrooxepines from cyclic 1,3-diketones and 1,4-dibromo-2-butenes through the retro-Claisen rearrangement of syn-2-vinylcyclopropyl diketone intermediates is reported. DFT calculations were performed to understand the reaction selectivity and mechanisms towards [1,3]- or [3,3]-sigmatropic rearrangements, highlighting the crucial influence of the temperature. The reaction was successfully applied to a short protecting group-free total synthesis of radulanin A, a natural 2,5-dihydrobenzoxepine. Moreover, the strong herbicidal potential of this natural product is demonstrated for the first time.
- Zhang, Wei,Baudouin, Emmanuel,Cordier, Marie,Frison, Gilles,Nay, Bastien
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supporting information
p. 8643 - 8648
(2019/07/16)
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- Total synthesis of celastrol, development of a platform to access celastroid natural products
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Celastroid natural products, triterpenes, have been and continue to be investigated in clinical trials. Celastrol, and for that matter any member of the celastroid family, was prepared for the first time through chemical synthesis starting from 2,3-dimethylbutadiene. A triene cyclization precursor generated in 12 steps underwent a nonbiomimetic polyene cyclization mediated by ferric chloride to generate the generic celastroid pentacyclic core. In the cyclization, engagement of a tetrasubstituted olefin formed adjacent all carbon quaternary centers stereospecifically. With access to the carbocyclic core of the family of natural products, wilforic acid and wilforol A were prepared en route to racemic celastrol.
- Camelio, Andrew M.,Johnson, Trevor C.,Siegel, Dionicio
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supporting information
p. 11864 - 11867
(2015/10/06)
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- Reaktive Arsen-Heterocyclen. III. 3-Arsolene: Synthese und Reaktionen am Arsen
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3-Arsolenes (R=Ph, Me, t-Bu, Cl, R'=H, Me) are readily obtained from zirconocene-butadiene complexes and RAsCl2.Alkylation with methyl iodide gives arsonium salts (R=Ph, Me, t-Bu, R'=H, Me), treatment with sulphur gives sulphides (R=Me, t-Bu), while oxidation with Br2 or SO2Cl2 results in ring cleavage.From chloroarsolene substitution products (R=I, H, SPh, OMe, NMe2) as well as coupling products with As-As, As-O-As, and As-S-As units were synthesized.In addition, a number of arsolene complexes with the metals chromium, molybdenum, tungsten, and ruthenium is described. Key words: Arsolene; Zirconocene; Group 6; Ruthenium; Phosphorus
- Schenk, Wolfdieter A.,Voss, Eckhard
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- The Reaction of 1,2:3,4-Diepoxy-2,3-dimethylbutane with Nucleophiles
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To find out whether the 1,4-addition to 1,2:3,4-diepoxides, which so far has been observed only once, is of a more general character, we investigated the reaction of a variety of O-, C-, N-, and S-nucleophiles with the model compound 1,2:3,4-diepoxy-2,3-dimethylbutane (Scheme 4).In several cases, 1,4-addition products could, indeed, be observed besides the expected 1,2-adducts (Table).
- Farkas, Frederic,Wellauer, Thomas,Esser, Thomas,Sequin, Urs
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p. 1511 - 1519
(2007/10/02)
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- SYNTHESIS OF (Z)- AND (E)-3,4-DIMETHYL-HEX-3-ENE-1,6-DIOLS
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(Z)- and (E)-3,4-dimethyl-hex-3-ene-1,6-diols (1 and 2) have been synthesized in 23percent and 68percent yields by a three step sequence requiring only one purification at the end.The steps are a) coupling of 2-lithio-1,3-dithiane with (Z)- or (E)-1,4-dibromo-2,3-dimethylbut-2-ene (3 or 4), b) hydrolysis of the thioketals (8 and 9) with methyl iodide in a mixture of acetonitrile, acetone and water to give the 3,4-dimethyl-hex-3-ene-1,6-diols (10 and 11) and c) reduction with diisobutylaluminum hydride to provide the (Z)- and (E)-diols.
- Roberge, J. Y.,Deslongchamps, P.
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p. 817 - 828
(2007/10/02)
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- Ozonolysis of Some Tetrasubstituted Ethylenes
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The olefins 1,4-dibromo-2,3-dimethyl-2-butene, 1-bromo-2,3-dimethyl-2-butene, and 2,3-dimethyl-2-butene were ozonized under a variety of conditions.Ozonolysis of 1,4-dibromo-2,3-dimethyl-2-butene in acetone solvent leads to the unexpected products acetone diperoxide and triperoxide.The results are discussed with respect to questions of concertedness in ozonide formation, the need for activating groups in ozonide formation, and the possible intermediacy of dioxiranes.
- Murray, Robert W.,Agarwal, Sudhir K.
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p. 4698 - 4702
(2007/10/02)
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