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1.
Dr. Christine Beemelmanns Dr. Dominik Nitsch Dr. Christoph Bentz Prof. Dr. Hans-Ulrich Reissig 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(37):8780-8789
A series of γ-indolylketones with fluorine, cyano or alkoxy substituents at the benzene moiety was prepared and subjected to samarium diiodide-promoted cyclization reactions. The desired dearomatizing ketyl cascade reaction forming two new rings proceeded in all cases with high diastereoselectivity, but with differing product distribution. In most cases, the desired annulated tetracyclic compounds were obtained in moderate to good yields, but as second product tetracyclic spirolactones were isolated in up to 29 % yield. The reaction rate was influenced by the substituents at the benzene moiety of the substrate as expected, with electron-accepting groups accelerating and electron-donating groups decelerating the cyclization process. In case of a difluoro-substituted γ-indolylketone a partial defluorination was observed. The intermediate samarium enolate of the tetracyclic products could be trapped by adding reactive alkylating agents as electrophiles delivering products with quarternary carbons. In the case of a dimethoxy-substituted tetracyclic cyclization product a subsequent reductive amination stereoselectively provided a pentacyclic compound that was subsequently N-protected and subjected to a regioselective elimination. The obtained functionalized pentacyclic product should be convertible into the alkaloid brucine by four well-established steps. Overall, the presented report shows that functionalized tetracyclic compounds with different substituents are rapidly available with the samarium diiodide cascade cyclization as crucial step. Hence, analogues of the landmark alkaloid strychnine, for example, with specific fluorine substitutions, should be easily accessible. 相似文献
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Synthesis of Polycyclic Tertiary Carbinamines by Samarium Diiodide Mediated Cyclizations of Indolyl Sulfinyl Imines 下载免费PDF全文
Dr. Chintada Nageswara Rao Prof. Dr. Dieter Lentz Prof. Dr. Hans‐Ulrich Reissig 《Angewandte Chemie (International ed. in English)》2015,54(9):2750-2753
Samarium diiodide mediated cyclizations of N‐acylated indole derivatives bearing sulfinyl imine moieties afforded polycyclic tertiary carbinamines with moderate to excellent diastereoselectivities. Lithium bromide and water turned out to be the best additives to achieve these transformations in good yields. Using enantiopure sulfinyl imines the outcome strongly depends on the reactivity of the indole moiety. Whereas with unactivated indole derivatives desulfinylation and formation of racemic products was observed, indoles bearing electron‐withdrawing substituents at C‐3 afforded the polycyclic products with intact N‐sulfinyl groups and with excellent diastereoselectivity, finally allowing the preparation of enantiopure tertiary carbinamines. The mechanisms of these processes are discussed. 相似文献
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Byung Woo Yoo Heung Soo Baek Sam Rok Keum Cheol Min Yoon Ghil Soo Nam Sung Hoon Kim 《合成通讯》2013,43(23):4317-4322
The reductive cleavage of thiobenzoates promoted by samarium diiodide afforded various kinds of disulfides in good yields under mild and neutral conditions. 相似文献
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Heung Soo Baek Byung Woo Yoo Sam Rok Keum Cheol Min Yoon Sung Hoon Kim Joong Hyup Kim 《合成通讯》2013,43(1):31-38
α-Haloketones reacted with acyl cyanides to form 1,3-diketones in the presence of samarium diiodide. The reaction was assumed to proceed via a mechanism involving samarium enolates formed in situ from α-haloketones. 相似文献
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SinceintroducedbyKaganandhisgroups',Sml,hasbeenextensivelyinvestigatedasamild,neutral,selectiveandversatilesingIeelectrontransferreductantinsyntheticchemistry=.Suchas,Barbierreactions,Reformatskyreactions,pinacolcouplingandketone-oIefinreductivehavebeenreportedusingSmI,asreagent.Thereactivitiesofvariousnitrogenfunctionalgroups(imine,oxime,nitro,azo,cyano)towardsSmI,havealsobeenexamined.Recently,ourgrouphasreportedtheintermolecularreductivecouplingofnitrogroupswithcyanogroupsinducedbySml='.… 相似文献
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The deoxygenation and reduction of several kinds of organic substrates with samarium diiodide (SmI2) in satisfactory yields are reported. 相似文献
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Cycloalkanones appended with an α, β-unsaturated carbonyl side chain react with 2.25 equivalents of samarium diiodide to form bicyclic or tricyclic bridgehead hydroxy compounds stereoselectively in moderate yield. 相似文献
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Parthasarathy Saravanan Suparna Gupta Arpita DattaGupta Sonia Gupta Vinod K. Singh 《合成通讯》2013,43(15):2695-2699
The cleavage of α-hydroxy tert-butyldimethylsilyl ether to diol takes place efficiently with LAH. It has been proposed that the reaction proceeds via intramolecular hydride transfer from the alkoxy aluminium hydride. In order to substantiate this, reduction of TBDMS ether with LAH in a variety of substrates was studied. 相似文献
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Theuseofsamariumdiiodideasastrongone-electrontransferreducingandcouplingreagentinorganicsynthesishasgainedincreasingpopularity,especiallyinthepasttenyears1OurpreviousworkonsomedeoxygenationandsomereductivecleavageofSe-SeorTe-TebondwithSmI2wasrepel'te... 相似文献
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Xiao Liang XU Wei Min ZHU Yong Min ZHANG 《中国化学快报》2005,16(12):1566-1568
1-(β-Hydroxyalkyl)-l,3,4-oxadiazole derivatives were synthesized via reductive addition reactions of 2-chloromethyl-l,3,4-oxadiazole with carbonyl compounds under mild conditions promoted by SmI2. 相似文献
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Samarium diiodide reductively cleaves the S-S bond of sodium alkyl thiosulfates to give the corresponding disulfides in moderate to good yields under mild and neutral conditions. 相似文献
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Acylthioarylthioacetals are cleaved selectively by tributyltin hydride/AIBN affording thioacyls radicals, which can react with tethered carbon-carbon double or triple bond to form functionalized cyclopentanes. 相似文献
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Samarium (II) iodide has been successfully utilized as a strong one-electron transfer reducing agent for the cyclodimerization of α, β-unsaturated ketones. The absence of any alcohol as proton source is essential. The reaction is regioselective over the competitive carbon-carbon double bond reduction and stereocontrolled. The configuration of the cyclodimerization products, has been confirmed by X-ray analysis. 相似文献
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Chimmanamada U. Dinesh Hans-Ulrich Reissig 《Angewandte Chemie (International ed. in English)》1999,38(6):789-791
Beware of samarium diiodide and aryl ketones! If the ketyl radical anion which is formed by electron transfer finds a properly placed aryl group, a highly diastereoselective cyclization may occur. After the transfer of a second electron and protonation bi- and polycyclic products with a common 1,4-cyclohexadiene moiety may be isolated [Eq. (a)]. X=CHCO2R, NCH2Ph; HMPA=(Me2N)3PO. 相似文献
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Diphenyl disulfide is reduced by samarium diiodide to yield samarium phenylthiolate. This new thiolate anion species mildly reacts with acyl chlorides to give thiolesters in good yields. 相似文献
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Allenic acids are found to add to dicyclohexylcarbodiimide affording, in the presence of Et2NH, the 4H-1,3-oxazin-4-ones 5 via 4 . Under neutral conditions, they add to diaryl- or pyridyl(cyclohexyl)carbodiimides and triphenylketene imine to give the corresponding tricyclo[5.2.2.01,5]undeca-4,8,10-trien-3-ones 7 , 8 , 9 , and 12 . The allenic phenyl ester 13a dimerises, on heating in a [2+2] head-to-head fashion, to 14 but fails to undergo intramolecular Diels-Alder cyclization, to 15 . 相似文献