- Fully substituted pyranones via quasi-heterogeneous genuinely ligand-free migita-stille coupling of iodoacrylates
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Migita-Stille coupling of (Z)-?2-iodoacrylates with (E)-?±-stannyl allylic alcohols to furnish 5-alkylidene-4-substituted-5,6-dihydro-2H-pyran-2-ones is efficiently catalyzed by 2% Pd black in DMF, while Pd(PPh3)4 is inactive. Heterogeneous Pd released in solution is most likely responsible for the catalysis. The reaction is applicable to other substrates, without having to resort to ligands, additives, and/or solid support for Pd. The resulting pyranones can be rearranged to fully functionalized pyranones in another single step.
- Kratochv??l, Ji????,Nov??k, Zden??k,Ghavre, Mukund,Nov??kov??, Lucie,R????i??ka, Ale??,Kune??, Ji????,Pour, Milan
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p. 520 - 523
(2015/03/04)
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- Silver-catalyzed direct addition of terminal alkynes to simple cyclic ketones in water
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The first catalytic addition of terminal alkynes to simple cyclic ketones in water catalyzed by silver was developed. Cyclic ketones were reacted with terminal alkynes efficiently in water to give the corresponding propargyl alcohols. Georg Thieme Verlag
- Jia, Zhenhua,Li, Xingshu,Chan, Alberts. C.,Li, Chao-Jun
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p. 2758 - 2762
(2013/02/21)
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- Synthesis of cyclic N-tosyliminocarbonates by Lewis acid catalyzed allylic substitution of trichloroacetimidates
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Allylic trichloroacetimidates bearing a δ-N-tosylcarbamoyloxy group were prepared in two steps from the corresponding diols, and their Bronsted and Lewis acid catalyzed cyclization reactions were investigated. It was found that N-tosylcarbamates derived from secondary and tertiary alcohols bearing alkyl substituents undergo a chemoselective allylic alkylation to give N-tosyliminocarbonates in good isolated yields. In turn, aryl-substituted substrates tend to give oxazolines by abstraction of the carbamate functionality. The cyclization of N-tosylcarbamates derived from secondary alcohols preferentially give trans-iminocarbonates. However, the trans selectivity varied and depended on the substitution pattern, configuration of the substrate, and the catalyst. A high trans selectivity could be achieved from (E) substrates by using TMSOTf as the catalyst. The synthetic utility of iminocarbonates was demonstrated by transforming them into 1,2-diols and cyclic carbonates as well as into N-tosyloxazolidinones by a halide ion-induced rearrangement. Copyright
- Grigorjeva, Liene,Jirgensons, Aigars
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supporting information
p. 5307 - 5316
(2012/10/30)
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- Facile synthesis of dihaloheterocycles via electrophilic iodocyclization
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An efficient and facile electrophilic iodocyclization for the synthesis of various O-, N-, and S-containing dihaloheterocycles has been developed. A wide range of the substituted propargyl alcohols having -OH, -NTs, and -SAc functional groups reacted with molecular iodine or bromoiodine at ambient temperature to produce the corresponding dihalogenated O-, N-, and S-containing five- and six-membered heterocycles in good to high yields; Under optimized solvent conditions, the reactions of various substituted but-2-yn-1-ones bearing -OH, -NTs, and -SAc functional groups at C4-position, with iodine or bromoiodine at ambient temperature afforded the corresponding 3,4-diiodo- and 3-bromo-4-iodo-substituted furans, pyrroles, and thiophenes in good to high yields. Further transformation of the resulting iodine- or bromine-containing products to polyaromatics potentially of useful as organo-material intermediates has been investigated.
- Yang, Fan,Jin, Tienan,Bao, Ming,Yamamoto, Yoshinori
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supporting information; scheme or table
p. 10147 - 10155
(2012/01/03)
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- Synthesis of five- and six-membered dihalogenated heterocyclic compounds by electrophile-triggered cyclization
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Highly substituted dihalogenated dihydrofurans, dihydropyrroles, and dihydro-2H-pyrans bearing alkyl, vinyl, aryl, and heteroaryl moieties can be prepared in good to excellent yields (up to 99%) by allowing 1,4-butyne-diol, 4-aminobut-2-yn-1-ol, and pent-2-yne-1,5-diol derivatives to react with different electrophiles (I2, IBr, and ICl) at room temperature. Both halogen atoms generated from electrophiles were used effectively. The resulting halides can be further exploited by using palladium-catalyzed coupling reactions. The presence of trace amount of water is essential for this electrophilic cyclization.
- Ji, Ke-Gong,Zhu, Hai-Tao,Yang, Fang,Shaukat, Ali,Xia, Xiao-Feng,Yang, Yan-Fang,Liu, Xue-Yuan,Liang, Yong-Min
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supporting information; experimental part
p. 5670 - 5678
(2010/11/05)
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- Au(I)-catalyzed tandem [3,3]-sigmatropic rearrangement-cycloisomerization cascade as a route to spirocyclic furans
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Gold-catalyzed reaction of 1-(3-hydroxypropynyl)cycloalkanol derivatives was studied. The reaction profile was highly dependent on the ring size, migrating group, as well as reaction conditions. An efficient route to spirocyclic furans via tandem [3,3]-si
- Yeom, Hyun-Suk,Yoon, Suk-Jae,Shin, Seunghoon
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p. 4817 - 4820
(2008/02/05)
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- Gold-catalyzed intramolecular [3 + 2]-cycloaddition of arenyne-yne functionalities
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We report a new efficient intramolecular [3 + 2]-cycloaddition of unactivated arenyne (or enyne)-yne functionalities, catalyzed mainly by the AuPPh3SbF6 complex (2 mol %) under ambient conditions. The value of this cyclization is ref
- Lian, Jian-Jou,Chen, Po-Chiang,Lin, Yau-Ping,Ting, Hao-Chun,Liu, Rai-Shung
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p. 11372 - 11373
(2007/10/03)
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- Preparation, structure, and unique thermal [2 + 2], [4 + 2], and [3 + 2] cycloaddition reactions of 4-vinylideneoxazolidin-2-one
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The terminal allene Cα=Cβ bonds of 4-vinylidene-2-oxazolidinone (2) readily undergo [2 + 2] cycloaddition with a wide variety of terminal alkynes, alkenes, and 1,3-dienes irrespective of their electronic nature under strictly thermal activation conditions (70-100°C) and provide 3-substituted (Z)-methylenecyclobutenes 6, 3-substituted methylenecyclobutanes 7 and 8, and 3-vinylmethylenecyclobutanes 9, respectively, in good to excellent yields. Alkenes react with 2 with complete retention of configuration. The [2 + 2] cycloaddition is concluded to proceed via a concerted [(π2s + π2s)allene + π2s] Hueckel transition state on the basis of experimental evidences and quantum mechanical methods. Some highly polarized enones and nitrile oxide, on the other hand, react with 2 selectively at the internal C4=Cα double bonds and give spiro compounds 10 and 11, respectively. The bent allene bonds (173-176°) and the unique reactivity associated with 2 are attributed to a low-lying LUMO (Cα=Cβ) that is substantiated by a through-space σ*(N-SO2)-π*(Cα= Cβ) orbital interaction.
- Horino, Yoshikazu,Kimura, Masanari,Tanaka, Shuji,Okajima, Toshiya,Tamaru, Yoshinao
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p. 2419 - 2438
(2007/10/03)
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- Regiocontrolled Formation of 4,5-Dihydro-3(2H)-furanones from 2-Butyne-1,4-diol Derivatives. Synthesis of Bullatenone and Geiparvarin
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Two new methods for selective hydration of 1,1,4-trisubstituted 2-butyne-1,4-diols (1) to give 4,5-dihydro-3(2H)-furanone derivatives are reported.The first involves selective monoacetylation of the less hindered hydroxyl group of 1 followed by Ag(I)-cata
- Saimoto, Hiroyuki,Hiyama, Tamejiro,Nozaki, Hitosi
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p. 3078 - 3087
(2007/10/02)
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