- Addition of hydrogen halides to alkylidenecyclopropanes: A highly efficient and stereoselective method for the preparation of homoallylic halides
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The reaction of alkylidenecyclopropanes with HCl or with HBr proceeds very smoothly at 120°C to produce the corresponding homoallylic halides stereoselectively in good to excellent yields. For example, the reaction of (1-phenylbenzylidene)cyclopropane, (1-butylpentylidene)cyclopropane and octylidenecyclopropane with hydrochloric acid produced the corresponding homoallylic chlorides, 4-chloro-1,1-diphenyl-1-butene, 4-butyl-1-chloro-3-octene and (E)-1-chloro-3-undecene in 99, 96, and 87% yields, respectively. The reaction of (1-butylpentylidene)cyclopropane with hydrobromic acid yielded 1-bromo-4-butyl-3-octene in 95% yield.
- Siriwardana, Amal I.,Nakamura, Itaru,Yamamoto, Yoshinori
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- Ring opening of methylenecyclopropanes with halides in liquid sulfur dioxide
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Methylenecyclopropanes (MCP) undergo ring opening reactions with group I and II metal halides and ammonium halides in liquid SO2 to afford homoallylic halides, which are versatile reagents in organic synthesis. The developed reaction conditions are compatible with acid-labile substrates such as N-Boc-protected compounds. Liquid SO2 is a polar reaction medium with Lewis acid properties that solubilizes inorganic salts. The unique properties of SO2 were demonstrated by control experiments: 1) upon performing the reactions with the aforementioned salts in conventional solvents, the MCP ring opening was not observed either in the presence of catalytic amounts of H3PO4 (similar pKa to that of H2SO3), or in the absence of H3PO4; 2) a solution of SO2 in THF exhibited similar properties to that of liquid SO2.
- Le?kovskis, Kristaps,Gulbe, Krista,Mishnev, Anatoly,Turks, Māris
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supporting information
(2020/10/19)
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- Ruthenium-catalyzed hydroarylation of methylenecyclopropanes through C-H bond cleavage: Scope and mechanism
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Intermolecular hydroarylation reactions of highly strained methylenecyclopropanes 2-phenylmethylenecyclopropane (1), 2,2- diphenylmethylenecyclopropane (2), methylenespiropentane (3), bicyclopropylidene (4), (dicyclopropylmethylene)cyclopropane (5), and benzhydrylidenecyclopropane (6) through C-H bond functionalization of 2-phenylpyridine (7 a) and other arenes with directing groups were studied. The reaction was very sensitive to the substitution on the methylenecyclopropanes. Although these transformations involved (cyclopropylcarbinyl)-metal intermediates, substrates 1 and 4 furnished anti-Markovnikov hydroarylation products with complete conservation of all cyclopropane rings in 11-93 % yield, whereas starting materials 3 and 5 were inert toward hydroarylation. Methylenecyclopropane 6 formed the products of formal hydroarylation reactions of the longest distal C-C bond in the methylenecyclopropane moiety in high yield, and hydrocarbon 2 afforded mixtures of hydroarylated products in low yields with a predominance of compounds that retained the cyclopropane unit. As byproducts, Diels-Alder cycloadducts and self-reorganization products were obtained in several cases from substrates 1-3 and 5. The structures of the most important new products have been unambiguously determined by X-ray diffraction analyses. On the basis of the results of hydroarylation experiments with isotopically labeled 7 a-[D5], a plausible mechanistic rationale and a catalytic cycle for these unusual ruthenium-catalyzed hydroarylation reactions have been proposed. Arene-tethered ruthenium-phosphane complex 53, either isolated from the reaction mixture or independently prepared, did not show any catalytic activity. Copyright
- Ackermann, Lutz,Kozhushkov, Sergei I.,Yufit, Dmitry S.
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supporting information
p. 12068 - 12077
(2012/10/29)
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- Studies on the mechanism, selectivity, and synthetic utility of lactone reduction using SmI2 and H2O
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Although simple aliphatic esters and lactones have long been thought to lie outside the reducing range of SmI2, activation of the lanthanide reagent by H2O allows some of these substrates to be manipulated in an unprecedented fashion. For example, the SmI2-H2O reducing system shows complete selectivity for the reduction of 6-membered lactones over other classes of lactones and esters. The kinetics of reduction has been studied using stopped-flow spectrophotometry. Experimental and computational studies suggest that the origin of the selectivity lies in the initial electron-transfer to the lactone carbonyl. The radical intermediates formed during lactone reduction with SmI2-H2O can be exploited in cyclizations to give cyclic ketone (or ketal) products with high diastereoselectivity. The cyclizations constitute the first examples of ester-alkene radical cyclizations in which the ester carbonyl acts as an acyl radical equivalent.
- Parmar, Dixit,Duffy, Lorna A.,Sadasivam, Dhandapani V.,Matsubara, Hiroshi,Bradley, Paul A.,Flowers II, Robert A.,Procter, David J.
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supporting information; experimental part
p. 15467 - 15473
(2010/02/16)
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- Lewis acid catalyzed reaction of methylenecyclopropanes with 1,2-diphenyldiselane or 1,2-di-p-tolyldisulfane
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(Chemical Equation Presented) Catalyzed by Lewis acid, 1,2-diphenyldiselane or 1,2-di-p-tolyldisulfane could add to methylenecyclopropanes smoothly. Compared with the reported free radical additions, the results were quite different. A four-membered carbon ring was constructed to give cyclobutane-1,1-diylbis(phenylselane) derivatives or cyclobutane-1,1-diylbis(p- tolylsulfane) derivatives as products, which are useful intermediates in organic synthesis.
- Yu, Lei,Meng, Jundong,Xia, Ling,Guo, Rong
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supporting information; experimental part
p. 5087 - 5089
(2009/10/17)
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- Ring-opening reaction of methylenecyclopropanes with LiCl, LiBr or NaI in acetic acid
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The methylenecyclopropanes 1 react with LiCl, LiBr or NaI at 80°C to give the corresponding gem-disubstituted homoallylic halides 2 in good to excellent yields in acetic acid. In some cases, the ring-opening reaction can be completed within 5 min to give
- Huang, Jin-Wen,Shi, Min
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p. 2057 - 2062
(2007/10/03)
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- Dihalogenation of gem-aryl-disubstituted methylenecyclopropanes by DEAD, DIAD/TiX4 or free halogen
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The reaction of gem-aryl-disubstituted methylenecyclopropanes with TiX 4/diethyl azodicarboxylate and TiX4/diisopropyl azodicarboxylate in 1,2-dichloroethane gave the dihalogenated ring-opened product, 2,4-dihalobut-1-ene, in moderate-to-excellent yields under mild conditions. On the basis of the proposed Orton-type mechanism, we found that this reaction can also be carried out with free halogens such as bromine or iodine to give the same products in good yields. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- Shao, Li-Xiong,Zhao, Lin-Jing,Shi, Min
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p. 4894 - 4900
(2007/10/03)
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- Amination of arenes through electron-deficient reaction cascades of aryl epoxyazides
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(Matrix presented) Aryl epoxyazides undergo efficient electron-deficient reaction cascades mediated by Lewis acids, leading to regiospecific amination of the aromatic ring.
- Lang, Stuart,Kennedy, Alan R.,Murphy, John A.,Payne, Andrew H.
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p. 3655 - 3658
(2007/10/03)
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- A convenient one-pot synthesis of homoallylic halides and 1,3-butadienes
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An efficient one-pot synthetic pathway for the preparation of homoallylic halides by in situ generated MgBrCl-promoted ring opening of cyclopropylcarbinyl acetates has been established. An easily accessible one-pot synthetic protocol of 1,3-butadienes by the elimination of hydrogen halides from the resulting homoallylic halides in the presence of an excess amount of strong base has also been developed.
- Wong, Ken-Tsung,Hung, Ying-Yueh
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p. 8033 - 8036
(2007/10/03)
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- Ring-opening reactions of methylenecyclopropanes promoted by metal halides
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(Matrix presented) The methylenecyclopropanes (MCPs) react with various metal chlorides or bromides to give the corresponding homoallylic chlorides or bromides in good yields.
- Xu, Bo,Shi, Min
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p. 1415 - 1418
(2007/10/03)
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- N6 -substituted adenosines for treating pain
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N6 -Substituted diarylalkyladenosines and pharmaceutically acceptable acid addition salts having highly desirable central nervous system and cardiovascular properties, processes for their manufacture and pharmaceutical compositions and methods for using said compounds and compositions are described.
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- SIMPLE PREPARATION OF ω-gem-DISUBSTITUTED HOMOALLYL CHLORIDES
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The synthesis of the title compounds, starting from γ-butyrolactone, is described.
- Biernacki, Wladyslaw,Gdula, Andrzej
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p. 849 - 852
(2007/10/02)
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