- Selective Synthesis of Silacycles by Borane-Catalyzed Domino Hydrosilylation of Proximal Unsaturated Bonds: Tunable Approach to 1,n-Diols
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The tris(pentafluorophenyl)boron-catalyzed domino hydrosilylation of substrates carrying unsaturated functionalities in a proximal arrangement is presented to produce silacycles. Excellent levels of efficiency and selectivity were achieved in the cyclization by the deliberate choice of the hydrosilane reagents. The key to successful cyclic hydrosilylation is the reactivity enhancement of the second intramolecular hydrosilylation by a proximity effect. Not only dienes but also enones, enynes, ynones and enimines readily afford medium-sized silacycles under convenient and mild conditions. The cyclization proceeds with acceptable diastereoselectivity mainly controlled by the conformational bias towards inducing additional stereogenic centers. The silacycles obtained from this reaction were converted to 1,n-diols or 1,n-amino alcohols upon oxidation, thus rendering the present cyclization a powerful tool for accessing synthetically valuable building blocks. (Figure presented.).
- Shin, Kwangmin,Joung, Seewon,Kim, Youyoung,Chang, Sukbok
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- Lewis Base-Promoted Ring-Opening 1,3-Dioxygenation of Unactivated Cyclopropanes Using a Hypervalent Iodine Reagent
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A facile and effective system has been developed for the regio- and chemoselective ring-opening/electrophilic functionalization of cyclopropanes through C?C bond activation by [bis(trifluoroacetoxy)iodo]benzene with the aid of the Lewis basic promoter p-toluenesulfonamide. The p-toluenesulfonamide-promoted system works well for a wide range of cyclopropanes, resulting in the formation of 1,3-diol products in good yields and regioselectivity.
- Gieuw, Matthew H.,Ke, Zhihai,Yeung, Ying-Yeung
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supporting information
p. 3782 - 3786
(2018/03/13)
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- NOVEL RUTHENIUM COMPLEX AND METHOD FOR PREPARING METHANOL AND DIOL
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Provided is a method for preparing methanol and diol from cyclic carbonate, comprising: under a hydrogen atmosphere, in an organic solvent, and with the presence of a ruthenium complex (Ru(L)XYY') and an alkali, conducting a hydrogenation reduction reaction on the cyclic carbonate or polycarbonate to obtaib methanol and diol. Also provided is a ruthenium complex prepared from ruthenium and a tridentate amido diphosphine ligand. Also provided is a deuterated methanol and deuterated diol preparation method by substituting the hydrogen and ruthenium complex with deuterium.
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Paragraph 0091
(2015/09/23)
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- Triphosgene-pyridine mediated stereoselective chlorination of acyclic aliphatic 1,3-diols
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We describe a strategy to chlorinate stereocomplementary acyclic aliphatic 1,3-diols using a mixture of triphosgene and pyridine. While 1,3-anti diols readily led to 1,3-anti dichlorides, 1,3-syn diols must be converted to 1,3-syn diol monosilylethers to access the corresponding 1,3-syn dichlorides. These dichlorination protocols were operationally simple, very mild, and readily tolerated by advanced synthetic intermediates.
- Villalpando, Andrés,Saputra, Mirza A.,Tugwell, Thomas H.,Kartika, Rendy
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supporting information
p. 15075 - 15078
(2015/10/12)
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- Hydroxy-directed, fluoride-catalyzed epoxide hydrosilylation for the synthesis of 1,4-diols
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Abstract A novel highly regioselective, fluoride-catalyzed hydrosilylation of β-hydroxy epoxides has been developed. The reaction is modular and applicable to the synthesis of a broad range of 1,4-diols. Fluoride is crucial for two reasons: First, it promotes the formation of a silyl ether (which contains a Si-H bond) and, second, it enables ring opening by an intramolecular SN2 reaction through activation of the silane. The reaction can be performed under air. A modular, convergent, and stereoselective synthesis of 1,4-diols by epoxide hydrosilylation has been developed (see scheme). The reaction occurs under fluoride catalysis, is high yielding, highly regioselective, and can be carried out on a large scale.
- Zhang, Yong-Qiang,Funken, Nico,Winterscheid, Peter,Gans?uer, Andreas
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supporting information
p. 6931 - 6934
(2015/06/08)
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- Lewis acid-promoted electron transfer deoxygenation of epoxides, sulfoxides, and amine N-oxides: the role of low-valent niobium complexes from NbCl5 and Zn
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A mild and operationally simple deoxygenation of epoxides, sulfoxides, and amine N-oxides is described using a sub-stoichiometric amount of low-valent niobium complexes generated in situ from commercially available NbCl5 and zinc dust. The deoxygenation proceeds by a reductive cleavage of polarized O-C/O-N/O-S bonds through a single electron transfer from zinc metal to the niobium-substrate complex due to the high oxophilic nature of the niobium species. The presence of adjacent radical-stabilizing groups is beneficial to epoxide substrates; however the similar prerequisite does not apply to sulfoxides and amine N-oxides, where a broad range of substrates are efficiently deoxygenated in excellent yields.
- Oh, Kyungsoo,Knabe, William Eric
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experimental part
p. 2966 - 2974
(2009/05/30)
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- An oxidative entry into the amido trioxadecalin ring system.
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The amido trioxadecalin ring system is a key structural component of the architecturally interesting anticancer and immunosuppressive agents of the mycalamide, theopederin, and onnamide families of natural products. We report a new entry into this structure in which a mixed acetal serves as a surrogate for a formaldehyde hemiacetal in an addition to an oxidatively generated acyliminium ion. The stereochemical outcome of this process can be explained by the conformational preferences of the product ring system. [reaction: see text]
- Rech, Jason C,Floreancig, Paul E
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p. 1495 - 1498
(2007/10/03)
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- Regioselective nucleophilic ring opening of epoxides and aziridines derived from homoallylic alcohols
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The regioselectivity of nuclcopbilic ring opening of some 3,4-epoxy and 3,4-aziridino alcohols has been studied. The nucleophiles chosen were complex hydrides (LiAlH4, Red-Al and DIBAL) and Lipshutz- or Gilman-type organocuprate reagents. The C-4 substituent in the substrates was varied in order to study steric and electronic effects on the ring opening reactions. For alkyl substituents at C-4, most of the results can be explained on the basis of intramolecular delivery of the nucleophile to C-3 via a six-membered transition state, leading to 1,4-diols or 1,4-amine alcohol derivatives. In general, the epoxy alcohols gave poorer regioselectivity than the N-tosyl aziridino alcohols, for which selectivities of >95:5 were routinely obtained. The activating effect of a phenyl group at C-4 led to a switch in regiochemistry, with the 1,3-diol or 1,3-amino alcohol derivative as the major product.
- Tanner, David,Groth, Thomas
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p. 16139 - 16146
(2007/10/03)
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- 3-(N-methyl-N-alkyl)-amino 2-methoxymethylene propan 1-ol derivatives, a preparation process of the same and therapeutical compositions containing them
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The invention relates to 3-(N-methyl-N-alkyl)-amino 2-methoxymethylene propan 1-ol derivatives of the formula STR1 wherein R stands for an alkyl chain, A stands for: STR2 and Y represents various quaternary ammonia, to a preparation process of said compou
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- Highly Selective Amination of 1-Primary, 3-Secondary 1,3-Alkanediols. A New Approach to 3-Aminoalkyl 4-Nitrobenzoates
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1-Primary, 3-secondary 1,3-alkanediols can be selectively aminated at C-1 via OH/NH2 exchange by reaction with diethyl N-Boc-phosphoramidate in ether using triphenylphosphine/diethyl diazenedicaboxylate as condensing agent, and treatment of the resultant diethyl N-Boc-N-(3-hydroxyalkyl)phosphoramidates with 4-nitrobenzoyl chloride/pyridine, followed by dephosphorylation with hydrogen chloride in ethyl acetate.The reaction sequence affords the hydrochlorides of 3-aminoalkyl 4-nitrobenzoates in good yields.
- Gajda, Tadeusz
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p. 1108 - 1110
(2007/10/02)
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- REGIOSELECTIVE REDUCTIONS OF 2,3-EPOXY ALCOHOLS
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Regioselective reduction of 3-substituted-2,3-epoxy alcohols to 1,3-diols with sodium bis(2-methoxyethoxy)aluminum hydride (Red-al) is shown to be a general reaction for these substrates.
- Viti, Steven M.
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p. 4541 - 4544
(2007/10/02)
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- Synthesis of Saccharides and Related Polyhydroxylated Natural Products. 2. Simple Deoxyalditols
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Asymmetric epoxidation of allylic alcohols followed by selective hydride reduction provides a new route to chiral 1,3-diols and 1,3,5-triols; one of the 1,3,5-triols (21) is also synthesized from D-glucose.
- Ma, P.,Martin, V. S.,Masamune, S.,Sharpless, K. B.,Viti, S. M.
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p. 1378 - 1380
(2007/10/02)
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