- Tropylium salts as efficient organic Lewis acid catalysts for acetalization and transacetalization reactions in batch and flow
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Acetalization reactions play significant roles in the synthetically important masking chemistry of carbonyl compounds. Herein we demonstrate for the first time that tropylium salts can act as organic Lewis acid catalysts to facilitate acetalization and transacetalization reactions of a wide range of aldehyde substrates. This metal-free method works efficiently in both batch and flow conditions, prompting further future applications of tropylium organocatalysts in green synthesis.
- Lyons,Crocker,Enders,Nguyen
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supporting information
p. 3993 - 3996
(2017/09/08)
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- Acid-catalyzed highly diastereoselective and effective synthesis of 1,3-disubstituted tetrahydropyrano[3,4-b]indoles
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We successfully explored for the first time that trifluoroacetic acid (TFA) can effectively catalyze the oxa-Pictet-Spengler reaction of secondary tryptophols and acetals to synthesize 1,3-disubstituted 1,3,4,9-tetrahydropyrano[3,4-b]indoles in high yield (up to >99%) and diastereoselectivity (>20:1). The secondary tryptophols were synthesized from indole-3-acetic acid. The one-pot synthesis of tetrahydropyrano[3,4-b]indoles was successfully developed from secondary tryptophols and in situ prepared acetals from aldehydes and trimethylorthoformate and thus the cost-efficiency of the protocol was effectively enhanced. Finally, the catalytic asymmetric synthesis of the 1,3-disubstituted tetrahydropyrano[3,4-b]indole was also demonstrated after enantioselective achievement of highly enantiopure secondary tryptophols.
- Wang, Pei,Zhao, Jia-Zhen,Li, Hong-Feng,Liang, Xiang-Ming,Zhang, Ya-Lun,Da, Chao-Shan
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supporting information
p. 129 - 133
(2016/12/23)
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- Diterpenoid alkaloid lappaconine derivative catalyzed asymmetric α-hydroxylation of β-dicarbonyl compounds with hydrogen peroxide
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A new framework derived from the commercially available diterpenoid alkaloid lappaconitine was evaluated as a Bronsted base catalyst for the enantioselective α-hydroxylation of β-dicarbonyl compounds by using 30% hydrogen peroxide as a green and highly practical source of oxygen. This protocol allows convenient access to the corresponding α-hydroxy-β- oxo esters, α-hydroxy-β-oxo amides and (-)-kjellmanianone with up to 98% yield and 92% ee. Copyright
- Li, Zhi,Lian, Mingming,Yang, Fan,Meng, Qingwei,Gao, Zhanxian
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supporting information
p. 3491 - 3495
(2014/06/09)
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- Transformations of several monoterpenoids in the presence of aldehydes in supercritical solvents
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The reactivity of verbenol epoxide and isopulegol in supercritical solvents in the presence of aromatic aldehydes was studied using a flow type reactor and a heterogeneous catalyst (Al2O3) or no catalyst. The intramolecular transformations or interactions of reagents with the solvent prevailed in all cases; the yield of the products of intermolecular reactions of terpenoids with aldehydes was up to 1%. The aldehydes did not interact with verbenol epoxide but produced a considerable effect on the distribution of its isomerization products.
- Anikeev,Sivcev,Il'Ina,Korchagina,Statsenko,Volcho,Salakhutdinov
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p. 382 - 387
(2013/07/26)
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- New two-step sequence involving a hetero-Diels-Alder and a nonphenolic oxidative coupling reaction: A convergent access to analogs of steganacin
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A new family of analogs of steganacin, an important antimitotic compound, was accessed. It takes advantage of a completely stereoselective sequence of two key steps. The central dihydropyrane core is built by a highly diastereoselective and facially controlled hetero-Diels-Alder reaction. It is followed by a nonphenolic biaryl oxidative coupling with a complete atropo-stereoselectivity. It leads to a quick way to form cyclic biaryl lignans.
- Laurent, Mathieu Y.,Stocker, Vivien,Temgoua, Valéry Momo,Dujardin, Gilles,Dhal, Robert
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supporting information; experimental part
p. 1608 - 1611
(2011/04/26)
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- SUBSTITUTED ISOQUINOLINES AND THEIR USE AS TUBULIN POLYMERIZATION INHIBITORS
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The present invention relates generally to substituted isoquinolines and their use as tubulin polymerization inhibitors. In particular, the invention relates to substituted isoquinolines which possess useful therapeutic activity, use of these compounds in methods of therapy and the manufacture of medicaments as well as compositions containing these compounds
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Page/Page column 183-184
(2011/12/14)
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- Dichotomous reactivity in the reaction of triethyl- and triphenylphosphane HBr salts with dimethyl acetals: A novel entry to α-alkoxy-functionalized ylides and general synthesis of vinyl ethers and alkoxy dienes
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The discovery of dichotomous reactivity in the reaction of trialkyl- vs. triphenylphosphane HBr salts with acetals allows entry to functionalized α-methoxy phosphonium salts and a novel process for tertiary phosphane methylation. The new protocol opens a general entry to the synthesis of vinyl ethers and differentially substituted 1,3-dienes via Wittig reactions of the functionalized ylides derived from the α-methoxy phosphonium salts.
- Das, Priyabrata,McNulty, James
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supporting information; experimental part
p. 3587 - 3591
(2010/09/05)
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- A solvent-controlled highly efficient Pd-C catalyzed hydrogenolysis of benzaldehydes to methylbenzenes via a novel 'acetal pathway'
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Pd-C catalyzed hydrogenolysis of benzaldehydes to methylbenzenes has been described to proceed via a 'benzenemethanol pathway'. In this article, a novel 'acetal pathway' was first revealed by a systematic study when lower alcohols were used as solvents and a solvent-controlled highly efficient procedure was established.
- Xing, Lixin,Wang, Xinyan,Cheng, Chuanjie,Zhu, Rui,Liu, Bo,Hu, Yuefei
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p. 9382 - 9386
(2008/02/10)
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- Cobalt(II)-catalyzed chemoselective synthesis of acetals from aldehydes
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The acetalization of aldehydes has been studied with methanol, ethanol, and 2-propanol using CoCl2 in high yields under reflux conditions. The reaction is simple, efficient, chemoselective and does not involve any other additive.
- Velusamy, Subbarayan,Punniyamurthy
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p. 4917 - 4920
(2007/10/03)
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- Structure-activity relationship for DNA topoisomerase II-induced DNA cleavage by azatoxin analogues
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Eighteen analogues of the nonintercalative DNA topoisomerase II (topo II)-active epipodophyllotoxin-ellipticine hybrid, azatoxin, were synthesized and evaluated for their ability to induce topo II-mediated DNA strand breaks in vitro. In general, the SAR p
- Madalengoitia, Jose S.,Tepe, Jetze J.,Werbovetz, Karl A.,Lehnert, Erich K.,Macdonald, Timothy L.
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p. 1807 - 1815
(2007/10/03)
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- High Yield Endoselective Heterocycloadditions involving Benzylidenepyruvic Esters as the Heterodiene and an Alkoxystyrene as the Dienophile
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The benzylidenepyruvic esters 6, 10a-d and 11 smoothly reacted with the alkoxystyrenes 12 and 13 in refluxing hexane or toluene and in the presence of catalytic amounts of Eu(fod)3, thus selectively leading to the endo adducts 14-21 in high yields.This represents the first examples of an efficient heterocycloaddition of styrene derivatives without using the high pressure technique.The above adducts are potential intermediates for sugiresinol 7 and related tetrahydropyran neolignans.
- Dujardin, Gilles,Maudet, Mickael,Brown, Eric
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p. 8619 - 8622
(2007/10/02)
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- Antipsoriatic Anthrones with Modulated Redox Properties. 1. Novel 10-Substituted 1,8-Dihydroxy-9(10H)-anthracenones as Inhibitors of 5-Lipoxygenase
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The syntheses, the biological evaluation, and the structure-activity relationships of a novel series of 1,8-dihydroxy-9(10H)-anthracenones bearing acyl-, alkyl-, or alkylidene-linked aromatic substituents in the 10-position are described.The phenylacyl and phenylalkylidene analogs were far more potent inhibitors of 5-lipoxygenase (5-LO) from bovine polymorphonuclear leukocytes (IC50 values in the 10-7 M range) than the antipsoriatic drug anthralin, whereas phenylalkyl analogs were only weak inhibitors.Among the active compounds were both potent generators of hydroxyl radicals, as determined by deoxyribose degradation, and strong reducers of the stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH).However, several derivatives of this series maintained 5-LO inhibitory activity but did not generate hydroxyl radicals and were not reactive with DPPH.In particular, phenylacyl analogs were also 6 times more efficient in inhibition of lipid peroxidation in model membranes than anthralin.Structure-activity relationships have shown that the presence of free phenolic groups in the attached aromatic ring is beneficial but not required for 5-LO inhibitory potency.The inhibitory potency in the 10-phenylacyl series increased with the length of the acyl chain with three methylene units being the optimum, suggesting a specific enzyme interaction which would not be expected for nonspecific redox inhibitors.
- Mueller, Klaus,Guerster, Dieter,Piwek, Susanne,Wiegrebe, Wolfgang
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p. 4099 - 4107
(2007/10/02)
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- Process for preparing a naphthalene derivative
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A novel process for preparing a naphthalene derivative of the formula: STR1 wherein R1, R2, R3, R4, R5, R6 and R7 are a lower alkyl group, and an intermediate thereof is disclose
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- A process for preparing a naphthalene derivative
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A novel process for preparing a naphthalene derivative of the formula: wherein R1, R2, R3, R4, R5, R6 and R7 are a lower alkyl group, and an intermediate thereof is disclosed. Said naphthalene derivative (I) and
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- Regioselective Reductive Alkylation of 3,4,5-Trimethoxybenzaldehyde Dimethylacetal: A New Synthesis of 4-Alkyl-3,5-dimethoxybenzaldehydes and 2,5-Dialkyl-1,3-dimethoxybenzenes
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The regioselective replacement of the 4-methoxy group of 3,4,5-trimethoxybenzaldehyde dimethylacetal by an alkyl group under reductive electron-transfer conditions has been employed as a key step in a new synthesis of 2,5-dialkyl-1,3-dimethoxybenzenes via the corresponding 4-alkyl-3,5-dimethoxybenzaldehydes.
- Azzena, Ugo,Cossu, Sergio,Denurra, Teresa,Melloni, Giovanni,Piroddi, Anna Maria
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p. 313 - 314
(2007/10/02)
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