- Formation of Dihydrobenzofurans by Radical Cyclization
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A survey of methods for the generation of aryl radicals from o-alkenyloxyarene diazonium salts demonstrates that dihydrobenzofuran derivatives can be efficiently formed by treatment of (1) or (2) with Bun3SnH-Et2O or with NaI-Me2CO; methods utilising the iodo-compound (3; X = I) are less effective.
- Beckwith, Athelstan L. J.,Meijs, Gordon F.
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- Synthesis of 2-azabicyclo[3.2.2]nonane-derived monosaccharide mimics and their evaluation as glycosidase inhibitors
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The racemic 2-azabicyclo[3.2.2]nonanes 5 and 18 were synthesized and tested as β-glycosidase inhibitors. The intramolecular Diels-Alder reaction of the masked o-benzoquinone generated from 2-(allyloxy)phenol (6) gave the α-keto acetal 7 which was reduced with SmI2 to the hydroxy ketone 8. Dihydroxylation. isopropylidenation (→ 12), and Beckmann rearrangement provided lactam 15. N-Benzylation of this lactam, reduction to the amine 17, and deprotection provided the amino triol 19 which was debenzylated to the secondary amine 5. Both 5 and 19 proved weak inhibitors of snail β-mannosidase (IC50 > 10 mM), Caldocellum saccharolyticum β-glucosidase (IC50 > 10 mM), sweet almond β-glucosidase (IC50 > 10 mM), yeast α-glucosidase (5: IC50 > 10 mM; 19: IC50 = 1.2 mM), and Jack bean α-mannosidase (no inhibition detected).
- Buser, Stephan,Vasella, Andrea
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- Photoresponsive azo-combretastatin A-4 analogues
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Colchicine analogues in which an azo group is incorporated into a molecule containing the key pharmacophore of colchicine, have found particular utility as switchable tubulin binding chemotherapeutics. Combretastatin is a related compound containing a stilbene fragment that shows different bioactivity for the cis and trans isomers. We have performed cell assays on 17 new compounds structurally related to a previously reported azo-analogue of combretastatin. One of these compounds showed enhanced potency against HeLa (IC50 = 0.11 μM) and H157 cells (IC50 = 0.20 μM) for cell studies under 400 nm irradiation and the highest photoactivity (IC50 with irradiation/IC50 in dark = 550). We have performed docking and physicochemical studies of this new compound (7). Kinetic studies in water reveal a longer half-life for the cis isomer of 7 which may be one factor responsible for the better IC50 values in cell assays and the improved photoresponsive behavior.
- Rastogi, Shiva K.,Zhao, Zhenze,Barrett, Scott L.,Shelton, Spencer D.,Zafferani, Martina,Anderson, Hailee E.,Blumenthal, Madeleine O.,Jones, Lindsey R.,Wang, Lei,Li, Xiaopeng,Streu, Craig N.,Du, Liqin,Brittain, William J.
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- Cyclodextrin-Promoted Radical Cyclization of o-(2-Propenyloxy)- and o-(2-Propynyloxy)-benzenediazonium Ions
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Radical dediazoniation of o-(2-propenyloxy)- and o-(2-propynyloxy)benzenediazonium ions in the presence of β-cyclodextrin gives selectively dihydrobenzofurans under N2, while hydroxymethylated dihydrobenzofurans and 3-hydroxymethyl-benzofuran under air, respectively.
- Fukunishi, Koushi,Shimode, Mitsuo,Hisamune, Rie,Akita, Makoto,Kuwabara, Masaki,et al.
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Read Online
- Structure–Activity Relationship of Anti-malarial Allylpyrocatechol Isolated from Piper betle
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Malaria disease remains a serious worldwide health problem. In South-East Asia, one of the malaria infection “hot-spots,” medicinal plants such as Piper betle have traditionally been used for the treatment of malaria, and allylpyrocatechol (1), a constituent of P. betle, has been shown to exhibit anti-malarial activities. In this study, we verified that 1 showed in vivo anti-malarial activity through not only intraperitoneal (i.p.) but also peroral (p.o.) administration. Additionally, some analogs of 1 were synthesized and the structure–activity relationship was analyzed to disclose the crucial sub-structures for the potent activity.
- Horii, Toshihiro,Itagaki, Sawako,Kawano, Tomikazu,Miyoshi, Akihito,Murakami, Nobutoshi,Tamura, Satoru
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p. 784 - 790
(2020/09/18)
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- Hybridization of β-Adrenergic Agonists and Antagonists Confers G Protein Bias
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Starting from the β-adrenoceptor agonist isoprenaline and beta-blocker carvedilol, we designed and synthesized three different chemotypes of agonist/antagonist hybrids. Investigations of ligand-mediated receptor activation using bioluminescence resonance energy transfer biosensors revealed a predominant effect of the aromatic head group on the intrinsic activity of our ligands, as ligands with a carvedilol head group were devoid of agonistic activity. Ligands composed of a catechol head group and an antagonist-like oxypropylene spacer possess significant intrinsic activity for the activation of Gαs, while they only show weak or even no β-arrestin-2 recruitment at both β1- and β2-AR. Molecular dynamics simulations suggest that the difference in G protein efficacy and β-arrestin recruitment of the hybrid (S)-22, the full agonist epinephrine, and the β2-selective, G protein-biased partial agonist salmeterol depends on specific hydrogen bonding between Ser5.46 and Asn6.55, and the aromatic head group of the ligands.
- Stanek, Markus,Picard, Louis-Philippe,Schmidt, Maximilian F.,Kaindl, Jonas M.,Hübner, Harald,Bouvier, Michel,Weikert, Dorothée,Gmeiner, Peter
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p. 5111 - 5131
(2019/05/28)
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- Direct oxidation of the C(sp2)-C(sp3) bond from benzyltrimethylsilanes to phenols
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A novel pathway for direct conversion of benzylsilanes to phenols by oxidation with Na2S2O8 and oxygen is efficiently developed under mild and neutral conditions. The reaction shows good functional group tolerance to afford phenols in moderate yields. The possible mechanism is proposed based on the isotopic labeling trials.
- Li, Wei,Gao, Guolin,Gao, Yuan,Yang, Chao,Xia, Wujiong
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supporting information
p. 5291 - 5293
(2017/07/10)
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- Reagent Design and Ligand Evolution for the Development of a Mild Copper-Catalyzed Hydroxylation Reaction
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Parallel synthesis and mass-directed purification of a modular ligand library, high-throughput experimentation, and rational ligand evolution have led to a novel copper catalyst for the synthesis of phenols with a traceless hydroxide surrogate. The mild reaction conditions reported here enable the late-stage synthesis of numerous complex, druglike phenols.
- Fier, Patrick S.,Maloney, Kevin M.
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supporting information
p. 3033 - 3036
(2017/06/07)
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- Regioselective Alkoxycarbonylation of Allyl Phenyl Ethers Catalyzed by Pd/dppb under Syngas Conditions
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A simple and regioselective synthesis of phenoxy esters and phenylthio esters is reported. The products are obtained by selective alkoxycarbonylation catalyzed by Pd2(dba)3, 1,4-bis(diphenylphisphino)butane (dppb), and syngas (CO/H2) in chloroform/alcohol. This methodology affords bifunctional products in good yield with excellent n-selectivity and without the need to use additives.
- Amézquita-Valencia, Manuel,Alper, Howard
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p. 3860 - 3867
(2016/05/24)
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- Enzymatic allylation of catechols
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Enzymatic allylation of catechols was realized via catechol O-methyltransferase (COMT) using an allylated S-adenosyl- L-methionine (allyl-SAM) analog, with relatively good chemoand regioselectivities. This new reaction offered an alternative procedure for allylation of catechols, which can be expanded as a biocatalytic allylation method in organic synthesis.
- Zhang, Yixin,Liu, Wujun,Sohail, Muhammad,Wang, Xueying,Liu, Yuxue,Zhao, Zongbao K.
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supporting information
p. 949 - 951
(2015/08/24)
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- A smart library of epoxide hydrolase variants and the top hits for synthesis of (S)-β-blocker precursors
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Microtuning of the enzyme active pocket has led to a smart library of epoxide hydrolase variants with an expanded substrate spectrum covering a series of typical β-blocker precursors. Improved activities of 6- to 430-fold were achieved by redesigning the active site at two predicted hot spots. This study represents a breakthrough in protein engineering of epoxide hydrolases and resulted in enhanced activity toward bulky substrates. Hot pockets: Microtuning of the enzyme active pocket gives a smart library of epoxide hydrolase variants with an expanded substrate spectrum covering a series of typical β-blocker precursors. Improved activities of 6- to 430-fold were achieved by redesigning the active site at two predicted hot spots, and enhanced activity toward bulky substrates was found.
- Kong, Xu-Dong,Ma, Qian,Zhou, Jiahai,Zeng, Bu-Bing,Xu, Jian-He
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supporting information
p. 6641 - 6644
(2014/07/08)
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- SUBSTITUTED CATHECHOLS AS INHIBITORS OF IL-4 AND IL-5 FOR THE TREATMENT BRONCHIAL ASTHMA
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The present invention relates to compounds of general formula 1 for the treatment of bronchial asthma by inhibition of IL-4 or IL-5 pathway inhibition. The present invention also relates to the use of compound of general formula 1 for the treatment of bronchial by inhibition of IL-4 or IL-5 pathway. The present invention also relates to the method of treating asthma by inhibition of IL-4 or IL-5 pathway by administration of compound or said composition through oral, intranasal, route or by inhalation to a mammal in need thereof. Compound of general formula 1 may be used for reducing perivascular and peribronchial inflammation.
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Paragraph 0170-0174
(2014/05/20)
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- OXPRENOLOL COMPOSITIONS FOR TREATING CANCER
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The present invention relates to compositions of S-enantiomer enriched oxprenolol and their use in treating cancer and treating or preventing, in cancer patients, cachexia, body weight loss, lean body mass loss and adipose tissue loss, and improving quality of life and prolonging survival of cancer patients.
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Paragraph 0162-0163
(2014/09/29)
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- S-ENANTIOMERICALLY ENRICHED COMPOSITIONS OF BETA BLOCKERS FOR TREATING AMYOTROPHIC LATERAL SCLEROSIS
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The present invention relates to S-enantiomerically enriched compositions of beta blockers and uses thereof, including uses of the beta blocker compositions for treating amyotrophic lateral sclerosis. The beta blocker compositions can also be used for preventing loss of lean mass, preventing body weight loss in subjects, improving quality of life in subjects, and prolonging survival in amyotrophic lateral sclerosis patients. The beta blocker can be oxprenolol or a pharmaceutically acceptable salt thereof.
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Paragraph 0145-0146
(2014/09/29)
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- METHODS AND COMPOSITIONS FOR CONTROL OF GYPSY MOTHS, Lymanria dispar
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The invention provides in part dialkoxybenzene and eugenol compounds for controlling infestation by a Lymantria dispar, and methods thereof. The compounds include a compound of Formula I: where R1 may be methyl, ethyl, propyl, n-butyl, isopentyl (3-methylbutyl) or allyl; R2 may be at positions 2, 3 or 4 and may be H, methyl, ethyl, propyl, n-butyl, isopentyl (3-methylbutyl) or allyl; and R3 may be optionally present at positions 2, 3 and 4, and is allyl; with the provisos that when R2 is at position 2, R3 if present is at position 3, or when R2 is at to position 3, R3 if present is at positions 2 or 4, or when R2 is at position 4, R3 if present is at position 2; or of Formula II: where R1 may be methyl, ethyl, propyl, n-butyl, isopentyl (3-methylbutyl) or allyl; or mixtures thereof.
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Page/Page column 10
(2010/08/07)
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- METHODS AND COMPOSITIONS FOR CONTROL OF CABBAGE LOOPER, Trichoplusia ni
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The invention provides in part dialkoxybenzene compounds for controlling infestation by a Trichoplusia ni, and methods thereof. The compounds include a compound of Formula I: where R1 may be methyl, ethyl, propyl, n-butyl, isopentyl(3-methylbutyl) or allyl; R2 may be at positions 2, 3 or 4 and may be H, methyl, ethyl, propyl, n-butyl, isopentyl(3-methylbutyl) or allyl; and R3 may be optionally present at positions 2, 3 and 4, and is allyl; except that when R2 is at position 2, R3 if present is at position 3, and when R2 is at position 3, R3 if present is at positions 2 or 4, and when R2 is at position 4, R3 if present is at position 2, and when R2 is at position 4 and R3, if present, has reacted with an OH group at position 1 in a Markovnikov sense, then R3 becomes R4, a dihydrofuran.
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Page/Page column 9-10
(2010/07/04)
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- INHIBITORS OF PHOSPHATIDYLINOSITOL-3-KINASE (PI3) AND INDUCERS OF NITRIC OXIDE (NO)
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The present invention relates to compounds of general formula 1 for the treatment of malignancy by inhibition of PI3-Akt pathway and or induction of NO. The present invention also relates to the use of compound of general formula 1 for the treatment of malignancy by inhibition of PI3-Akt pathway and or induction of NO. The present invention further relates to a method of treating malignancy by inhibition of PI3-Akt pathway and or induction of NO by administration of compound or said composition to a mammal in need thereof.
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Page/Page column 19-20
(2010/08/04)
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- Formation of dibenzofurans by flash vacuum pyrolysis of aryl 2-(allyloxy)benzoates and related reactions
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Flash vacuum pyrolysis (FVP) of aryl 2-(allyloxy)benzoates 5 and of the corresponding aryl 2-(allylthio)benzoates 6 at 650°C, gives dibenzofurans 19 and dibenzothiophenes 20, respectively. The mechanism involves generation of phenoxyl (or thiophenoxyl) radicals by homolysis of the O-allyl (or S-allyl) bond, followed by ipso attack at the ester group, loss of CO2 and cyclisation of the resulting aryl radical. Synthetically, the procedure works well for p-substituted substrates, which lead to 2-substituted dibenzofurans 19b-f (73-90%) and dibenzothiophenes 20b-c (90-94%). Little selectivity is shown in the cyclisation of m-substituted substrates and competing interactions of the radical with the substituent - and ipso-attack - complicate the pyrolyses of o-substituted substrates. FVP of related radical precursors including 2-(allyloxy)phenyl benzoates 43 gave no dibenzofurans, whereas 2-(allyloxy-5-methyl)azobenzene 44 gave a much reduced yield. No carbazoles were obtained by FVP of 4-methylphenyl 2-(allylamino)benzoate 42.
- Black, Michael,Cadogan,McNab, Hamish
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body text
p. 2961 - 2967
(2010/09/06)
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- Asymmetric synthesis of O-protected acyloins using enoate reductases: Stereochemical control through protecting group modification
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O-Protected cyclic acyloins were obtained in nonracemic form through asymmetric bioreduction of α,β-unsaturated alkoxy ketones by using 11 different enoate reductases from the "Old Yellow Enzyme" family. The stereochemical outcome of the biotransformation could be switched by variation of the O-protecting group or by the ring size of the substrate, which allows access to both stereoisomers in up to >97 % ee Whereas α-alkoxy enones were readily accepted as substrates, β-analogs were not converted. Overall, α-alkoxy enones represent a novel type of substrate for flavin-dependent ene-reductases. Copyright
- Winkler, Christoph K.,Stueckler, Clemens,Mueller, Nicole J.,Pressnitz, Desiree,Faber, Kurt
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supporting information; experimental part
p. 6354 - 6358
(2011/02/24)
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- Dialkoxybenzene and dialkoxyallylbenzene feeding and oviposition deterrents against the cabbage looper, trichoplusia ni: Potential insect behavior control agents
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The antifeedant, oviposition deterrent, and toxic effects of individual dialkoxybenzene compounds/sets and of hydroxy- or alkoxy-substituted allylbenzenes, obtained through Claisen rearrangement of substituted allyloxybenzenes, were assessed against the cabbage looper, Trichoplusia ni, in laboratory bioassays. Most of the compounds/sets strongly deterred larval feeding, with some exhibiting mild toxic and oviposition deterrent effects as well. Some of the compounds/sets were more active than the commercial insect repellent, DEET (N,N-diethyl-m-toluamide), as both feeding and oviposition deterrents against the cabbage looper. On the basis of the obtained oviposition data a general hypothesis was proposed regarding the oviposition sites: one binding mode with the alkyl and allyl groups on the same side of the benzene ring resulted in deterrence, the other with alkyl and allyl groups on opposite sides of the benzene ring resulted in stimulation. The results suggest some structure-activity relationships useful in improving the efficacy of the compounds and designing new, nontoxic insect control agents for agriculture.
- Akhtar, Yasmin,Yu, Yang,Isman, Murray B.,Plettner, Erika
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scheme or table
p. 4983 - 4991
(2011/08/06)
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- Ring-closing metathesis for the synthesis of novel 9- and 10-membered silicon-containing benzo-fused heterocycles
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A ring-closing metathesis (RCM) strategy afforded a number of novel 9- and 10-membered benzo-fused compounds containing at least one silicon atom as part of the heterocyclic portion. In this manner, the following compounds containing heterocyclic rings of 9-10 atoms were synthesized: (Z)-2,2-dimethyl-7-[(4-methylphenyl)sulfonyl]-2,3,6,7-tetrahydrobenzo[h][1,7,2]oxazasilonine, (Z)-2,2-dimethyl-3,6-dihydro-2H-benzo[h][1,7,2]dioxasilonine, (Z)-8-isopropoxy-9-methoxy-3,3-dimethyl-1,3,4,7-tetrahydrobenzo[g][1,2]oxasilonine and (Z)-2,2,7,7-tetramethyl-2,3,6,7-tetrahydrobenzo[i][1,8,2,7]dioxadisilecine.
- Scalzullo, Stefania M.,Islam, Rafique Ul,Morgans, Garreth L.,Michael, Joseph P.,van Otterlo, Willem A.L.
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body text
p. 7403 - 7405
(2009/05/11)
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- Screening of dialkoxybenzenes and disubstituted cyclopentene derivatives against the cabbage looper, Trichoplusia ni, for the discovery of new feeding and oviposition deterrents
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The antifeedant, oviposition deterrent, and toxic effects of dialkoxybenzene minilibraries and of disubstituted cyclopentene minilibraries (i.e., consisting of four to five compounds) along with their pure constituent compounds were assessed against third instar larvae and adults of the cabbage looper, Trichoplusia ni, in laboratory bioassays in a search for new insect control agents. These compounds mimic naturally occurring bioactive odorants and tastants and are relatively easily prepared from commodity chemicals. Most of these libraries strongly deterred larval feeding, with some exhibiting strong toxic and oviposition deterrent effects as well. Our results suggest some structure-function relationships within these libraries. Replacement of a methyl group with larger alkyl substituents increased the feeding deterrent effects in most cases. The presence of a free hydroxyl group, irrespective of the carbon framework or alkyl substituent, served to reduce feeding deterrent effects in all series of compounds. Further, exceeding a certain group size also generally had a detrimental effect. This information will be useful in designing new insect control agents for agriculture. Some of these libraries and compounds may have potential for development as commercial insecticides.
- Akhtar, Yasmin,Isman, Murray B.,Paduraru, Peggy M.,Nagabandi, Srinivas,Nair, Ranjeet,Plettner, Erika
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scheme or table
p. 10323 - 10330
(2009/10/02)
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- A new and highly effective organometallic approach to 1,2-dehalogenations and related reactions
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We investigated the reductive elimination of several functionalized and non-functionalized vic-dibromides with 1,2-diphenyl-, 1,1,2,2-tetraphenyl- and 1-phenyl-2-(2-pyridyl)-1,2-disodioethane. The reaction, involving some of the less expensive organic and inorganic reagents, proceeds under mild conditions, and is tolerant of a variety of functional groups. Extension of this procedure to similar 1,2-disubstituted compounds was also investigated. Reductive eliminations run on stereochemical probe compounds strongly suggest that this reaction proceeds via a "single electron" reductive elimination reaction pathway.
- Azzena, Ugo,Pittalis, Mario,Dettori, Giovanna,Pisano, Luisa,Azara, Emanuela
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p. 3892 - 3900
(2008/03/12)
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- Investigation of selective mono-deallylation of O,O′-diallylcatechols and 3-methylene-1,5-benzodioxepanes
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Selective mono-deallylation of O,O′-diallylcatechols using 10% Pd/C was investigated to give the corresponding allylphenols. A similar reaction of 3-methylene-1,5-benzodioxepanes afforded O-methacryl catecohols. When substrates bearing various substituents on the benzene ring were subjected to the reaction, regioselective cleavage of an ether bond occurred at the side of para position to an electron-withdrawing group on the aromatic ring. On the other hand, an electron-donating group did not cause any selectivity.
- Hayashida, Maiko,Ishizaki, Miyuki,Hara, Hiroshi
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p. 1299 - 1303
(2008/09/20)
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- Synthesis of 2H-1,5-benzodioxepin and 2,5-dihydro-1,6-benzodioxocin derivatives via ring-closing metathesis reaction
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The synthesis of various 2H-1,5-benzodioxepin and 2,5-dihydro-1,6- benzodioxocin derivatives is described. The key step involves the construction of seven- and eight-membered rings via ring-closing metathesis reaction.
- Mamouni,Soukri,Lazar,Akssira,Guillaumet
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p. 2631 - 2633
(2007/10/03)
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- Integrated Chemical Process: Convenient Synthesis of Enantiopure 2-Hydroxymethyl-1,4-benzodioxane Derivatives under Iterative Catalysis of CsF
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One-pot processes to enantiopure 2-hydroxymethyl-1,4-benzodioxane derivatives have been established under catalysis of CsF. A sequence of O-alkylation of catechols with enantiopure 3-chloro-1,2-propanediol, tosylation of the alcohol, deprotection of the benzyl ether, and intramolecular etherification can be integrated. The O-alkylation is also feasible with enantiopure oxiranes. All reactions, except debenzylation, are catalyzed by a single catalyst, CsF. The hydrogenative deprotection of the benzyl ether with Pd-C is compatible with the CsF-catalyzed reactions. The integrated protocols give rise not only to compaction of the whole processes but also to increases in overall yields.
- Kitaori, Kazuhiro,Furukawa, Yoshiro,Yoshimoto, Hiroshi,Otera, Junzo
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- Highly selective cleavage of prenyl ethers by means of a TiCl4-n-Bu4NI mixed reagent
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Treatment of the prenyl ether of ethyl salicylate with a TiCl4-n-Bu4NI mixed reagent resulted in cleavage of the C-O bond to provide ethyl salicylate in quantitative yield. On the other hand, no cleavage reaction was observed when ethyl p-prenyloxybenzoate was used as a substrate. In this system, the cleavage reaction of ethers proved to be accelerated by the chelating effect of a neighboring group in the substrate.
- Tsuritani, Takayuki,Shinokubo, Hiroshi,Oshima, Koichiro
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p. 8121 - 8124
(2007/10/03)
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- Hydrogen peroxide/boric acid: An efficient system for oxidation of aromatic aldehydes and ketones to phenols
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Hydrogen peroxide activated by boric acid in the presence of sulfuric acid has been shown to be an efficient oxidizing system for direct conversion of aromatic aldehydes and ketones to phenols.
- Roy, Amrita,Reddy,Mohanta, Pramod K.,Ila,Junjappa
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p. 3781 - 3791
(2007/10/03)
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- Synthesis of photosensitive EGTA derivatives
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The syntheses of five derivatives of EGTA and one EGTA analogue are described. These molecules each have an ortho-nitrophenyl substituent positioned such that irradiation will cut the EGTA coordination sphere in two.
- Ellis-Davies, Graham C. R.
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p. 953 - 956
(2007/10/03)
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- Selective deprotection of propargyl ethers using tetrathiomolybdate
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Benzyltriethylammonium tetrathiomolybdate, [PhCH2NEt3]2MoS4, 1 deprotects propargyl ethers of alcohols and phenols in a selective manner in high yields. Easily reducible groups like nitro, aldehyde, keto and allyl are not affected.
- Swamy,Ilankumaran, Palanichamy,Chandrasekaran, Srinivasan
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p. 513 - 514
(2007/10/03)
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- Sequential radical perfluoroalkylation - Nucleophilic cyclization. Synthesis of 2-perfluoroalkylidenemethyl and 2-perfluoroalkylmethyl-1,4-dioxanes from 1-O-allyl-1,2-diols
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The title compounds were synthesized by radical addition of perfluoroalkyl iodide to 1-O-allyl-1,2-diols and subsequent nucleophilic cyclization according to one of the following procedures. Basic treatment of the iodo F-alkyl adduct gave an olefinic compound which is stereoselectively cyclized with an excess of base into the corresponding 2-perfluoroalkylidenemethyl-1,4-dioxane through as S(N)' process. The direct cyclization of the adduct into 2-perfluoroalkylmethyl-1,4-dioxane was achieved by a new and simple method using molecular iodine or positive halogen reagents (DBH, NBS) for the activation of the carbon-iodine bond.
- Foulard, Gaelic,Brigaud, Thierry,Portella, Charles
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p. 6187 - 6200
(2007/10/03)
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- Ring-Closure Reactions. 21. Intramolecular β-Elimination Competing with Ring Formation from o-(ω-Bromoalkoxy)phenoxides over a Wide Range of Ring Sizes
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Unimolecular β-elimination of HBr from the CH2CH2Br end of o--OC6H4O(CH2)n-4Br has been interpreted as an E2-type reaction promoted by the distal phenoxide group acting as a base.Combination of careful product analyses with kinetic data has provided rate constants and effective molarities for intramolecularly assisted elimination reactions occurring through 7-, 8-, 9-, 10-, and 14-membered ring transition states.A comparison is carried out with the competing intramolecular substitution reactions leading to ring formation.Attention is called to the specific entropic and geometrical requirements of intramolecular elimination in which the donor-proton-acceptor arrangement is a part of a cyclic structure.The importance of the present results in the general field of intramolecular acid or base catalysis phenomena is discussed.
- Cort, Antonella Dalla,Mandolini, Luigi,Masci, Bernardo
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p. 3979 - 3982
(2007/10/02)
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