- Primary Anion–π Catalysis of Epoxide-Opening Ether Cyclization into Rings of Different Sizes: Access to New Reactivity
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The concept of anion–π catalysis focuses on the stabilization of anionic transition states on aromatic π surfaces. Recently, we demonstrated the occurrence of epoxide-opening ether cyclizations on aromatic π surfaces. Although the reaction proceeded through unconventional mechanisms, the obtained products are the same as those from conventional Br?nsted acid catalysis, and in agreement with the Baldwin selectivity rules. Different mechanisms, however, should ultimately lead to new products, a promise anion–π catalysis has been reluctant to live up to. Herein, we report non-trivial reactions that work with anion–π catalysis, but not with Br?nsted acids, under comparable conditions. Namely, we show that the anion–π templated autocatalysis and epoxide opening with alcoholate–π interactions can provide access to unconventional ring chemistry. For smaller rings, anion–π catalysis affords anti-Baldwin oxolanes, 2-oxabicyclo[3.3.0]octanes, and the expansion of Baldwin oxetanes by methyl migration. For larger rings, anion–π templated autocatalysis is thought to alleviate the entropic penalty of folding to enable disfavored anti-Baldwin cyclizations into oxepanes and oxocanes.
- Matile, Stefan,Paraja, Miguel
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supporting information
p. 6273 - 6277
(2020/02/28)
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- Convenient Syntheses of Chiral Cyclic Sulfinates (Sultines) from Unsaturated Alcohols
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The reaction of unsaturated alcohols with N-sulfinyl-p-toluenesulfonamide (TsNSO) is shown to lead stereoselectively to chiral cyclic or bicyclic sulfinates (sultines).The reactions occur at ambient temperatures and afford a general route to δ and ε-sultines which are notable for their crystallinity and thermal stability.These studies confirm the preservation of stereochemical integrity of the carbon atom α to the oxygen atom in the sultine ring.Some unsaturated aldehydes furnish sultines via a tandem oxo-ene cyclization and subsequent ring closure to the sultine.In some reactions, N-toluenesulfonamide derivatives of sultines (compounds of type 11) were isolated, and since those were converted into the sultines by the action of BF3*OEt2, such sulfonamides are considered to be intermediates in the reaction pathway.
- Marson, Charles M.,Giles, Paul R.
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p. 8067 - 8073
(2007/10/03)
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- Organomolybdenum and Organotungsten Reagents, III. Selective, Nonbasic Carbonylmethylenation Reagents from MoOCl3(THF)2 and MoOCl4: Formation, Thermolability, Structure
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From the family of more than 20 carbonylolefinating μ-methylene molybdenum and tungsten complexes the reagent "3", obtained in solution by treatment of MoOCl3(THF)2 with two equivalents of methyllithium, is probably the most favorable one for chemoselective carbonylolefination reactions.As judged by the 13C- and 1H-NMR spectra the reagent is not a single species, but a mixture of either isomeric 1,3-dioxo-1,3-dimolybda(V)cyclobutane complexes 3, differing in the position of the ligands Cl, O, and THF at the molybdenum atoms, or of oligomers of 3. - Treatment of MoOCl4 with two equivalents of methyllithium gave a carbonylolefinating reagent "4" which, according to NMR data, consists of isomeric or oligomeric 1,3-dioxo-1,3-dimolybda(VI)cyclobutane complexes 4.Both reagents are labile at room temperature, but differ from the classical carbonylolefinating reagents by an acidic rather than a basic character, resistance to hydroxy groups, and high selectivity. Key Words: Carbonylolefination / μ-Methylene complexes / Molybdenum reagent
- Kauffmann, Thomas,Fiegenbaum, Petra,Papenberg, Michael,Wieschollek, Raphael,Wingbermuehle, Dorothea
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- Asymmetric Catalysis by Chiral Titanium Perchlorate for Carbonyl-Ene Cyclization
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The chiral binaphthol-derived titanium perchlorate (or triflate) is shown to serve efficiently as an asymmetric catalyst for the ene cyclization of type exo,exo and exo',exo involving α-alkoxy aldehyde as an internal enophile to afford the 6- and 7-membered cyclic ethers in high enantiomeric purity.
- Mikami, Koichi,Sawa, Eiji,Terada, Masahiro
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p. 1403 - 1412
(2007/10/02)
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- ELECTROSYNTHESIS OF ALCOHOLS FROM ORGANIC HALIDES AND KETONES OR ALDEHYDES
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The electrosynthesis of a wide range of alcohols from organic halides and ketones or aldehydes is achieved under simple and mild conditions in an undivided electrolytic cell using different sacrificial anodes.
- Sibille, Soline,d'Incan, Esther,Leport, Louis,Perichon, Jacques
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p. 3129 - 3132
(2007/10/02)
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- ELECTROCHEMICAL ADDITIONS OF THE ALLYL AND THE BENZYL GROUPS OF ALLYL AND BENZYL HALIDES TO ACETONE.
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Electrolysis of allyl chloride and five molar excess of acetone in hexamethylphosphoric triamide containing 0. 5 M tetrabutylammonium perchlorate gave an addition product, 2-methyl-4-penten-2-ol, in a 53% yield. Allyl groups of 1-chloro-2-methyl-2-propene, 1-chloro-2-butene(3), 3-chloro-1-butene(4), 1-chloro-3-methyl-2-butene(5), and 3-chloro-3-methyl-1-butene(6), and benzyl groups of benzyl chloride, benzyl bromide, and 1-chloro-1-phenylethane can similarly be added to acetone by electrolysis to give the corresponding alcohols in fair to good yields. Among these electrochemical reactions, those of 3, 4, 5 and 6 with acetone give respectively two isomeric homoallyl alcohols, one of the isomers is not accessible by the usual chemical reaction between allylic organometallics and acetone.
- Satoh,Suginome,Tokuda
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p. 1791 - 1794
(2007/10/02)
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- Studies on the Conversions of Diols and Cyclic Ethers. Dehydration of Alcohols and Diols on the Action of Dimethylsulfoxide
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The transformations of 13 alcohols and 13 diols in the presence of a small amount dimethylsulfoxide (1/16 mol) were studied.Relationships were found between the type of the hydroxy compound and the selectivity of the transformation, and conclusions were drawn regarding the transformation mechanism.The ether formation observed with certain alcohols proceeds via a carbenium cation.The reaction conditions applied were found suitable for including water elimination from the ditertiary 1,2- and 1,3-diols (pinacol rearrangement, 1,2-elimination).From the 1,4- and 1,5-diols the corresponding oxacycloalkanes can be obtained in good yield.Cyclodehydration occurs by intramolecular nucleophilic substitution, via a concerted mechanism.The effect of DMSO is excerted directly, and proton-catalysis occurs simultaneously.
- Molnar, Arpad,Bartok, Mihaly
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p. 389 - 398
(2007/10/02)
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- Oxymetallation. Part 12. Further Syntheses of Monocyclic Peroxides via Peroxymercuriation
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The scope of cycloperoxymercuriation as a route to monocyclic peroxides has been investigated by studying the reaction of mercury(II) nitrate with ten representative dienes plus hydrogen peroxide, and with two alkenyl hydroperoxides.By hydrogeno- and bromo-demercuriation of the resultant products, seven new methyl- and bromomethyl-substituted 1,2-dioxacyclo-pentanes and -hexanes have been prepared.The geometrical isomers of three of the 1,2-dioxacyclopentanes (4), (8), and (9) have been separated and assigned cis and trans configurations, and each of the four diastereoisomers of 4-bromo-3-bromomethyl-5-methyl-1,2-dioxacyclopentane (11) has been isolated.Two diastereoisomers of 4-bromo-6-bromomethyl-3-methyl-1,2-dioxacyclohexane (13) are formed and have been separated; their 1H n.m.r. spectra indicate that each has a chair conformation with equatorial methyl and bromomethyl groups, the stereoisomerism arising from the disposition of the bromine substituent.The by-products of peroxymercuriation-reduction have been shown to be unsaturated alcohols whose formation is strongly favoured where the cycloperoxymercurial contains an endocyclic mercurio-substituent.
- Bloodworth, A. J.,Khan, Jamil A.
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p. 2450 - 2457
(2007/10/02)
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