- Enantiopure encaged Verkade's superbases: Synthesis, chiroptical properties, and use as chiral derivatizing agent
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Verkade's superbases, entrapped in the cavity of enantiopure hemicryptophane cages, have been synthesized with enantiomeric excess (ee) superior to 98%. Their absolute configuration has been determined by using electronic circular dichroism (ECD) spectros
- Yang, Jian,Chatelet, Bastien,Hérault, Damien,Dufaud, Véronique,Robert, Vincent,Grass, Stéphane,Lacour, Jér?me,Vanthuyne, Nicolas,Jean, Marion,Albalat, Muriel,Dutasta, Jean-Pierre,Martinez, Alexandre
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p. 139 - 146
(2019/12/27)
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- N-Heterocyclic Carbene Iron(III) Porphyrin-Catalyzed Intramolecular C(sp3)–H Amination of Alkyl Azides
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Metal-catalyzed intramolecular C?H amination of alkyl azides constitutes an appealing approach to alicyclic amines; challenges remain in broadening substrate scope, enhancing regioselectivity, and applying the method to natural product synthesis. Herein we report an iron(III) porphyrin bearing axial N-heterocyclic carbene ligands which catalyzes the intramolecular C(sp3)–H amination of a wide variety of alkyl azides under microwave-assisted and thermal conditions, resulting in selective amination of tertiary, benzylic, allylic, secondary, and primary C?H bonds with up to 95 % yield. 14 out of 17 substrates were cyclized selectively at C4 to give pyrrolidines. The regioselectivity at C4 or C5 could be tuned by modifying the reactivity of the C5–H bond. Mechanistic studies revealed a concerted or a fast re-bound mechanism for the amination reaction. The reaction has been applied to the syntheses of tropane, nicotine, cis-octahydroindole, and leelamine derivatives.
- Shing, Ka-Pan,Liu, Yungen,Cao, Bei,Chang, Xiao-Yong,You, Tingjie,Che, Chi-Ming
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p. 11947 - 11951
(2018/09/11)
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- Triiodide-Mediated δ-Amination of Secondary C?H Bonds
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The Cδ?H amination of unactivated, secondary C?H bonds to form a broad range of functionalized pyrrolidines has been developed by a triiodide (I3?)-mediated strategy. By in situ 1) oxidation of sodium iodide and 2) sequestration of the transiently generated iodine (I2) as I3?, this approach precludes undesired I2-mediated decomposition which can otherwise limit synthetic utility to only weak C(sp3)?H bonds. The mechanism of this triiodide-mediated cyclization of unbiased, secondary C(sp3)?H bonds, by either thermal or photolytic initiation, is supported by NMR and UV/Vis data, as well as intercepted intermediates.
- Wappes, Ethan A.,Fosu, Stacy C.,Chopko, Trevor C.,Nagib, David A.
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p. 9974 - 9978
(2016/08/16)
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- Synthesis and in vitro antibacterial evaluation of novel 4-substituted 1-menthyl-1,2,3-triazoles
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Menthyl 1,4-disubstituted 1,2,3-triazole derivatives of hydroxybenzaldehydes, phenols and bile acids were synthesized via click chemistry. The novel synthesized compounds were evaluated for their in vitro antibacterial activity against Enterococcus faeciu
- Khaligh, Pooneh,Salehi, Peyman,Bararjanian, Morteza,Aliahmadi, Atousa,Khavasi, Hamid Reza,Nejad-Ebrahimi, Samad
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p. 1589 - 1596
(2016/11/09)
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- Enantioselective Rhodium(I)-Catalyzed Additions of Arylboronic Acids to N-1,2,3-Triazole-Isatin Derivatives: Accessing N-(1,2,3-Triazolmethyl)-3-hydroxy-3-aryloxindoles
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Oxindoles and triazoles are very privileged frameworks in medicinal chemistry, and thus for the first time we report a catalytic asymmetric route that affords hitherto unknown families of N-(1,2,3-triazolmethyl)-3-hydroxy-3-phenyloxindoles using cheap bio
- Marques, Carolina S.,Burke, Anthony J.
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p. 3518 - 3526
(2016/11/29)
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- Diastereoselective desymmetrization of diarylphosphinous acid-borane amides under Birch reduction
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Treatment of diarylphosphinous acid-borane amides possessing chiral amido functionality with an alkali metal solution in liquid ammonia induced a preferential dearomatization of one aryl substituent at phosphorus leading to the formation of non-equimolar amounts of diastereomers. Diastereoselectivity of dearomatization depends strongly on the structure of a chiral auxiliary.
- Stankevi?, Marek
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p. 6082 - 6102
(2015/06/08)
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- Synthesis and structures of (-) menthyl and (+) neomenthyl substituted enantio pure bis(1,2,3-triazol-5-ylidene)PdI2 complexes and PEPPSI type (1,2,3-triazol-5-ylidene) (pyridine)PdI2complexes. Comparison of catalytic activities for C-C coupling
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(-) Menthol was converted to 1-menthyl-3-methyl-4-phenyltriazolium iodide and 1-neomethyl-3-methyl-4-phenyltriazolium iodide in four steps. These triazolium salts that are enantio pure but diastereo isomers, served as precursors for the synthesis of the corresponding enantio pure bis(1,2,3-triazol-5-ylidene)PdI2 complexes with menthyl and neomenthyl wing tip groups. The palladium complexes were synthesized in high yields using a recently developed mild method under base free and silver free conditions at ambient temperature. These triazolium salts also served as precursors for the synthesis of the corresponding enantio pure PEPPSI type (1,2,3-triazol-5-ylidene) (pyridine)PdI2 complexes. All the complexes were thoroughly characterized by spectroscopic and single crystal XRD data. The relative catalytic activities of these complexes were compared for Suzuki-Miyaura C-C coupling.
- Mohan, Arumugam,Ramkumar, Venkatachalam,Sankararaman, Sethuraman
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p. 115 - 121
(2015/10/12)
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- Studies on synthesis of novel triazolalkyl tagged trifluoromethyl substituted pyrimidine derivatives and their evaluation for cytotoxic activity
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The 2-amino-6-trifluoromethyl-3H-pyrimidin-4-one 1 was propargylated to give two regioisomers 2, 3 in definite proportions. Both regioisomers 2 and 3 were independently reacted with alkyl, aryl or cycloalkyl substituted azides under Sharpless conditions a
- Nagender, Punna,Reddy, Gannarapu Malla,Kumar, Royya Naresh,Reddy, Anugu Chandrashekar,Velatooru, Loka Reddy,Pamanji, Rajesh,Rao, Janapala Venkateswara,Narsaiah, Banda
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p. 865 - 871
(2013/12/04)
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- Practical synthesis of optically pure menthylamines starting from racemic neomenthol
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A reliable and scalable route to racemic and highly enantiomerically enriched menthylamines exploits the technical product rac-neomenthol as the starting material. The elaborated protocol is based on nucleophilic substitution of the hydroxy moiety by azide. Subsequent reduction and resolution with tartaric acid provides the desired optically enriched menthylamines.
- Welschoff, Nina,Waldvogel, Siegfried R.
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experimental part
p. 3596 - 3601
(2010/12/19)
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- Stereoretentive halogenations and azidations with titanium(IV) enabled by chelating leaving groups
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Titaniumdoes it again! With the help of nucleophile-assisting leaving groups (NALGs), alkyl bromides, iodides, and, for the first time, azides are obtained from sulfonates withcomplete retention of configuration. Critical to the design of these new titanium(IV) reactions has been the use of NALGs which are thought to chelate the Lewis acid reagent in the transition state promoting an SNi-type mechanism. (Chemical Equation Presented)
- Lepore, Salvatore D.,Mondal, Deboprosad,Song, Ye Li,Bhunia, Anjan K.
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supporting information; body text
p. 7511 - 7514
(2009/03/12)
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- Oxidation of azides by the HOF·CH3CN: A novel synthesis of nitro compounds
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The HOF·CH3CN complex, readily prepared by passing F 2 through aqueous acetonitrile, is an exceptionally efficient oxygen transfer agent. It is unique in its capacity to oxidize various azides into the corresponding nitro derivatives. This method requires short reactions times and room temperature or below, and the desired nitro compounds were usually isolated in very good yields. The respective nitroso derivatives are believed to be the intermediates in this reaction. Functional groups such as aromatic rings, ketones, nitriles, halides, alcohols, and esters are tolerated. Sulfides react with HOF·CH3CN usually at the same rate as azides. Amines and olefins, however, react faster, so they have to be protected first. Nitro derivatives with various oxygen isotopes can be made using the labeled H 18OF·CH3CN. In the case of chiral azides the stereochemistry around the nitrogen-bonded carbons is retained.
- Carmeli, Mira,Rozen, Shlomo
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p. 4585 - 4589
(2007/10/03)
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- Nicotinoyl azide (NCA)-mediated Mitsunobu reaction: An expedient one-pot transformation of alcohols into azides
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A practical and simple method that allows preparation of azides from alcohols is described. The process involves oxyphosphonium-type activation and it is based upon the use of nicotinoyl azide (NCA), a cheap and easily accessible azide ion source.
- Papeo, Gianluca,Posteri, Helena,Vianello, Paola,Varasi, Mario
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p. 2886 - 2892
(2007/10/03)
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- The Hendrickson reagent and the Mitsunobu reaction: A mechanistic study
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The alkoxytriphenylphosphonium ion intermediate of the Mitsunobu reaction can be generated using the Hendrickson reagent, triphenylphosphonium anhydride trifluoromethanesulfonate, 1. Strangely, while the reagent 1 can be used in place of the Mitsunobu reagents (triphenylphosphine and a dialkylazodicarboxylate) for the esterification of primary alcohols, secondary alcohols such as menthol undergo elimination. Evidence is presented to show that this unexpected result is due to the presence of trialkylammonium triflate salts. Such salts lead to a dramatic decrease in the rate of esterification relative to competing elimination. The Mitsunobu esterification of menthol with p-nitrobenzoic acid was re-examined and the occurrence of elimination reported for the first time. The presence of traces of tetrabutylammonium triflate led to a dramatic reduction in the yield of inverted ester and a corresponding increase in the yield of anti elimination product 2-menthene. The mechanism of the Mitsunobu reaction is discussed in the light of the dramatic salt effect on both the rate and outcome of the reaction and the possible involvement of ion pair clustering. In contrast, use of the reagent 1 resulted in syn elimination to give a 1:2 mixture of 2- and 3-menthenes. Finally, 1 and sodium azide can be used to convert a primary alcohol into an azide in high yield. There was no reaction under Mitsunobu conditions.
- Elson, Kathryn E.,Jenkins, Ian D.,Loughlin, Wendy A.
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p. 2958 - 2965
(2007/10/03)
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- A new novel and practical one pot methodology for conversion of alcohols to amines
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A convenient and efficient one pot sequence has been developed for the transformation of alcohols to amines using sodium azide, triphenylphosphine in CCl4-DMF.
- Vidya Sagar Reddy,Venkat Rao,Subramanyam,Iyengar
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p. 2233 - 2237
(2007/10/03)
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- Chloromethanesulfonate as an efficient leaving group: Rearrangement of the carbon-carbon bond and conversion of alcohols into azides and nitriles
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The chloromethanesulfonate (monochlate) served as an efficient leaving group for rearrangement of the carbon-carbon bond and conversion of alcohols into azides and nitriles. The treatment of the monochlate 16a with zinc acetate in dioxane at 90 °C effected migration of the 4α-methyl group to give alkene 17a. Upon similar treatment of the monochlates 22a, 25a, 28a, and 31a with zinc acetate, the carbon-carbon bonds antiperiplanar to the hydroxyl groups efficiently migrated to afford the alkenes 23a, 26a-c, 29a,b, and 32a, respectively. In the case of the diol 40, the monochlate was converted into the ketone 41 via a rearrangement-ring expansion. The reaction of the monochlates 44a, 47a, 49a, 52a, and 57a with sodium azide or lithium azide in N,N-dimethylformamide efficiently afforded the azides with inversion of the configuration. The introduction of a nitrile group to the sterically hindered alcohol 59 was performed in high yield by the reaction of the monochlate 60a with sodium cyanide.
- Shimizu, Takeshi,Ohzeki, Tomoya,Hiramoto, Katsuya,Hori, Nobuyuki,Nakata, Tadashi
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p. 1373 - 1385
(2007/10/03)
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- A simple and convenient synthesis of alkyl azides under mild conditions
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Various primary and secondary alkyl azides have been synthesized in high yields by the fluoride anion induced S(N)2 substitution reactions of the corresponding alkyl halides, phosphates, or tosylates and trimethylsilyl azide.
- Ito,Koyakumaru,Ohta,Takaya
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p. 376 - 378
(2007/10/02)
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- Zinc Azide Mediated Mitsunobu Substitution. An Expedient Method for the One-Pot Azidation of Alcohols
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In the presence of the diisopropyl azodicarboxylate/triphenylphosphine couple, alcohols react with zinc azide/bis-pyridine complex to give various azides via a Mitsunobu-type substitution.
- Viaud, Marie Claude,Rollin, Patrick
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p. 130 - 132
(2007/10/02)
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- NUCLEOPHILIC INVERSIONS OF A CHIRAL ALCOHOL MEDIATED BY ZINC SALTS
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In a model study, various zinc salts are shown to behave as efficient nucleophilic reagents in mild conditions for unequivocal inversion of (-) menthol to (+) neomethyl derivatives.
- Rollin, Patrick
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p. 611 - 616
(2007/10/02)
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