- α-carbonyl radical cyclization approach toward spiro[4.4]nonene: Total synthesis of dimethyl gloiosiphone A
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The total synthesis of dimethyl gloiosiphone A 2 was achieved via an α-carbonyl radical spirocyclization.
- Sha, Chin-Kang,Ho, Wen-Yueh
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- Interconversions of C5H10O+. ions with the oxygen on the first, second and third carbons: Approximately 60 communicating isomers
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The structures of the C4H7O+ and C3H6O+. dissociation products from selected C5H10O+. isomers with the oxygen on the first, second and third carbons were determined. The first product is CH3C(OH)CH=CH2+ and the second is CH3C(OH+)CH2. and CH3.CHCHOH+ in various proportions. These results demonstrate that ions with the oxygen on the first and third carbons isomerize partially to isomers with the oxygen on the second carbon. This and C5H10O+. isomers expected to be accessible to each other suggest that there are traversable pathways between about 60 C5H10O+. isomers, demonstrating how extensive interconversions of aliphatic radical cations can be.
- McAdoo,Hudson
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- Intramolecular cycloadditions of vinylketenes to olefins. Part II. The synthesis of a linear annelated triquinane derivative.
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Regioselective formation of vinylketene 3, followed by its stereoselective intramolecular cycloaddition with an olefin, yielded the linear annelated cis-anti-cis triquinane precursor 1.
- Mesmaeker, Alain De,Veenstra, Siem J.,Ernst, Beat
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- Converting cycloalkanones into N-heterocycles: Formal synthesis of (-)-gephyrotoxin 287C
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The photochemical rearrangement of N-activated lactams enables their ring contraction concomitant with the migration of a carbon onto a nitrogen atom. When coupled with the Beckmann rearrangement, this photochemical ring contraction converts cycloalkanones into N-heterocycles in a few steps and in a stereospecific manner. To showcase the method, we performed an efficient formal synthesis of (-)-gephyrotoxin 287C.
- Pichette, Simon,Winter, Dana K.,Lessard, Jean,Spino, Claude
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- Tertiary Enamide-Triggered SEAr: Domino Allylation and Enamine-Type Addition
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Two unprecedented domino reactions are described, starting from ketospiro-enesulfonamides. By treatment with ZrCl4 and allylsilane, an intramolecular electrophilic aromatic substitution and subsequent allylation is observed. By treatment with TiCl4 and allylsilane, a double enamine-type reaction takes place, thus creating simultaneously four contiguous stereogenic centers diastereoselectively.
- Beltran, Frédéric,Miesch, Laurence
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supporting information
p. 1569 - 1573
(2019/03/12)
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- Mechanistic Study and Development of Catalytic Reactions of Sm(II)
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Samarium diiodide (SmI2) is one of the most widely used single-electron reductants available to organic chemists because it is effective in reducing and coupling a wide range of functional groups. Despite the broad utility and application of SmI2 in synthesis, the reagent is used in stoichiometric amounts and has a high molecular weight, resulting in a large amount of material being used for reactions requiring one or more equivalents of electrons. Although few approaches to develop catalytic reactions have been designed, they are not widely used or require specialized conditions. As a consequence, general solutions to develop catalytic reactions of Sm(II) remain elusive. Herein, we report mechanistic studies on catalytic reactions of Sm(II) employing a terminal magnesium reductant and trimethylsilyl chloride in concert with a noncoordinating proton donor source. Reactions using this approach permitted reductions with as little as 1 mol % Sm. Mechanistic studies provide strong evidence that during the reaction, SmI2 transforms into SmCl2, therefore broadening the scope of accessible reactions. Furthermore, this mechanistic approach enabled catalysis employing HMPA as a ligand, facilitating the development of catalytic Sm(II) 5-exo-trig ketyl olefin cyclization reactions. The initial work described herein will enable further development of both useful and user-friendly catalytic reactions, a long-standing, but elusive goal in Sm(II) chemistry.
- Maity, Sandeepan,Flowers, Robert A.
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supporting information
p. 3207 - 3216
(2019/02/19)
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- Enantioselective Conia-Ene-Type Cyclizations of Alkynyl Ketones through Cooperative Action of B(C6F5)3, N-Alkylamine and a Zn-Based Catalyst
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An efficient and highly enantioselective Conia-ene-type process has been developed. Reactions are catalyzed by a combination of B(C6F5)3, an N-alkylamine and a BOX-ZnI2 complex. Specifically, through cooperative
- Cao, Min,Yesilcimen, Ahmet,Wasa, Masayuki
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supporting information
p. 4199 - 4203
(2019/04/13)
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- Method development for the determination of 1,1-dimethylhydrazine by the high-performance liquid chromatography–mass spectrometry technique
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Unsymmetrical dimethyl hydrazine is highly toxic, carcinogenic compound, widely used for organic synthesis and drug development. Therefore, due to its high reactivity, direct analysis is problematic. Current study proposes to use derivatization reaction t
- Susinskis, Igors,Mekss, Peteris,Hmelnickis, Juris
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p. 352 - 359
(2018/07/31)
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- One-pot sequential 1,4- and 1,2-reductions of α,β-unsaturated δ-lactones to the corresponding δ-lactols with CuCl and NaBH 4 in methanol
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An efficient, one-pot method for the highly chemoselective synthesis of δ-lactols from α,β-unsaturated δ-lactones using CuCl and NaBH4 in methanol was developed. Georg Thieme Verlag Stuttgart. New York.
- Matsumoto, Yasunobu,Yonaga, Masahiro
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supporting information
p. 1764 - 1768
(2014/08/05)
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- Intramolecular reductive ketone-alkynoate coupling reaction promoted by (η2-propene)titanium
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Intramolecular reductive coupling of cycloalkanones tethered to alkynoates in the presence of (η2-propene)titanium was successfully performed to provide hydroxy-esters in a diastereoselective manner. Subsequent lactonization afforded angularly
- Schaefer, Christian,Miesch, Michel,Miesch, Laurence
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supporting information; scheme or table
p. 3253 - 3257
(2012/06/01)
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- Gold-catalyzed 1,3-acyloxy migration/5-exo-dig cyclization/1,5-acyl migration of diynyl esters
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Working three shifts: Polyconjugated δ-diketones are formed stereoselectively in high yields by the gold-catalyzed rearrangement of 1,6-diyn-3-yl esters. This cascade involves a 1,3-sigmatropic acyloxy shift, a 5-exo-dig cyclization of the resulting allenyne, and an unprecedented 1,5-sigmatropic shift of an acyl fragment. The usefulness of the products was shown by an efficient acid-catalyzed transformation into a complex polycyclic framework. Copyright
- Lebuf, David,Simonneau, Antoine,Aubert, Corinne,Malacria, Max,Gandon, Vincent,Fensterbank, Louis
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supporting information; experimental part
p. 6868 - 6871
(2011/08/06)
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- Generation and trapping of cyclopentenylidene gold species: Four pathways to polycyclic compounds
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Cyclopentenylidene gold complexes can easily be formed from vinyl allenes through a Nazarov-like mechanism. Such carbenes may transform in four different ways into polycyclic frameworks: electrophilic cyclopropanation, C-H insertion, C-C migration, or proton shift. We have studied the selectivity of these different pathways and used our findings for the expedient preparation of valuable complex molecules. An application to the total synthesis of a natural product, Δ9(12)-capnellene,is presented. DFT computations were carried out to shed light on the me chanisms.
- Lemiere, Gilles,Gandon, Vincent,Cariou, Kevin,Hours, Alexandra,Fukuyama, Takahide,et al.
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scheme or table
p. 2993 - 3006
(2009/09/04)
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- Photoinduced atom-transfer cyclization of α-iodocycloalkanones bearing an allenyl side chain
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(Chemical Equation Presented) Irradiation of α-iodocycloalkanones bearing an allenyl side chain with a sunlamp effected atom-transfer cyclization to give cyclized products in good yield. A mechanism, involving radical atom-transfer cyclization accompanied
- Lin, Hsien-Hsun,Chang, Wen-Sheng,Luo, Shun-Yuan,Sha, Chin-Kang
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p. 3289 - 3292
(2007/10/03)
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- Enzymatic resolution of bicyclo[n.1.0]alkan-1-ols derivatives: Preparation of optically active α-substituted α-methylcycloalkanones
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Optically active α-methyl α-substituted cycloalkanones are prepared by a chemoenzymatic sequence which involves a Lipozyme-catalyzed transesterification of 1-(chloroacetoxy)bicyclo[n.1.0]alkanes and ring opening of these cyclopropanol derivatives.
- Morisson,Barnier,Blanco
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p. 7749 - 7764
(2007/10/03)
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- The mechanism of directed remote asymmetric reduction of carbonyl groups via homochiral boronate esters
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In order to determine whether the remote asymmetric induction in the reduction of compounds such as 1 and 2 using borane is really controlled by intramolecular chelates of type 3, rather than dioxaborolane oxygenborane chelates of type 12, a study was undertaken to examine related reductions involving the corresponding homochiral acetal 30 and comparative reductions of the dioxaborolane 14 and the acetal 23b.While this study showed that reductions of the dioxaborolane 14 and the acetal 23b with borane and L-Selectride were virtually identical, this result did not necessarily indicate that dioxaborolane oxygens or acetal oxygens were directing borane reduction.However, that the more likely explanation for the remote asymmetric induction observed for 1 and 2 being mediated by complex 3 was confirmed by the fact that the acetal 30 gave no asymmetric induction with borane.A crystal structure of the phenylboronate ester 10 has been carried out.
- Conole, Grainne,Mears, Richard J.,Silva, Harshani De,Whiting, Andrew
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p. 1825 - 1836
(2007/10/02)
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- REACTIONS OF 1,1-DIALKYLDIAZENIUM SALTS WITH KETONE ETHYLHYDRAZONES
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By reaction of dialkyldiazenium salts with ketone ethylhydrazones, we prepared and characterized 3,3-disubstituted 3,4-dihydroformazans for the first time.The composition of the reaction mixtures indicates a lower (as compared with aldehyde hydrazones) reactivity of ketone hydrazones.
- Kuznetsov, M. A.,Kuznetsova, L. M.,Zasukhina, E. A.
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p. 1363 - 1366
(2007/10/02)
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- Selective Cleavage of Dimethylhydrazones to the Carbonyl Compounds Using Silica Gel and its Application in the Synthesis of (Z)-9-Tetradecenyl Acetate
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A new method for the selective hydrolytic cleavage of dimethylhydrazones consists of treatment of the hydrazones with silica gel (pH 6.80) in wet tetrahydrofuran.Utilizing this method as one of the key steps, (Z)-9-tetradecenyl acetate, the pheromone of Spodoptera frugiperda, was synthesized.
- Mitra, R. B.,Reddy, G. Bhaskar
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p. 694 - 698
(2007/10/02)
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- CO-OLIGOMERISATION DE BUTADIENE ET D'HETERODIENES AZOTES CATALYSEE PAR LE NICKEL CONTROLE DE LA SELECTIVITE
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Nickel (0) catalysed co-oligomerization of butadiene with heterodienes and hetero-olefins is described.It is shown how the selectivity of these reactions can be controlled by the position of the heteroatom in the heteropartner and also by the nature of th
- Brun, P.,Tenaglia, A,Waegell, B
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p. 5019 - 5030
(2007/10/02)
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