- Synthesis of 1-Pyrroline by Denitrogenative Ring Expansion of Cyclobutyl Azides under Thermal Conditions
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We herein report an efficient and systematic synthesis of 1-pyrrolines from cyclobutyl azides under thermal and neutral conditions. The reaction proceeded without any additional reagents, and nitrogen was generated as the sole by-product. Furthermore, the generated 1-pyrrolines could be continuously transformed into pyrroles, N-Boc-amines, and oxaziridines in an one-pot manner. (Figure presented.).
- Ban, Kazuho,Miki, Yuya,Sajiki, Hironao,Sawama, Yoshinari,Tomita, Naohito
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supporting information
p. 3481 - 3484
(2021/06/17)
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- Electro-mediated PhotoRedox Catalysis for Selective C(sp3)–O Cleavages of Phosphinated Alcohols to Carbanions
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We report a novel example of electro-mediated photoredox catalysis (e-PRC) in the reductive cleavage of C(sp3)?O bonds of phosphinated alcohols to alkyl carbanions. As well as deoxygenations, olefinations are reported which are E-selective and can be made Z-selective in a tandem reduction/photosensitization process where both steps are photoelectrochemically promoted. Spectroscopy, computation, and catalyst structural variations reveal that our new naphthalene monoimide-type catalyst allows for an intimate dispersive precomplexation of its radical anion form with the phosphinate substrate, facilitating a reactivity-determining C(sp3)?O cleavage. Surprisingly and in contrast to previously reported photoexcited radical anion chemistries, our conditions tolerate aryl chlorides/bromides and do not give rise to Birch-type reductions.
- Barham, Joshua P.,K?nig, Burkhard,Karl, Tobias A.,Reiter, Sebastian,Tian, Xianhai,Yakubov, Shahboz,de Vivie-Riedle, Regina
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p. 20817 - 20825
(2021/08/18)
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- Synthesis of multi-substituted cyclobutanes and alkylidenecyclobutanes by the reaction of cyclobutylmagnesium carbenoids with nucleophiles
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Treatment of 1-chlorocyclobutyl p-tolyl sulfoxides with Grignard reagents such as ethylmagnesium chloride, isopropylmagnesium chloride, and cyclopentylmagnesium chloride in THF at low temperature gave cyclobutylmagnesium carbenoids in high yields. The gen
- Satoh, Tsuyoshi,Kasuya, Takashi,Ishigaki, Masashi,Inumaru, Mio,Miyagawa, Toshifumi,Nakaya, Nobuhito,Sugiyama, Shimpei
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experimental part
p. 397 - 408
(2011/04/15)
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- Catalytic reduction of phenyl-conjugated acetylenic halides by nickel(I) salen: Cyclization versus coupling
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Cyclic voltammetry and controlled-potential electrolysis were employed to study the catalytic reduction of five phenyl-conjugated haloalkynes by nickel(I) salen electro-generated at carbon cathodes in dimethylformamide containing tetramethylammonium tetrafluoroborate. Electrocatalytic reduction of 7-bromo- and 7-iodo-1-phenyl-1-heptyne affords the carbocyclic product, benzylidenecyclohexane, in up to 41 % yield, whereas under similar conditions reduction of 5-halo-1-phenyl-1-pentyne and 8-bromo-1-phenyl-1-octyne gives benzylidenecyclobutane and benzylidenecycloheptane, respectively, in very low yield (≤1 %). Dimers, alkynes, and alkenynes are other products formed from the phenyl-conjugated haloalkynes. Dimers (diphenylalkadiynes) derived from 5-halo-1-phenyl-1-pentyne and 8-bromo-1-phenyl-1-octyne are obtained in yields ranging from 85 to 93 %, whereas 1,14-diphenyltetradeca-1,13-diyne (the dimer produced from 7-halo-1-phenyl-1-heptyne) is found in yields of 45-51 %. To account for the formation of the various products, a mechanistic scheme that involves phenyl-conjugated alkynyl radicals arising from nickel(I) salen catalyzed cleavage of the carbon-halogen bond of each substrate was formulated. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Mubarak, Mohammad S.,Jennermann, Theodore B.,Ischay, Michael A.,Peters, Dennis G.
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p. 5346 - 5352
(2008/03/14)
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- Enantioselective synthesis of 2-aryl cyclopentanones by asymmetric epoxidation and epoxide rearrangement
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(Chemical Equation Presented) Optically active epoxides are prepared by the highly enantioselective epoxidation of benzylidenecyclobutanes using a glucose-derived ketone as the catalyst and oxone as the oxidant. A subsequent Lewis acid catalyzed rearrange
- Shen, Yu-Mei,Wang, Bin,Shi, Yian
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p. 1429 - 1432
(2007/10/03)
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- Cyclizations during the Grignard Reactions of ω-Bromoalkynes
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The Grignard reactions of a number of ω-bromoalkynes have been shown to undergo regioselective cyclizations in certain instances to give the smaller possible carbocycle. These cyclizations are shown to result from two competing processes, whose relative efficiencies depend upon the chain length and the remote substitutent on the acetylene. These are interpreted as a radical cyclization which occurs only during the time the Grignard is being formed from the bromide and an organometallic reaction which slowly transforms the Grignard reagent into its cyclic isomer. The mechanistic details of these transformations are discussed.
- Crandall, Jack K.,Michaely, William J.,Collonges, Francois,Nelson, Deanna J.,Ayers, Timothy A.,Gajewski, Joseph J.
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p. 1473 - 1490
(2007/10/03)
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- Zinc-promoted reactions. 8. The effect of ring strain in the reduction of 1,2-dibenzoylcycloalkanes
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Ring cleavage was the main route in the Zn reduction of 1 in neat AcOH, while selective carbonyl reduction predominated in the presence of LiCl. The less strained 2 underwent only carbonyl reduction with Zn/AcOH. The Clemmensen reduction of both 1 and 2 resulted mainly in acyclic products. The unstrained 3 was fairly resistant towards reduction, and did not undergo ring cleavage.
- Di Vona, Maria Luisa,Luchetti, Luciana,Rosnati, Vittorio
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p. 2949 - 2954
(2007/10/02)
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- Cyclization of acetylenic alkyllithiums
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The scope and limitations of cyclization reactions involving acetylenic alkyllithiums, which were prepared at-78 °C by lithium-iodine exchange between the corresponding iodide and tert-butyllithium in a solution of n-pentane-diethyl ether (3:2 by volume), have been investigated. 4-Pentynyllithiums, 5-hexynyllithiums, and 6-heptynyllithiums bearing a phenyl or trimethylsilyl substituent on the triple bond undergo regiospecific exo-dig cyclization to give 4-, 5-, and 6-membered rings, respectively, bearing an exocyclic lithiomethylene moiety. Cyclization of the analogous alkyl-substituted acetylenic alkyllithiums seems to be confined to the 5-exo mode. The vinyllithium products of the cyclizations may be trapped by reaction with electrophiles to afford functionalized cycloalkylidene derivatives in good yield. The cyclization reactions were found to be highly stereoselective: intramolecular addition of the C-Li unit to the triple bond to produce 4- or 5-membered rings proceeds in a syn fashion to generate isomerically pure exocyclic vinyllithiums that may be functionalized to give stereoisomerically pure products. At the higher temperatures needed to effect cyclization of 6-heptynyllithiums, the initially formed (Z)-vinyllithium intermediate is isomerized to the more stable E-isomer which, when trapped with an electrophile, affords stereoisomerically pure product formally derived from anti addition to the triple bond.
- Bailey, William F.,Ovaska, Timo V.
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p. 3080 - 3090
(2007/10/02)
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- 1,2-Hydrogen migration and alkene formation in the photoexcited states of alkylphenyldiazomethanes
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Laser flash photolysis of alkylphenyldiazomethanes in the presence of pyridine produces easily detected ylides. The data indicate that photolysis of alkylphenyldiazomethanes leads to both carbene formation and direct formation of rearrangement products which do not derive from relaxed carbene intermediates.
- ?elebi, Sol,Leyva, Soccoro,Modarelli, David A.,Platz, Matthew S.
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p. 8613 - 8620
(2007/10/02)
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- Carbocycle Formation via Intramolecular Insertion of Alkynes into Titanium-Carbon Bonds
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Treatment of alkyl titanocene chloride complexes with the Lewis acids EtAlCl2 or Me2AlCl resulted in intramolecular insertion of a tethered alkyne into the Ti-C bond.Regioselective alkyne insertion produced exocyclic trisubstituted alkene products resulting from four-, five-, and six-membered ring formation.In the case of cyclohexane formation, the alkyne was found to insert with syn stereoselectivity.
- Harms, Arthur E.,Stille, John R.
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p. 6565 - 6568
(2007/10/02)
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- Synthesis, Structure, and Reactions of Stable Titanacyclopentanes
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Titanacyclic compounds of the formula Cp*2Ti(CH2CH2C(CH2CHR)CH2) (5a; R=H and 5b; R=C6H5, Cp*=pentamethylcyclopentadienyl), the first stable titanacyclopentanes, have been prepared by the reaction of bis(pentamethylcyclopentadienyl)titanium-ethylene complex (3) with methylenecyclopropanes (4), and their structures were determined based on both spectroscopic data and X-ray crystallography.Complex 5b crystallized in space group P21/a (Z=4) with cell constants, a=21.832(3), b=8.580(1), c=14.759(2) Angstroem, β=96.81(1) deg, U=2744.9(6) Angstroem3 (4261 reflections, R=0.053).The reaction of 5 with carbon monoxide afforded spiroheptan-5-ones in 98percent yield.The thermal decomposition of 5 has been investigated, and possible mechanisms of the reactions have been proposed based on deuterium-labeled experiments.A novel formal reductive elimination of organic ligands giving 1-phenylspirohexane has been observed in the thermolysis of 5b.A structure-reactivity relationship has been discussed.
- Mashima, Kazushi,Sakai, Nozomu,Takaya, Hidemasa
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p. 2475 - 2483
(2007/10/02)
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- INTRAMOLECULAR ADDITION OF ALKYLLITHIUMS TO ACETYLENES: REGIOSPECIFIC 4-, 5-, and 6-EXO-DIG CYCLIZATIONS
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Primary acetylenic alkyllithiums bearing a phenyl substituent on the triple bond, which may be prepared in virtually quantitative yield by low-temperature lithium-iodine interchange, undergo regiospecific exo-dig cyclization via stereoselective syn-additi
- Bailey, William F.,Ovaska, Timo V.
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p. 627 - 630
(2007/10/02)
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- Synthesis and Addition Reactions of 2-Phenyl-1-cyclopropene-1-carboxylates
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From the olefins 1, 2, and 4 - 7 the 1-chloro-1-cyclopropanecarboxylic acids 15 - 20 are prepareded via the dichlorocyclopropanes 8, 9, and 11 - 14.The trans-isomers 15a - 20a were readily separated.Spiropentane 10 undergoes anionic ring cleavage with BuLi to give finally the ester 33.The tert-butyl esters 21 - 26 yield with KOtBu the cyclopropene esters 27 - 32.The trans-esters 21a - 26a react much faster than the cis-esters b.At C-3 unsubstituted chlorocyclopropane esters, e.g. 34, do not give stable cyclopropene esters even with lithium dialkylamides.Diazomethane adds to the esters 27 - 32 to give the pyrazolines 38 - 43, their isomers a and b being separable.With traces of base the bicyclic pyrazolines are cleaved to 1,4-dihydropyridazines 44 - 46.Cyclopropenes 27 - 30 react with thiophenolate to form the isomeric products 47 - 50; malonate adds to 28 and 31 to give 51, 52.With malononitrile via subsequent reactions the cyclopentadienes 55 - 57 are obtained.
- Norden, Wolfgang,Sander, Volker,Weyerstahl, Peter
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p. 3097 - 3111
(2007/10/02)
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