- CuBr2-catalyzed ring opening/formylation reaction of cyclopropyl carbinols with DMF to synthesize formate esters
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An unprecedented protocol for the synthesis of formate esters has been developed by employing N,N-dimethylformamide (DMF) as both the source of CHO and solvent. This reaction undergoes ring opening of the cyclopropyl carbinols and in situ formation of homoallylic alcohols, which reacts with DMF to give the desired products. The substrate cyclopropyl carbinols with different groups participate smoothly in this process and the desired products are obtained in moderate to good yields.
- Zhuang, Daijiao,Gatera, Tharcisse,Yan, Rulong
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supporting information
(2020/10/19)
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- Direct Synthesis of Enones by Visible-Light-Promoted Oxygenation of Trisubstituted Olefins Using Molecular Oxygen
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A one-step synthesis of enones from olefins is described. The reaction was performed under visible-light irradiation in the presence of molecular oxygen and a photocatalyst. The reaction proceeded with various types of trisubstituted olefins to give enones in good yields with high regioselectivity. In particular, oxygen- and nitrogen-containing functional groups, heteroaromatic rings, and cyclopropanes were tolerated. Mechanistic studies and previous reports indicated that the active oxygen species generated in the reaction system is singlet oxygen.
- Harada, Shinji,Matsuda, Daiki,Morikawa, Takahiro,Nishida, Atsushi
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p. 1372 - 1377
(2020/10/02)
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- Oxygenation of styrenes catalyzed by N-doped carbon incarcerated cobalt nanoparticles
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NCI-Co catalyzed olefin oxygenation reactions were investigated. Among the metals examined, including noble metals, the reaction proceeded specifically on Co catalysts, and nitrogen dopant was crucial for the catalytic activity. The presence of NaBH4 as a hydride source, the corresponding alcohols were obtained in high yields. The substrates bearing a reductant-sensitive functional group were made tolerant by changing the reductant and using an additive, and furthermore, the corresponding ketones were accessed by changing reaction conditions. A preliminary examination of other SOMOphiles suggested that the heterogeneous catalyst systems have the potential to be applied to more general hydrofunctionalization of olefins to form various kinds of bonds. Several mechanistic studies suggested that the reaction proceeded in a heterogeneous manner and formed a radical intermediate on cobalt nanoparticle species.
- Yasukawa, Tomohiro,Kobayashi, Shū
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supporting information
p. 1980 - 1985
(2019/12/24)
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- Iridium-catalyzed asymmetric hydrogenation of 3,3-disubstituted allylic alcohols in ethereal solvents
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Ir-phosphinomethyl-oxazoline complexes have been identified as efficient, highly enantioselective catalysts for the asymmetric hydrogenation of 3,3-disubstituted allylic alcohols and related homoallylic alcohols. In contrast to other N,P ligand complexes, which require weakly coordinating solvents, such as dichloromethane, these catalysts perform well in more ecofriendly THF or 2-MeTHF. Their synthetic potential was demonstrated with the formal total synthesis of four bisabolane sesquiterpenes. Particularly high enantioselectivity values in the asymmetric hydrogenation of 3,3-disubstituted allylic alcohols and related homoallylic alcohols have been achieved with Ir-phosphinomethyloxazoline catalysts. In contrast to other N,P-ligand complexes, which require weakly coordinating solvents, such as CH 2Cl2, these catalysts perform well in more ecofriendly THF or 2-MeTHF (see scheme; CODa =a 1,5-cyclooctadiene). Copyright
- Bernasconi, Maurizio,Ramella, Vincenzo,Tosatti, Paolo,Pfaltz, Andreas
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supporting information
p. 2440 - 2444
(2014/03/21)
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- Selenium-catalyzed regioselective cyclization of unsaturated carboxylic acids using hypervalent iodine oxidants
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A new and convenient selenium-catalyzed regioselective cyclization of γ, δ-unsaturated carboxylic acids to the corresponding 3, 6-dihydro-2Hpyran- 2-ones is described. The cyclization products have been obtained in good to excellent yields using diphenyl diselenide as a catalyst and [bis(trifluoroacetoxy)iodo]benzene as a stoichiometric oxidant 2011 American Chemical Society.
- Singh, Fateh V.,Wirth, Thomas
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supporting information; experimental part
p. 6504 - 6507
(2012/02/02)
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- Synthesis of 1,2,4-trioxepanes and 1,2,4-trioxocanes via photooxygenation of homoallylic alcohols
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(Chemical Equation Presented) Homoallylic alcohols 4a-d, easily accessible in two steps from cyclopropyl methyl ketone, underwent a highly regioselective reaction with singlet oxygen to yield γ-hydroxyhydroperoxides 5a-d in 57-72% yield. Acid-catalyzed reaction of 5a-d with acetone, cyclopentanone, and cyclohexanone furnished 1,2,4-trioxepanes 8a-d, 9a-d, and 10a-d in good yields. Homoallylic alcohol 12 also underwent a highly regioselective photooxygenation to yield δ-hydroxyhydroperoxide 13 in 67% yield, which on reaction with acetone, cyclopentanone, and cyclohexanone, furnished 1,2,4-trioxocanes 16-18 in 41-55% yield.
- Singh, Chandan,Pandey, Shilpi,Saxena, Gunjan,Srivastava, Nisha,Sharma, Malvika
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p. 9057 - 9061
(2007/10/03)
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- Structural effects on the β-scission reaction of tertiary arylcarbinyloxyl radicals. The role of α-cyclopropyl and α-cyclobutyl groups
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A product and time-resolved kinetic study on the reactivity of tertiary arylcarbinyloxyl radicals bearing α-cyclopropyl and α-cyclobutyl groups has been carried out. Both the 1-cyclopropyl-1-phenylethoxyl (1 .) and α,α-dicyclopropylphenylmethoxyl (2.) radicals undergo β-scission to give cyclopropyl phenyl ketone as the major or exclusive product with rate constants higher than that measured for the cumyloxyl radical. It is proposed that in the transition state for β-scission of 1. and 2., formation of the C=O double bond is assisted by overlap with the C-C bonding orbitals of the cyclopropane ring. With tertiary arylcarbinyloxyl radicals bearing α-cyclobutyl groups such as the 1-cyclobutyl-1-phenylethoxyl (4.) and 1-cyclobutyl-1-phenylpropoxyl (5.) radicals, the fragmentation regioselectivity is essentially governed by the stability of the radical formed by β-scission. Accordingly, 4. undergoes exclusive C-cyclobutyl bond cleavage to give acetophenone, whereas with 5., competition between C-cyclobutyl and C-ethyl bond cleavage, leading to propiophenone and cyclobutylphenyl ketone in a 2:1 ratio, is observed.
- Bietti, Massimo,Gente, Giacomo,Salamone, Michela
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p. 6820 - 6826
(2007/10/03)
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- Reactivity and selectivity in the oxidation of styrene derivatives. V. studies on the oxidation of α-substituted styrenes
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The liquid phase oxidation of α-phenyl-1a, α-trimethylsilyloxy 1b, α-cyclopropyl-1c, α-trifluoromethyl-1d styrene, and styrene 1e with oxygen in chlorobenzene and cumene solution in the temperature range 55-125°C was investigated. The product yields were determined gaschromatographically. The epoxide selectivity increases up to 90°C with increasing temperature. The epoxides of 1a and 1c rearrange at higher temperatures, therefore their yield decreases. The relative chain propagation constants (kpC=C) were determined by competitive oxidations of cumene. WILEY-VCH Verlag GmbH, 1999.
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- Regioselective ring-opening of cyclopropyl ketones with organometallic reagents
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Regioselective ring-opening reaction of cyclopropyl ketones was conducted successfully, in which the reaction of cyclopropyl phenyl ketone with trimethylaluminum catalyzed by nickel acetyl-acetonate gave the ring-opening product in up to 76% yield.
- Ichiyanagi, Tsuyoshi,Kuniyama, Satoru,Shimizu, Makoto,Fujisawa, Tamotsu
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p. 1149 - 1150
(2007/10/03)
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- [(3-dimethylamino)propyl]dimethylaluminum: A convenient reagent for methylation and ethynylation of carbonyl compounds
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At 60-80°C the title compound methylates a variety of mono- and diketones. Aromatic aldehydes undergo simple methylation by the reagent only after initial treatment with an equivalent amount of AlCl3. Upon reaction of Me2Al(CH2)3NMe2 with terminal acetylenes the aluminum complex is converted into a carbonyl-alkynylation reagent.
- Baidossi, Wael,Rosenfeld, Ayelet,Wassermann, Brigit C.,Schutte, Stefan,Schumann, Herbert,Blum, Jochanan
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p. 1127 - 1130
(2007/10/03)
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- Bimolecular Formation of Radicals by H-Transfer, 7. - Bimolecular Formation of Radicals via H-Transfer with Catalysis by 7H-Benzanthracene
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The transfer hydrogenation of α-methylstyrene (2) by 9,10-dihydroanthracene (1) (DHA) with 7H-benzanthracene (8) as a catalyst proceeds already at 210-260 deg C.Isotopic labeling, ESR spectroscopy, radical clock experiments, solvents effects, and thermochemical calculations support the postulated stepwise radical mechanism induced by bimolecular formation of radicals. - Key Words: Molecule-induced radical formation, kinetics of / Catalysis / ESR spectroscopy / Radical clock / Isokinetic relationship
- Gerst, Matthias,Morgenthaler, Jens,Ruechardt, Christoph
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p. 691 - 696
(2007/10/02)
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- Samarium-Promoted Cyclopropanation of Allylic Alcohols
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The use of samarium/mercury amalgam in conjunction with diiodomethane or chloroiodomethane to generate samarium carbenoids for the efficient cyclopropanation of allylic alcohols is discussed.These hydroxyl-directed cyclopropanations occur under mild conditions and allow a wide range of substitution about both the olefin and the carbinol carbon in allylic alcohol substrates.High yields and high diastereoselectivities are observed for many substrates.
- Molander, Gary A.,Harring, Lori S.
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p. 3525 - 3532
(2007/10/02)
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- Organocuprate Reactions with Cyclopropanes. Evidence for Three Types of Mechanism
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Cyclopropane ring openings by organocuprates can be classified into three distinct classes.Mechanistically, the simplest openings are the direct nucleophilic displacements with enolate leaving groups.In order to be synthetically useful, these reactions usually require activation by two groups.Substrates that contain vicinal olefin and activating groups generally are opened by SN2'-like displacements.Finally, β-cyclopropyl-α,β-unsaturated ketones react by a mechanism intimately related to the conjugate addition reaction of α,β-unsaturated ketones.
- Bertz, Steven H.,Dabbagh, Gary,Cook, James M.,Honkan, Vidya
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p. 1739 - 1743
(2007/10/02)
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- REACTION OF 2,2-DISUBSTITUTED 1-(DIBROMOMETHYLENE)CYCLOPROPANES WITH METHYLLITHIUM
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In the reaction of 2,2-disubstituted 1-(dibromomethylene)cyclopropanes with methyllithium 4,4-disubstituted 1-buten-3-ynes and 2,2-disubstituted (1-bromoethylidene)cyclopropanes are formed in ratios which depend on the character of substitution in the cyclopropane ring.
- Kostikov, R. R.,Molchanov, A. P.,Nagi, Sh. M.
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p. 1291 - 1297
(2007/10/02)
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