4313-57-9Relevant academic research and scientific papers
Rhodium(I)-Catalyzed Enantioselective C(sp3)—H Functionalization via Carbene-Induced Asymmetric Intermolecular C—H Insertion?
Liu, Bo,Xu, Ming-Hua
supporting information, p. 1911 - 1915 (2021/05/31)
Transition-metal-catalyzed C—H insertion of metal-carbene represents an excellent and powerful approach for C—H functionalization. However, despite remarkable advances in metal-carbene chemistry, transition metal catalysts that are capable of enantioselective intermolecular carbene C—H insertion are mainly constrained to dirhodium(II) and iridium(III)-based complexes. Herein, we disclose a new version of asymmetric carbene C—H insertion reaction with rhodium(I) catalyst. A highly enantioselective rhodium(I) complex-catalyzed C(sp3)—H functionalization of 1,4-cyclohexadienes with α-aryl-α-diazoacetates was successfully developed. By using chiral bicyclo[2.2.2]-octadiene as ligand, rhodium(I)-carbene-induced asymmetric intermolecular C—H insertion proceeds smoothly at room temperature, allowing access to a diverse variety of α-aryl-α-cyclohexadienyl acetates and gem-diaryl-containing acetates in good yields with good to excellent enantioselectivities (up to 99% ee). Furthermore, the synthetic utility of the reaction was highlighted by facile synthesis of a novel cannabinoid CB1 receptor ligand. This method may offer a new opportunity for the development of therapeutically exploitable cannabinoid receptor type ligands in medicinal chemistry.
Organocatalyzed Birch Reduction Driven by Visible Light
Cole, Justin P.,Chen, Dian-Feng,Kudisch, Max,Pearson, Ryan M.,Lim, Chern-Hooi,Miyake, Garret M.
supporting information, p. 13573 - 13581 (2020/09/03)
The Birch reduction is a powerful synthetic methodology that uses solvated electrons to convert inert arenes to 1,4-cyclohexadienes - valuable intermediates for building molecular complexity. Birch reductions traditionally employ alkali metals dissolved in ammonia to produce a solvated electron for the reduction of unactivated arenes such as benzene (Ered -3.42 V vs SCE). Photoredox catalysts have been gaining popularity in highly reducing applications, but none have been reported to demonstrate reduction potentials powerful enough to reduce benzene. Here, we introduce benzo[ghi]perylene imides as new organic photoredox catalysts for Birch reductions performed at ambient temperature and driven by visible light from commercially available LEDs. Using low catalyst loadings (1 mol percent), benzene and other functionalized arenes were selectively transformed to 1,4-cyclohexadienes in moderate to good yields in a completely metal-free reaction. Mechanistic studies support that this unprecedented visible-light-induced reactivity is enabled by the ability of the organic photoredox catalyst to harness the energy from two visible-light photons to affect a single, high-energy chemical transformation.
Substituent effects on the dehydration of arene hydrates in aqueous solution
O'Mahony, Michelle J.,More O'Ferrall, Rory A.,Boyd, Derek R.,Lam, Casey M.,O'Donoghue, Annmarie C.
supporting information, p. 989 - 996 (2014/01/06)
Rate constants have been determined by UV spectrophotometry at 25 °C for the acid-catalyzed dehydration of different types of monocyclic arene hydrates including those substituted at the 1-, 2- or 3-positions. General acid catalysis was not observed, and linear plots of pseudo-first-order rate constants for dehydration against hydronium concentration were obtained. A Hammett plot of the second-order rate constants for acid-catalyzed dehydration, kH (M-1s-1), of unsubstituted- (8a), 3-substituted (8b, 8c, 8d, 8e) and 1-substituted-benzene hydrates (14f and 14h) shows an excellent correlation with σ+ values and yields a large negative ρ-value of -6.5. The results are consistent with rate-determining formation of a benzenium ion in which direct mesomeric interaction with the substituent occurs, presumably permitted by the coplanar arrangement of the diene and carbocation centre in the intermediate. Data points for 2-substituted arene hydrates (13f, 13g, 13h, 13i) deviate negatively from the Hammett plot as direct mesomeric interaction with the substituent is not possible in the corresponding benzenium intermediates. Copyright 2013 John Wiley & Sons, Ltd. A large negative ρ-value of -6.5 is obtained in a correlation of rate constants for the acid-catalyzed dehydration of arene hydrates with σ+ values. Copyright
Reductions of benzene derivatives whose benzylic positions bear oxygen atoms under mild conditions
Menzek, Abdullah,Karakaya, Melek Goekmen,Kaya, Afsin Ahmet
experimental part, p. 2299 - 2307 (2009/03/12)
Reductions of compounds whose benzylic positions bear O-atoms, such as benzyl alcohol, dibenzyl ether, styrene oxide, benzaldehyde, acetophenone, and benzophenone, to the corresponding non-conjugated dienes were performed by using t-BuOH, Li, and gaseous
3-Methylenetricyclo[3.1.0.02,6]hexane, a tricyclic isomer of toluene: Synthesis and addition onto tetracyanoethylene
Hasselmann, Dieter,Loosen, Klaus,Fischer, Thomas,Kunz, Ulrike,Christl, Manfred
, p. 1374 - 1379 (2007/10/03)
A multistep ring-contraction route starting from tricyclo[4.1.0.02,7]heptan-3-one (1) resulted in a mixture of the title compound 7 and the homofulvene 8 in a ratio of 1:2.5. In a second synthesis, a 3.5:1 mixture of 7 and three additional hydrocarbons was obtained from 4-(phenylsulfanyl)tricyclo [3.1.0.02,6]hexan-3-one (9) in a two-step sequence. On being heated at 175 °C in solution, 7 rearranged to toluene. Treatment of 7 with tetracyanoethylene gave rise to a 1:5 mixture of the [2+2] cycloadduct 16 and the cyclopropadicyclopentene derivative 17. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.
Isomer differentiation by tri-osmium cluster complexation of substituted 1,3-cyclohexadienes
Ingham,Johnson,Sadler,Nairn
, p. 237 - 242 (2007/10/03)
A series of methyl- and dimethyl-substituted 1,3-cyclohexadienes have been prepared from their aromatic analogues via Birch reduction and subsequent isomerisation with Fe(CO)3 fragments. These ligands were reacted with [Os3(CO)10(CH3CN)2] to form tri-osmium decacarbonyl cluster compounds containing the η4-coordinated substituted 1,3-cyclohexadienes. The various isomers of the substituted dienes show a dramatic difference in their reactivity towards the tri-osmium cluster and it is likely that this is due to the steric interactions between the methyl substituents and the cluster framework, with this effect being more marked for the di-substituted ligands.
Composition of Mixtures of Hydrocarbons after BIRCH-Reduction of Substituted Benzenes and Acid Catalyzed Addition of Alcohols to Alkylsubstituted Cyclohexenes and Carbohexa-1,4-dienes
Beger, J.,Thomas, B.,Vogel, T.,Kirmse, K.,Lang, R.
, p. 481 - 488 (2007/10/02)
10 different benzene hydrocarbons 1, indane, tetraline, anisol and phenol are reduced by sodium in liquid ammonia in the presence of methanol to the BIRCH products 2.The product mixture compositions are determined through capillary GLC.On storage at +6 deg C some rearomatization of the 1,4-cyclohexadienes 2 occurs.Data of the 1H- and 13C-.n.m.r. spectra and also mass spectra of the BIRCH 1,4-dienes 2 are given.For comparison 4-alkoxycyclohexenes 4 and 1-alkoxy-1-methylcyclohexanes 8 are prepared and spectroscopically characterized.Acid-catalyzed addition of alcohols to the 1,4-cyclohexadienes systems is a slow process and gives the 4-alkoxy-4-alkylcyclohex-1-enes (4) only in moderate yields up to 30percent.Most of the products are dimers 5 and also oligomers 6 of the parent hydrocarbons 2.
A NEW FORM OF THE REDUCTION OF BENZENE AND ITS ALKYL-SUBSTITUTRD DERIVATIVES TO 1,4-DIHYDRO DERIVATIVES IN THE LITHIUM-ISOPROPYL ALCOHOL-ETHYLENEDIAMINE SYSTEM
Bazyl'chik, V. V.,Fedorov, P. I.,Odinokov, V. N.
, p. 1668 - 1670 (2007/10/02)
A new method, convenient and effective for preparative purposes, is proposed for the reduction of benzene, toluene, and o-cymene in the lithium-isopropyl alcohol-ethylenediamine system.It is based on reaction at 85-95 deg C with arene, alcohol, diamine, and metal in molar equivalent ratios of 1:4-6:0.25-0.5:2-3.
Molecules with Twist Bent Bonds. The Synthesis, Properties, and Reactions of trans-Bicyclohept-3-ene and Certain Methylated Derivatives
Gassman, Paul G.,Bonser, Steven M.,Mlinaric-Majerski, Kata
, p. 2652 - 2662 (2007/10/02)
trans-Bicyclohept-3-ene, 7-methyl-trans-bicyclohept-3-ene, and 7,7-dimethyl-trans-bicyclohept-3-ene have been synthesized.Comparison of their ease of oxidation with the ease of oxidation of the analogous cis-bicyclohept-3-enes has been made.Both the thermal and transition-metal complex promoted rearrangements of the trans-bicyclohept-3-enes have been studied.These systems thermally convert to the cis-bicyclohept-3-enes above 100 deg C and are catalytically rearranged at ambient temperature.Trans to cis isomerization alsooccurs at ambient temperature under photoinduced single electron transfer conditions.
Molecules with Twist Bent Bonds. A Comparison of the Thermal and Transition-Metal-Complex Promoted Rearrangements of Derivatives of trans-Bicyclohept-3-ene
Gassman, Paul G.,Mlinaric-Majerski, Kata
, p. 4803 - 4806 (2007/10/02)
7-Methyl-trans-bicyclohept-3-ene has been synthesized and the thermal and transition-metal-complex promoted rearrangements of trans-bicyclohept-3-ene, 7-methyl-trans-bicyclohept-3-ene, and 7,7-dimethyl-trans-bicyclohept-3-ene have been compared.
