64200-26-6Relevant academic research and scientific papers
Cyclopropane-alkene metathesis by gold(i)-catalyzed decarbenation of persistent cyclopropanes
Mato, Mauro,Martín-Torres, Inmaculada,Herlé, Bart,Echavarren, Antonio M.
, p. 4216 - 4219 (2019/05/06)
A gold(i)-catalyzed cyclopropane-alkene metathesis has been demonstrated with two new families of cyclopropane derivatives of naphthalene and phenanthrene (benzo-fused norcaradienes). In this process, metal carbene units are transferred from a persistent
Carboxylates as Nucleophiles in the Enantioselective Ring-Opening of Formylcyclopropanes under Iminium Ion Catalysis
Díaz, Estibaliz,Reyes, Efraim,Uria, Uxue,Carrillo, Luisa,Tejero, Tomas,Merino, Pedro,Vicario, Jose L.
supporting information, p. 8764 - 8768 (2018/05/30)
In this work, carboxylic acids, which are typically regarded as poor nucleophiles, are demonstrated to be competent reagents to promote the ring-opening of formylcyclopropanes after activation of the latter through iminium ion formation. Under optimized r
Spin-selective generation of triplet nitrenes: Olefin aziridination through visible-light photosensitization of azidoformates
Scholz, Spencer O.,Farney, Elliot P.,Kim, Sangyun,Bates, Desiree M.,Yoon, Tehshik P.
, p. 2239 - 2242 (2016/02/18)
Azidoformates are interesting potential nitrene precursors, but their direct photochemical activation can result in competitive formation of aziridination and allylic amination products. Herein, we show that visible-light-activated transition-metal comple
Mechanism of alcohol oxidation mediated by copper(II) and nitroxyl radicals
Ryland, Bradford L.,McCann, Scott D.,Brunold, Thomas C.,Stahl, Shannon S.
supporting information, p. 12166 - 12173 (2014/12/09)
2,2′-Bipyridine-ligated copper complexes, in combination with TEMPO (2,2,6,6-tetramethylpiperidine-N-oxyl), are highly effective catalysts for aerobic alcohol oxidation. Considerable uncertainty and debate exist over the mechanism of alcohol oxidation mediated by CuII and TEMPO. Here, we report experimental and density functional theory (DFT) computational studies that distinguish among numerous previously proposed mechanistic pathways. Oxidation of various classes of radical-probe substrates shows that long-lived radicals are not formed in the reaction. DFT computational studies support this conclusion. A bimolecular pathway involving hydrogen-atom-transfer from a CuII-alkoxide to a nitroxyl radical is higher in energy than hydrogen transfer from a CuII-alkoxide to a coordinated nitroxyl species. The data presented here reconcile a collection of diverse and seemingly contradictory experimental and computational data reported previously in the literature. The resulting Oppenauer-like reaction pathway further explains experimental trends in the relative reactivity of different classes of alcohols (benzylic versus aliphatic and primary versus secondary), as well as the different reactivity observed between TEMPO and bicyclic nitroxyls, such as ABNO (ABNO = 9-azabicyclo[3.3.1]nonane N-oxyl).
Stereoselective preparation of cyclopropylmagnesium reagents via a Br-Mg exchange using i-PrMgCl·LiCl in the presence of dioxane
Rauhut, Christian B.,Cervino, Christian,Krasovskiy, Arkady,Knochel, Paul
scheme or table, p. 67 - 70 (2009/05/28)
The reaction of various cyclopropyl bromides with i-PrMgCl·LiCl in THF-dioxane provides the corresponding magnesiated cyclopropane reagents with complete retention of configuration. Georg Thieme Verlag Stuttgart.
Evaluation of the selectivity of the epoxidation of cis- versus trans-alkenes by oxo[meso-tetrakis(2,6-dibromophenyl)porphinato]chromium(V). Dynamics, products, and van der Waals energies
He, Gong-Xin,Mei, Houng-Yau,Bruice, Thomas C.
, p. 5644 - 5650 (2007/10/02)
Studies of the reaction of oxo[meso-tetrakis(2,6-dibromophenyl)porphinato]chromium(V) [(Br8TPP)CrV(O)(X)] with a number of trans-alkenes have been carried out with the objective of clarifying the nature of the reported stereoselectivity of the epoxidation of cis-alkenes as compared to trans-alkenes. The alkenes employed were trans-p,p′-dimethoxystilbene, trans-stilbene, trans-β-methylstyrene, trans-p,p′-dicyanostilbene, trans-2-pentene, trans-5-decene, trans-2-hexenyl acetate, (E)-1,2-bis(trans-2,trans-3-diphenylcyclopropyl)ethene, and also (Z)-1,2-bis(trans-2,trans-3-diphenylcyclopropyl)ethene. The influence of electronic and steric factors in determining the second-order rate constants (k1) for the reactions of trans-alkenes with (Br8TPP)CrV(O)(X) were separated by use of the linear free-energy relationship of log k1 and the one-electron oxidation potentials (E1/2) established by the reaction of a series of cis-alkenes with (Br8TPP)CrV(O)(X). Quantification of the steric factors established that there is no appreciable steric retardation of the second-order rate constants for reaction of trans-p,p′-dimethoxystilbene, trans-β-methylstyrene, trans-2-pentene, trans-5-decene, and trans-2-hexenyl acetate with (Br8TPP)CrV(O)(X). Steric hindrance is quite marked with trans-stilbene, trans-p,p′-dicyanostilbene, and (E)-1,2-bis-(trons-2,trans-3-diphenylcyclopropyl)ethene. In comparison with trans-stilbene, the lack of a kinetic steric effect with trans-p,p′-dimethoxystilbene requires a change of mechanism. The standard free energy (ΔGo) for one-electron oxidation of trans-p,p′-dimethoxystilbene [(Br8TPP)CrV(O)(X) + >C=C8TPP)CrIV(O)(X) + >C+C?o values for trans-stilbene and cis-stilbene by 0.46 and 0.59 V, respectively. Thus, trans-p,p′-dimethoxystilbene but not trans-stilbene can undergo facile le- oxidation by (Br8TPP)CrV(O)(X). This can be shown to be allowed by comparison of ΔGo and ΔGa values. One-electron transfer can take place at significantly longer distances than can covalent bond formation. Computer docking experiments have defined the stereochemistry associated with the closest approach of minimal van der Waals repulsive forces in the reaction of trans- and cis-stilbene. For trans-stilbene the closest approach is at a distance of 3.88 A? from directly above the CrV(O) while for cis-stilbene lowest energy closest approach is at 2.81 A? with the C=C bond: (i) lined parallel to opposite meso carbons; and (ii) above the CrV(O) oxygen with an offset (α) from the perpendicular CrV-O bond of α = 24°. Product yields are in accord with assigned steric effects and the nature of the products and mode of formation are discussed.
The rate-limiting step in the one-electron oxidation of an alkene by oxo[meso-tetrakis(2,6-dibromophenyl)porphinato]-chromium(V) Is the formation of a charge-transfer complex
He, Gong-Xin,Arasasingham, Ramesh D.,Zhang, Guo-Hua,Bruice, Thomas C.
, p. 9828 - 9833 (2007/10/02)
We have propped, in previous studies, that the rate-limiting step in the oxidation of alkenes by hypervalent metal-oxo porphyrin spoecies is the formation of a charge-transfer (CT) complex. The CT complex then partitions, dependent upon the alkene and the
Nature of the Epoxidizing Species Generated by Reaction of Alkyl Hydroperoxides with Iron (III) Porphyrins. Oxidations of cis-Stilbene and (Z)-1,2-Bis(trans-2,trans-3-diphenylcyclopropyl)ethene byt-BuOOH in the Presence of [meso-Tetrakis(2,4,6-trimethylphenyl)porphinato]-, [meso-Tetrakis(2,6-dichlorophenyl)porphinato]-, and [meso-Tetrakis(2,6-dibromophenyl)porphinato]iron(III) Cloride
He, Gong-Xin,Bruice, Thomas C.
, p. 2747 - 2753 (2007/10/02)
The mechanism of the of the oxidation of alkenes by t-BuOOH in the of iron(III) tetraphenylporphyrins has been explored (CH2Cl2 solvent). The alkenes, cis-stilbene and (Z)-1,2,-bis(trans-2,trans-3diphenylcyclopropyl)ethene (1-Z), have been chosen because they serve as traps for radical intermediates. The substituted iron(III) tetraphenylporphyrin catalysts employed are [meso-tetrakis(2,4,6-trimethiytphenyl)porphinato]iron(III) chloride ((TMP)FeIII(Cl)), [meso-tetrakis(2,6-dichlorophenyl)porphinato]iron(III) chloride ((Cl8TPP)FeIII(Cl)), and [meso-tetrakis(2,6-dibromophenyl)porphinato]iron(III) chloride ((Br8TPP)FeIII(Cl)). In experiments, azobisisobutyronitrile (AIBN) was as a chain for the of the oxidation of the alkenes byt-BuOOH. Oxidation of cis-stilbene with iron(III) as as a (trace), a [1H NMR, MS(CI)] the structure PhCH[OO(t-Bu)]CH[O(t-Bu)]Ph. We the are of t-BuOO., rather than (+.Porph)FeIV(O), with cis-stilbene. Oxidation of 1-Z iron(III) porphyrins as catalysts provides A (1H NMR, MS(CI), FT-IR) as the major product . Other products are B (whose structure has not determined), which contains intact one of the two trans-2,trans-3-diphenylcyclopropane groups, trans-2,trans-3-diphenylcyclopropanecarboxaldehyde, and deoxybenzoin. In A, one cyclopropyl group has a undergone a cyclopropylcarbinyl to homoallylcarbinyl radical rearrangement (CPCRR) while the other has remained intact. The major product A arises from initial combination of t-BuOO. with 1-Z followed by CPCRR. Reaction sequences are suggested. The cis-epoxide of 1-Z (2-c) is in 3,2% yield when (Cl8T- PP)FeIII (Cl) is catalyst. A trace of 2-c is with (TMP)FeIII(a), but 2-c not be with (TMP)FeIII(Cl), but 2-c could not be detected with (Br8TPP)FeIII(Cl). The cis-epoxide 2-c most likely arises from the concerted reaction of 1-Z with the iron(IV)-oxo porphyrin π cation radical (+.Cl8TPP)FeIv(O)(Cl). The species (+.Cl8TPP)FeVI(O)(Cl) may be the direct of of reaction of (Cl8TPP)FeIII(Cl) with t-BuOOH in a mechanism that involves heterolytic O-O Alternatively, (+.Cl8TPP)FeIV(O)(Cl) may arise via (Cl8TPP)FeIII(Cl) + t-BuOOH → (Cl8TPP)FeIV(O) + t-BuO' followed by oxidation of (Cl8TPP)FeIV(O)FeIV by t-BuOOH (or other). It is pointed out that (Cl8TPP)FeIV(O), unlike (TMP)FeIV(O), accumulates in relatively high concentration and that t-BuOOH is present at 0.3 M.
Intermediates in the Epoxidation of Alkenes by Cytochrome P-450 Models. 2. Use of the trans-2,trans-3-Diphenylcyclopropyl Substituent in a Search for Radical Intermediates
Castellino, Angelo J.,Bruice, Thomas C.
, p. 7512 - 7519 (2007/10/02)
(Z)-1,2-Bis(trans-2,trans-3-diphenylcyclopropyl)ethene (1-Z) has been used to search for radical intermediates in the epoxidation reactions of cytochrome P-450 model systems.The studied systems used the following as catalysts: (meso-tetrakis(pentafluoroph
SYNTHESIS OF STEREOISOMERIC 1-HYDROXYMETHYL-2,3-DIALKYL(DIPHENYL)CYCLOPROPANES AND 1-FORMYL-2,3-DIALKYL(DIPHENYL)CYCLOPROPANES
Komendantov, M.I.,Panasyuk, T.B.
, p. 1308 - 1312 (2007/10/02)
Lithium aluminum hydride reduction of stereoisomeric 2,3-dipropyl(diphenyl)cyclopropanecarboxylic acid esters results in the formation of stereoisomeric 1-hydroxymethyl-2,3-dipropyl(diphenyl)cyclopropanes, which can be oxidized to the corresponding stereo
