- Selective hydrogenation of unsaturated carbonyls by Ni-Fe-based alloy catalysts
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Ni-Fe alloy catalysts prepared by a simple hydrothermal method and subsequent H2 treatment exhibited the greatest activity and selectivity for the hydrogenation of biomass-derived furfural to furfuryl alcohol among the examined second metals, such as Al, Ga, In, Co, and Ti. This work reveals that the alloying of Ni and Fe is a key factor in achieving highly selective hydrogenation of the CO moiety in unsaturated carbonyl substrates. We found that decreasing the temperature of H2 treatment (i.e. decreasing the crystallite size), e.g. Ni-Fe(2)HT-573 K (TOF = 952 h-1), increased the activity compared to that over Ni-Fe(2)HT-673 (TOF = 375 h-1) for furfural hydrogenation. This result suggests that a low-coordinated Ni-Fe alloy was imperative for the catalytic cycle. Moreover, the effect of the metal/support interface was critical; despite the high catalytic performance of Ni-Fe/TiO2, Ni-Fe/Al2O3, and Ni-Fe/CeO2, Ni-Fe supported on SiO2, taeniolite, and hydrotalcite catalysts were ineffective. Vibrational studies using FT-IR measurement confirmed that furfural was physically adsorbed on the surface of the Ni-Fe alloy catalyst via an η1(O) configuration. The synthetic scope of the Ni-Fe catalytic system was very broad; various types of unsaturated carbonyls, such as unsaturated aromatics, unconjugated aliphatics, and a large substituent, were selectively converted into the corresponding unsaturated alcohols.
- Putro, Wahyu S.,Kojima, Takashi,Hara, Takayoshi,Ichikuni, Nobuyuki,Shimazu, Shogo
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- Evaluation of norcarane as a probe for radicals in cytochome P450- and soluble methane monooxygenase-catalyzed hydroxylation reactions
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Norcarane was employed as a mechanistic probe in oxidations catalyzed by hepatic cytochome P450 enzymes and by the soluble methane monooxygenase (sMMO) enzyme from Methylococcus capsulatus (Bath). In all cases, the major oxidation products (>75%) were endo- and exo-2-norcaranol. Small amounts of 3-norcaranols, 2-norcaranone, and 3-norcaranone also formed. In addition, the rearrangement products (2-cyclohexenyl)methanol and 3-cycloheptenol were detected in the reactions, the former possibly arising from a radical intermediate and the latter ascribed to a cationic intermediate. The formation of the cation-derived rearrangement product is consistent with one or more reaction pathways and is in accord with the results of previous probe studies with the same enzymes. The appearance of the putative radical-derived rearrangement product is in conflict with other mechanistic probe results with the same enzymes. The unique implication of a discrete radical intermediate in hydroxylations of norcarane may be the consequence of a minor reaction pathway for the enzymes that is not manifest in reactions with other probes. Alternatively, it might reflect a previously unappreciated reactivity of norcaranyl cationic intermediates, which can convert to (2-cyclohexenyl)methanol. We conclude that generalizations regarding the intermediacy of radicals in P450 and sMMO enzyme-catalyzed hydroxylations based on the norcarane results should be considered hypothetical until the origin of the unanticipated results can be determined.
- Newcomb, Martin,Shen, Runnan,Lu, Yun,Coon, Minor J.,Hollenberg, Paul F.,Kopp, Daniel A.,Lippard, Stephen J.
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- Selective hydrogenation of furanic aldehydes using Ni nanoparticle catalysts capped with organic molecules
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Ni nanoparticles were synthesized by a colloidal method in the presence of organic surface-capping agents and used to catalyze the selective hydrogenation of unsaturated furanic aldehydes to furanic alcohols. The effects of the Ni nanoparticle size and surface organic layer were evaluated. Of the 3.7, 5.1, 6.8, and 10.4 nm Ni nanoparticles tested in selective furfural (FFR) hydrogenation to furfuryl alcohol (FFA), the 6.8 nm Ni nanoparticles exhibited the highest yield because access to the surface sites on the smaller and larger nanoparticles was blocked by the densely packed organic layer and by their agglomeration due to magnetic attraction, respectively. The capped Ni nanoparticles exhibited a high FFA yield of 96%, whereas significant over-hydrogenation was observed when uncapped calcined Ni/SiO2 catalysts with similarly sized Ni nanoparticles were employed. Steric hindrance of the Ni surface induced by the organic surface layer led to selective FFR hydrogenation to FFA. The capped Ni nanoparticles could be reused repeatedly without a significant loss in the FFA yield. They also exhibited high selectivity (>90%) in the hydrogenation of other unsaturated furanic aldehydes to their corresponding alcohols.
- Jeong, Hojin,Kim, Chanyeon,Yang, Sungeun,Lee, Hyunjoo
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- Stereochemistry of the Conversion of 1,3-Chloroalcohols in Alkaline Medium The Chemistry of 1,3-Bifunctional Systems. XXII
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The transformation of isomeric 1,3-Chloroalcohols 1-4, with cyclohexane skeleton, were studied in aqueous solution containing barium hydroxide.As regards the compounds with cis-configuration, 1 gives the oxetane 5 by intramolecular nucleophilic substitution, while 3 gives the unsatured alcohols 7 and 8 by elimination.In the case of the trans-isomers 2 and 4, fragmentation reactions occur in competition with elimination.The main reaction kinetic parameters of the transformations of the four compounds were determined.
- Bartok, Mihaly,Felfoeldi, Karoly,Bozoki-Bartok, Gizella
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- Stereodirecting Effect of a Substrate Methoxy Substituent on the Addition of Singlet Methylene to a Double Bond
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The stereodirecting effects of substrate methoxy, hydroxy, methylthio, and methyl substituents were examined in the addition of 1:CH2 to the double bonds of substrates 1a-d.The carbene, generated by photolysis of CH2N2, inserted into the C-H bonds of solvent and substrate, added to the substrate double bond to give products 2a-d, and attacked the oxygen or sulfur atom of substrates 1a-c to produce ylide intermediates which underwent 2,3-sigmatropic rearrangement to give products 3a-c.A preference for addition syn to the methoxy group of substrate 1a was observed when the reaction was run in pentane solution (syn-2a/anti-2a, 1.14 +/- 0.02), while a preference for formation of anti-2a was observed in diethyl ether solution (syn-2a/anti-2a, 0.92 +/- 0.03).A preference for 1:CH2 addition anti to the substrate substituent was observed for substrates 1b-d in both pentane and ether solution.The effect of the methoxy substituent was also examined in the addition of 1:CH2 to syn-7-methoxynorbornene (5b).Explanations for the substituent effects are offered based on both steric hindrance and interaction between 1:CH2 and the substituent, including formation and subsequent reaction of the ylide intermediates.
- Young, Terry A.,O'Rourke, Colleen,Gray, Nathan B.,Lewis, Brian D.,Dvorak, Curt A.,et al.
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- Desaturase reactions complicate the use of norcarane as a mechanistic probe. Unraveling the mixture of twenty-plus products formed in enzyme-catalyzed oxidations of norcarane
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(Chemical Equation Presented) Norcarane, bicyclo[4.1.0]heptane, has been widely used as a mechanistic probe in studies of oxidations catalyzed by several iron-containing enzymes. We report here that, in addition to oxygenated products, norcarane is also oxidized by iron-containing enzymes in desaturase reactions that give 2-norcarene and 3-norcarene. Furthermore, secondary products from further oxidation reactions of the norcarenes are produced in yields that are comparable to those of the minor products from oxidation of the norcarane. We studied oxidations catalyzed by a representative spectrum of iron-containing enzymes including four cytochrome P450 enzymes, CYP2B1, CYPΔ2B4, CYPΔ2E1, and CYPΔ2E1 T303A, and three diiron enzymes, soluble methane monooxygenase (sMMO) from Methylococcus capsulatus (Bath), toluene monooxygenase (ToMO) from Pseudomonas stutzeri OX1, and phenol hydroxylase (PH) from Pseudomonas stutzeri OX1. 2-Norcarene and 3-norcarene and their oxidation products were found in all reaction mixtures, accounting for up to half of the oxidation products in some cases. In total, more than 20 oxidation products were identified from the enzyme-catalyzed reactions of norcarane. The putative radical-derived product from the oxidation of norcarane, 3- hydroxymethylcyclohexene (21), and the putative cation-derived product from the oxidation of norcarane, cyclohept-3-enol (22), coelute with other oxidation products on low-polarity GC columns. The yields of product 21 found in this study are smaller than those previously reported for the same or similar enzymes in studies where the products from norcarene oxidations were ignored, and therefore, the limiting values for lifetimes of radical intermediates produced in the enzyme-catalyzed oxidation reactions are shorter than those previously reported.
- Newcomb, Martin,Chandrasena, R. Esala P.,Lansakara-P, Dharmika S. P.,Kim, Hye-Yeong,Lippard, Stephen J.,Beauvais, Laurance G.,Murray, Leslie J.,Izzo, Viviana,Hollenberg, Paul F.,Coon, Minor J.
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- Kinetic Resolution of Allyltriflamides through a Pd-Catalyzed C-H Functionalization with Allenes: Asymmetric Assembly of Tetrahydropyridines
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Enantioenriched, six-membered azacycles are essential structural motifs in many products of pharmaceutical or agrochemical interest. Here we report a simple and practical method for enantioselective assembly of tetrahydropyridines, which is paired to a ki
- González, José Manuel,Cendón, Borja,Mascare?as, José Luis,Gulías, Moisés
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- Distal Alkenyl C-H Functionalization via the Palladium/Norbornene Cooperative Catalysis
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A distal-selective alkenyl C-H arylation method is reported through a directed palladium/norbornene (Pd/NBE) cooperative catalysis. The key is to use an appropriate combination of the directing group and the NBE cocatalyst. A range of acyclic and cyclic c
- Dong, Guangbin,Fatuzzo, Nina,Wu, Zhao
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supporting information
p. 2715 - 2720
(2020/03/10)
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- Production of oxygen-containing alicyclic compounds (by machine translation)
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[Problem] to provide, in a one-step reaction synthesizes an alicyclic compound containing oxygen, high yield production of oxygen-containing compound is a cycloaliphatic. [Solution] one or more hydroxy or carbonyl group 2, or a hydroxyl group having the carbon number of 5 or more aliphatic carbonyl group 2 in accordance with one or more oxygen-containing compound, a basic catalyst is brought into contact with an oxygen-containing alicyclic compound by cyclodehydration reaction, oxygen-containing alicyclic compound. [Drawing] no (by machine translation)
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Paragraph 0035; 0038
(2020/04/24)
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- Gold-Catalyzed Stereoselective Synthesis of Bicyclic Lactams and Ketones from N-Tosylynamidomethyl-Tethered Cyclohexenes
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Six-membered ring 3-enynamides underwent cycloisomerization in the presence of a catalytic amount of a gold(I) complex delivering mainly 4-azatricyclo[4.3.1.03,10]dec-2-ene derivatives and dibenz[cd,f]indole derivatives as the minor products under mild reaction conditions. Upon exposure to air, most aryl-substituted azatricycles led to bicyclic γ-lactams, while the ortho-tolyl- or alkyl-substituted azatricycles provided the corresponding bicyclic γ-lactams after oxidation with osmium tetraoxide and N-methylmorpholine-N-oxide. Under acidic conditions, the ortho-tolyl- or alkyl-substituted azatricycles were further transformed into 5-N-tosylaminomethyl-tethered bicyclo[4.2.0]octan-7-ones. The gold(I)-catalyzed tandem cycloisomerization/oxidation reaction also provided a new route for the synthesis of bridged bicyclic δ-lactams from six-membered ring 4-enynamides. The mild reaction conditions allowed the synthesis of a range of bicyclic γ- and δ-lactams and N-tosylaminomethyl-tethered bicyclo[4.2.0]octan-7-ones with high diastereoselectivities.
- Zhong, Chang-Zhi,Tung, Po-Ting,Chao, Tsung-Han,Yeh, Ming-Chang P.
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p. 481 - 501
(2017/04/26)
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- Palladium- and ruthenium-catalyzed cycloisomerization of enynamides and enynhydrazides: A rapid approach to diverse azacyclic frameworks
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I want to ride my azacycle: The title reaction of enynamides affords a wide diversity of azacycles. The reactions are high-yielding, highly stereoselective, and proceed rapidly under mild reaction conditions. Equivalent transformations using enynhydrazides offer new routes to pyrazole and indazole scaffolds. Boc=tert-butoxycarbonyl, EWG=electron-withdrawing group, Ns=4-nitrobenzenesulfonyl, Ts=4-toluenesulfonyl. Copyright
- Walker, P. Ross,Campbell, Craig D.,Suleman, Abid,Carr, Greg,Anderson, Edward A.
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supporting information
p. 9139 - 9143
(2013/09/12)
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- Ammonium-directed olefinic epoxidation: Kinetic and mechanistic insights
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The ammonium-directed olefinic epoxidations of a range of differentially N-substituted cyclic allylic and homoallylic amines (derived from cyclopentene, cyclohexene, and cycloheptene) have been investigated, and the reaction kinetics have been analyzed. The results of these studies suggest that both the ring size and the identity of the substituents on nitrogen are important in determining both the overall rate and the stereochemical outcome of the epoxidation reaction. In general, secondary amines or tertiary amines with nonsterically demanding substituents on nitrogen are superior to tertiary amines with sterically demanding substituents on nitrogen in their ability to promote the oxidation reaction. Furthermore, in all cases examined, the ability of the (in situ formed) ammonium substituent to direct the stereochemical course of the epoxidation reaction is either comparable or superior to that of the analogous hydroxyl substituent. Much slower rates of ring-opening of the intermediate epoxides are observed in cyclopentene-derived and cycloheptene-derived allylic amines as compared with their cyclohexene-derived allylic and homoallylic amine counterparts, allowing for isolation of these intermediates in both of the former cases.
- Brennan, Meabh B.,Claridge, Timothy D.W.,Compton, Richard G.,Davies, Stephen G.,Fletcher, Ai M.,Henstridge, Martin C.,Hewings, David S.,Kurosawa, Wataru,Lee, James A.,Roberts, Paul M.,Schoonen, Anne K.,Thomson, James E.
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p. 7241 - 7261
(2012/11/07)
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- Parallel and competitive pathways for substrate desaturation, hydroxylation, and radical rearrangement by the non-heme diiron hydroxylase AlkB
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A purified and highly active form of the non-heme diiron hydroxylase AlkB was investigated using the diagnostic probe substrate norcarane. The reaction afforded C2 (26%) and C3 (43%) hydroxylation and desaturation products (31%). Initial C-H cleavage at C2 led to 7% C2 hydroxylation and 19% 3-hydroxymethylcyclohexene, a rearrangement product characteristic of a radical rearrangement pathway. A deuterated substrate analogue, 3,3,4,4-norcarane-d 4, afforded drastically reduced amounts of C3 alcohol (8%) and desaturation products (5%), while the radical rearranged alcohol was now the major product (65%). This change in product ratios indicates a large kinetic hydrogen isotope effect of ~20 for both the C-H hydroxylation at C3 and the desaturation pathway, with all of the desaturation originating via hydrogen abstraction at C3 and not C2. The data indicate that AlkB reacts with norcarane via initial C-H hydrogen abstraction from C2 or C3 and that the three pathways, C3 hydroxylation, C3 desaturation, and C2 hydroxylation/radical rearrangement, are parallel and competitive. Thus, the incipient radical at C3 either reacts with the iron-oxo center to form an alcohol or proceeds along the desaturation pathway via a second H-abstraction to afford both 2-norcarene and 3-norcarene. Subsequent reactions of these norcarenes lead to detectable amounts of hydroxylation products and toluene. By contrast, the 2-norcaranyl radical intermediate leads to C2 hydroxylation and the diagnostic radical rearrangement, but this radical apparently does not afford desaturation products. The results indicate that C-H hydroxylation and desaturation follow analogous stepwise reaction channels via carbon radicals that diverge at the product-forming step.
- Cooper, Harriet L. R.,Mishra, Girish,Huang, Xiongyi,Pender-Cudlip, Marilla,Austin, Rachel N.,Shanklin, John,Groves, John T.
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p. 20365 - 20375
(2013/02/25)
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- SnCl2/KI-mediated allylation reactions of formaldehyde in water
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An efficient procedure for SnCl2/KI-mediated allylation reactions of formaldehyde with a variety of allylic bromides in aqueous solution is reported. Under conditions developed in this effort, various homoallylic alcohols and 2-halohomoallylic alcohols are produced in good to excellent yields. Georg Thieme Verlag Stuttgart New York.
- Lin, Mei-Huey,Lin, Long-Zhi,Chuang, Tsung-Hsun
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supporting information; experimental part
p. 1871 - 1874
(2011/09/16)
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- Ammonium-directed oxidation of cyclic allylic and homoallylic amines
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(Chemical Equation Presented) The ammonium-directed olefinic oxidation of a range of cyclic allylic and homoallylic amines has been investigated. Functionalization of a range of allylic 3-(N,N-dibenzylamino)cycloalk-1-enes with m-CPBA in the presence of Cl3CCO2H gives exclusively the corresponding syn-epoxide for the 5-membered ring (>99:1 dr), the anti-epoxide for the 8-membered ring (>99:1 dr), and predominantly the anti-epoxide for the 7-membered ring (94:6 dr). Oxidation of the homoallylic amines 3-(Nbenzylamino) methylcyclohex-1-ene and 3-(N,N-dibenzylamino)methylcyclohex-1-ene gave, in both cases, the correspondingN-protected 1,2-anti-2,3-syn-3-aminomethylcyclohexane- 1,2-diol with high levels of diastereoselectivity (g90:10 dr). The versatile synthetic intermediates resulting from these oxidation reactions are readily transformed into a range of amino diols.
- Bond, Christopher W.,Cresswell, Alexander J.,Davies, Stephen G.,Fletcher, Ai M.,Kurosawa, Wataru,Lee, James A.,Roberts, Paul M.,Russell, Angela J.,Smith, Andrew D.,Thomson, James E.
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supporting information; experimental part
p. 6735 - 6748
(2009/12/31)
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- Cage escape competes with geminate recombination during alkane hydroxylation by the diiron oxygenase AlkB
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(Chemical Presented) AlkBstops the radical clock: Three structurally analogous radical-clock substrates with a large span in their rearrangement rates are hydroxylated by AlkB to afford similar amounts of rearranged (2) and unrearranged products (1). Such a result is in accord with radical rebound competing with cage escape of the geminate substrate radical. The results show that radical clocks can measure both the radical lifetime and the kinetics of cage escape.
- Austin, Rachel N.,Luddy, Kate,Erickson, Karla,Pender-Cudlip, Marilla,Bertrand, Erin,Deng, Dayi,Buzdygon, Ryan S.,Van Beilen, Jan B.,Groves, John T.
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supporting information; experimental part
p. 5232 - 5234
(2009/04/04)
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- Radical intermediates in monooxygenase reactions of Rieske dioxygenases
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Rieske dioxygenases catalyze the cis-dihydroxylation of a wide range of aromatic compounds to initiate their biodegradation. The archetypal Rieske dioxygenase naphthalene 1,2-dioxygenase (NDOS) catalyzes dioxygenation of naphthalene to form (+)-cis-(1R,2S
- Chakrabarty, Sarmistha,Austin, Rachel N.,Deng, Dayi,Groves, John T.,Lipscomb, John D.
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p. 3514 - 3515
(2007/10/03)
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- Stereoselective cyclization reactions of IBX-generated alkoxyamidyl radicals
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In this paper, a method for the generation of alkoxyamidyl radicals is presented. These N-centered radicals can efficiently be formed starting from the corresponding acylated alkoxyamines using IBX as an oxidant. Stereoselective 5-exo and 6-exo reactions with these N-heteroatom-centered radicals leading to isoxazolidines and [1,2]oxazinanes are discussed. The N-O bond in the heterocycles can readily be cleaved with SmI2 to provide N-acylated 1,3-amino alcohols.
- Janza, Birgit,Studer, Armido
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p. 6991 - 6994
(2007/10/03)
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- Use of cyclic allylic bromides in the zinc-mediated aqueous Barbier-Grignard reaction
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The zinc-mediated aqueous Barbier-Grignard reaction of cyclic allylic bromide substrates with various aldehydes and ketones to afford homoallylic alcohols was investigated. Aromatic aldehydes and ketones afforded adducts in good yields (66-90%) and with good diastereoselectivities. Non-aromatic aldehydes also reacted well under these conditions, but only poor yields were obtained with non-aromatic ketones. Regioselectivity was high when some substituted cyclic allylic bromides were investigated.
- Breton, Gary W.,Shugart, John H.,Hughey, Christine A.,Conrad, Brian P.,Perala, Suzanne M.
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p. 655 - 662
(2007/10/03)
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- 6-Methyltetracyclo[4.2.0.01,7.05,7]octane - A bridged [3.3.3]fenestrane
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The reaction of 1-bromo-2-chloromethyl-7-methyltricyclo[4.1.0.02,7]heptane with methyllithium leads to either 2-methyl-3-methylenetricyclo[4.1.0.02,7]heptane or 7-bromo-1,7-dimethyl-2-methylenebicyclo[4.1.0]heptane depending on the m
- Alber, Frank,Szeimies, Guenter
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p. 4093 - 4096
(2007/10/02)
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- Regiochemical Control of the Ring Opening of 1,2-Epoxides by Means of Chelating Processes. 4. Synthesis and Reactions of the cis- and trans-Oxides Derived from 3-cyclohexene
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The synthesis and nucleophilic addition reactions of diastereoisomeric title epoxides cis-7 and trans-8 were studied.While the ring-opening reactions of trans epoxide 8 are rationalized by means of steric, stereoelectronic, and conformational arguments, the analogous reactions of cis epoxide 7 indicate the ability of this isomer to react through chelated intermediates when metal salt catalyst is used.In 7 chelation reaction conditions led to a significant increase of nucleophilic attack on the C-1 oxirane carbon; the lack of reversal of the regiochemistry of the ring opening on passing from nonchelating to chelating reaction conditions suggests that cis epoxide 7 reacts through its more stable conformation in both of the two different operating conditions.
- Chini, Marco,Crotti, Paolo,Flippin, Lee A.,Gardelli, Cristina,Macchia, Franco
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p. 1713 - 1718
(2007/10/02)
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- Homolytic Displacement at Saturated Carbon: Part 5. Synthesis of Cyclopropylmethyl, Bicyclohex-2-yl, Bicyclohept-2-yl and Cyclohexanespirocycloprop-2-yl Sulphones from the Corresponding But-3-enylcobaloximes
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But-3-enylcobaloxime reacts with arenesulphonyl chlorides under thermal and photochemical conditions to give cyclopropylmethyl sulphones.The yields depend upon the reaction conditions used.Similar reactions of cyclopent-2-enylmethylcobaloxime and cyclohex-2-enylmethylcobaloximes under photochemical conditions form a mixture of cis and trans isomers of bicyclohex-2-yl and bicyclohept-2-yl sulphones in (50:50) and (70:30) isomeric ratios respectively.However, cyclohex-3-enylcobaloximes form only the trans-bicyclohex-2-yl sulphone.Exclusive formation of cycloalkanespirocycloprop-2-yl sulphones is observed in the reactions of 2-(cyclo alk-1-enyl)ethylcobaloximes with arenesulphonyl chlorides.The reactions are free radical in nature and are believed to take place by a chain mechanism.In the key step a homolytic attack of the RSO2 radical at the terminal (δ) carbon of the butenyl ligand leads to the cyclized product.The exact nature of the ring closure step is uncertain, as both concerted and stepwise mechanisms are possible.
- Gupta, B. Dass,Das, Indira,Dixit, Vandana
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p. 2409 - 2446
(2007/10/02)
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- SYNTHESIS OF OXACYCLIC CARBOXYLIC ESTERS THROUGH RING CLOSURE OF Α-ALKOXY ESTER FREE RADICALS
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Cyclizations of 1-methoxycarbonyl-2-oxa-5-hexenyl (and related) radical intermediates, generated from phenylthio precursors, proceed in good yields and mainly lead to substituted 2-tetrahydrofurancarboxylic esters.
- Lolkema, Lucie D. M.,Hiemstra, Henk,Ghouch, Al Ayachi Al,Speckamp, W. Nico
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p. 1491 - 1494
(2007/10/02)
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- Synthesis with organoboranes V. Hydroxymethylation and formylation of cycloalkenes via allylic organopotassium and organoboron compounds
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Allylic hydroxymethylation of cyclohexene and cyclooctene was achieved by metallation with trimethylsilylmethylpotassium followed by the reaction with formaldehyde. 1-Methylcycloalkenes were transformed into 2-methylenecycloalkane-1-methanols by the reaction of formaldehyde with allylic diethylboranes derived from these olefins via metallation-transmetallation.Conjugated cycloalkenecarboxaldehydes were obtained by oxidation of the hydroxymethylation products.
- Zaidlewicz, Marek
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p. 103 - 107
(2007/10/02)
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- Hydrated ?-bonded organometallic cations in organic synthesis. I. Allyl-, crotyl-, 1-methylallyl-, cyclohex-2-enyl-, and cinnamyl-stannation of carbonyl compounds in water
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Homoallylic alcohols can be prepared in water by allyl-, crotyl-, 1-methylallyl-, cyclohex-2-enyl-, or cinnamyl-stannation of such carbonyl compounds as aldehydes, dialdehydes, and ketones, as well as acetals.The procedure is based on: Bu2RSnCl + R'COR" + (1/2)H2O -> R(HO)CR'R" + (1/2)(Bu2SnCl)2O where R = allyl, crotyl, 1-methylallyl, cyclohex-2-enyl, or cinnamyl group, R' = H or alkyl group, R" R'= alkyl group.In most cases, the reaction products are obtained rapidly in high yields (80-100percent).Hydrated organometallic cations Bu2RSn+(aq) are partly involved.These results, together with those already published on 2-propynyl-and allenyl-stannation, indicate the value of this procedure.
- Furlani, Donatella,Marton, Daniele,Tagliavini, Giuseppe,Zordan, Michele
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p. 345 - 356
(2007/10/02)
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- Cycloalkylmethyl Radicals. Part 4. Electron Spin Resonance Study of Conformational Equilibria in Cyclohexenylmethyl and 4-Alkylcyclohexenylmethyl Radicals
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For cyclohex-2-enylmethyl and 4-alkoxycyclohex-2-enylmethyl radicals the quasi-axial and the quasi-equatorial conformers can both be observed by e.s.r. spectroscopy.Similary, the axial and equatorial conformers of cyclohex-3-enylmethyl radical can be distinguished by e.s.r. spectroscopy.The conformational free-energy difference of the CH2. group in the 2-position, -ΔGdeg300, was found to be 0.17 +/- 0.03 kcal mol-1 and in the 3-position -ΔGdeg300=0.0 +/- 0.1 kcal mol-1.The Arrhenius parameters for inversion of the half-chair conformation of cyclohex-2-enylmethyl radical were determined by lineshape analysis of the exchange-broadened spectra and found to be: log(kf/s-1)=12.3 - (5.7 kcal mol-1)/2.3RT and log(kb/s-1)=12.0 - (5.5 kcal mol-1)/2.3RT.The barrier to rotation about the C.α-Cβ bond in a cyclohexenylmethyl radicals is much less than the barrier in a cyclohexylmethyl radical because the former radical has only one syn-axial hydrogen on C(5) to impede the rotation whereas the latter radical has two syn-axial hydrogens on C(3) and C(5).
- Walton, John C.
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p. 1641 - 1646
(2007/10/02)
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- Photochemical Hydroxymethylation of Alicyclic and Aliphatic Alkenes Induced by a EuIII/EuII Photoredox System in Methanol
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The photoirradiation of a methanol solution of EuCl3 and alkenes such as cyclohexene, cyclooctene, cyclododecene, and tetramethylene afforded (hydroxymethyl)alkane.The dihydro dimer of alkene,hydrogen, and ethylene glycol are also formed.Reactions proceed via a radical mechanism induced by hydrogen atoms and hydroxymethyl radicals, which are produced by a photoredoc reaction of EuIII/EuII in methanol.
- Ishida, Akito,Yamashita, Shinya,Toki, Susumu,Takamuku, Setsuo
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p. 1195 - 1200
(2007/10/02)
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- HOMOLYTIC DISPLACEMENT AT CARBON. X. TOLUENESULPHONYL IODIDE AS A SOURCE OF TOLUENESULPHONYL RADICALS FOR THE FORMATION OF ALLYL-, BENZYL-, CYCLOPROPYLCARBINYL-, SPIROCYCLOPROPYLCYCLOALKYL-, BICYCLOALKYL-, AND BICYCLOALKYL-4-TOLYLSULPHONES FROM ORGANOCOBALOXIMES
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4-Toluenesulphonyl iodide reacts thermally at alkylsulphone.Spiro- and bicyclo-alkyl compounds are also formed with other free radical precursors.The reactions are believed to take place through a chain mechanism in which cobaloxime(II), present adventitiously or formed by partial homolysis of the substrate, abstracts iodine from the toluenesulphonyl iodide to give the toluenesulphonyl radical, which attacks the organic ligand of the cobaloxime, preferably at the terminal olefinic carbon, thereby displacing cobaloxime(II) and giving the observed organic product.
- Ashcroft, Martyn R.,Bougeard, Peter,Bury, Adrian,Cooksey, Christopher J.,Johnson, Michael D.
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p. 403 - 416
(2007/10/02)
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- DIMETHYLALUMINUM CHLORIDE CATALYZED ENE REACTIONS OF ALDEHYDES.
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Dimethylaluminum chloride, which is a mild Lewis acid and a proton scavenger, catalyzes the ene reactions of aliphatic and aromatic aldehydes with alkenes containing a disubstituted vinylic carbon. Proton-initiated rearrangements do not occur, since the alcohol-Lewis acid complex formed in the ene reaction reacts rapidly to give methane and a nonacidic aluminum alkoxide. Formaldehyde and excess Me//2AlCl give good yields of ene adducts with all types of alkenes. With 1 equiv of Me//2AlCl, formaldehyde and mono- and 1,2-disubstituted alkenes give gamma -chloro alcohols resulting from cis addition of chlorine and hydroxymethyl groups to the double bond. This work is pertinent to the synthesis of alcohols.
- Snider,Rodini,Kirk,Cordova
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p. 555 - 563
(2007/10/02)
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- SYNTHESIS OF β-(2,3-EPOXYCYCLOHEXYL)ALANINE AND ALANYL-β-(2,3-EPOXYCYCLOHEXYL)ALANINE
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Syntheses of new analog of antibiotic tetaine alanyl-β-(2,3-epoxycyclohexyl)alanine and its C-terminal amino acid are described.
- Smulkowski, Maciej,Dzieduszycka, Maria,Borowski, Edward
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p. 699 - 704
(2007/10/02)
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- Diaklylaluminum chloride catalyzed ene reactions of aldehydes. Synthesis of ipsenol
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Dimethylaluminum chloride which is a mild Lewis acid and a proton scavenger, catalyzes the ene reactions of aliphatic and aromatic aldehydes. Proton initiated rearrangements do not occur, since the alcohol-Lewis acid complex formed in the ene reaction rapidly to give methane and a non-acidic aluminum alkoxide.
- Snider, Barry B.,Rodini, David J.
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p. 1815 - 1818
(2007/10/02)
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