- Platinum-Catalyzed α,β-Desaturation of Cyclic Ketones through Direct Metal–Enolate Formation
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The development of a platinum-catalyzed desaturation of cyclic ketones to their conjugated α,β-unsaturated counterparts is reported in this full article. A unique diene-platinum complex was identified to be an efficient catalyst, which enables direct metal-enolate formation. The reaction operates under mild conditions without using strong bases or acids. Good to excellent yields can be achieved for diverse and complex scaffolds. A wide range of functional groups, including those sensitive to acids, bases/nucleophiles, or palladium species, are tolerated, which represents a distinct feature from other known desaturation methods. Mechanistically, this platinum catalysis exhibits a fast and reversible α-deprotonation followed by a rate-determining β-hydrogen elimination process, which is different from the prior Pd-catalyzed desaturation method. Promising preliminary enantioselective desaturation using a chiral-diene-platinum complex has also been obtained.
- Chen, Ming,Dong, Guangbin
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supporting information
p. 7956 - 7961
(2021/03/01)
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- CeO2-Supported Pd(II)-on-Au Nanoparticle Catalyst for Aerobic Selective α,β-Desaturation of Carbonyl Compounds Applicable to Cyclohexanones
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Direct selective desaturation of carbonyl compounds to synthesize α,β-unsaturated carbonyl compounds represents an environmentally benign alternative to classical stepwise procedures. In this study, we designed an ideal CeO2-supported Pd(II)-on-Au nanoparticle catalyst (Pd/Au/CeO2) and successfully achieved heterogeneously catalyzed selective desaturation of cyclohexanones to cyclohexenones using O2 in air as the oxidant. Besides cyclohexenones, various bioactive enones can also be synthesized from the corresponding saturated ketones under open air conditions in the presence of Pd/Au/CeO2. Preliminary mechanistic studies revealed that α-C-H bond cleavage in the substrates is the turnover-limiting step of this desaturation reaction.
- Jin, Xiongjie,Mizuno, Noritaka,Takei, Daisuke,Yabe, Tomohiro,Yamaguchi, Kazuya,Yatabe, Takafumi
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p. 5057 - 5063
(2020/05/27)
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- Pyrazolo [4, 3 - h] aminoquin oxazolines and use thereof (by machine translation)
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The invention relates to a kind of the following formula I indicated by the pyrazolo [4, 3 - h] quinazoline derivatives and their use, the compounds inhibit the cell cycle protein dependent enzyme family (CDKs) in different subtype for example CDK4/6 activity, for the prevention and treatment of cancer, metabolic immune diseases, cardiovascular disease and the provision of new means of neurological diseases. (by machine translation)
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Paragraph 0130-0132
(2018/03/01)
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- Bismuth-substituted "sandwich" type polyoxometalate catalyst for activation of peroxide: Umpolung of the peroxo intermediate and change of chemoselectivity
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The epoxidation of alkenes with peroxides by WVI, MoVI, VV, and TiIV compounds is well established, and it is well accepted that the active intermediate peroxo species are electrophilic toward nucleophilic substrates. Polyoxotungstates, for example, those of the "sandwich" structure, [WZn(TM-L)2(ZnW9O34)2]q- in which TM = transition metal and L = H2O, have in the past been found to be excellent epoxidation catalysts. It has now been found that substituting the Lewis basic BiIII into the terminal position of the "sandwich" polyoxometalate structure to yield [Zn2BiIII2(ZnW9O34)2]14- leads to an apparent umpolung of the peroxo species and formation of a nucleophilic peroxo intermediate. There are two lines of evidence that support the formation of a reactive nucleophilic peroxo intermediate: (1) More electrophilic sulfoxides are more reactive than more nucleophilic sulfides, and (2) nonfunctionalized aliphatic alkenes and dienes showed ene type reactivity rather than epoxidation pointing toward "dark" formation of singlet oxygen from the nucleophilic intermediate peroxo species. Allylic alcohols reacted much faster than alkenes but showed chemoselectivity toward C-H bond activation of the alcohol and formation of aldehydes or ketones rather than epoxidation. This explained via alkoxide formation at the BiIII center followed by oxidative β-elimination.
- Amanchi, Srinivasa Rao,Khenkin, Alexander M.,Diskin-Posner, Yael,Neumann, Ronny
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p. 3336 - 3341
(2015/06/16)
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- Catalytic Enantioselective Nitroso Diels-Alder Reaction
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The nitroso Diels-Alder (NDA) reaction is an attractive strategy for the synthesis of 3,6-dihydro-1,2-oxazines and 1-amino-4-hydroxy-2-ene derivatives. Herein we report the Cu(I)-DTBM-Segphos catalyzed asymmetric intermolecular NDA reaction of variously substituted cyclic 1,3-dienes using highly reactive nitroso compounds derived from pyrimidine and pyridazine derivatives. In most of the cases studied, the cycloadducts were obtained in high yields (up to 99%) with very high regio-, diastereo-, and enantioselectivities (up to regioselectivity > 99:1, d.r. > 99:1, and >99% ee). As an application of this methodology, formal syntheses of conduramine A-1 and narciclasine were accomplished.
- Maji, Biplab,Yamamoto, Hisashi
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p. 15957 - 15963
(2016/01/09)
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- 2-Quinoxalinol diamine Cu(II) complex: Facilitating catalytic oxidation through dual mechanisms
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The Cu(II) complex 1, Cu(II)-6-N-3,5-di-tert-butylsalicylidene-6,7- quinoxalinol-diamine, has been developed to address problems with current methods of catalytic oxidation using tert-butyl hydroperoxide (TBHP). Complex 1 demonstrated an increased capability to utilize TBHP while limiting interference from free radical reactions and was demonstrated to be highly effective in the oxidations of a variety of olefins. the Partner Organisations 2014.
- Li, Yuancheng,Lee, Taebum,Weerasiri, Kushan,Wang, Tanyu,Buss, Emily E.,McKee, Michael L.,Gorden, Anne E. V.
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p. 13578 - 13583
(2014/11/08)
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- Synthesis of the 2-methylene analogue of the HRV 3C protease inhibitor thysanone (2-carbathysanone)
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The Human Rhinovirus (HRV) is the major aetiological agent for the common cold, for which only symptomatic treatment is available. HRV maturation and replication is entirely dependent on the activity of a virally encoded 3C protease that represents an attractive target for the development of therapeutics to treat the common cold. Herein we report the synthesis and biological evaluation of the 2-methylene analogue of the HRV 3C protease inhibitor (-)-thysanone (1) namely 2-carbathysanone (2), in an attempt to decipher the structural features in the natural product that are responsible for the 3C protease activity. 2-Carbathysanone (2) (and related analogues (±)-cis-23, (±)-cis-30, (±)-31) did not inhibit HRV 3C protease, indicating that the lactol functionality present in (-)-thysanone (1) is a critical structural feature required for inhibition.
- Schuenemann, Katrin,Furkert, Daniel P.,Choi, Eun Cho,Connelly, Stephen,Fraser, John D.,Sperry, Jonathan,Brimble, Margaret A.
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p. 905 - 912
(2014/02/14)
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- Old yellow enzyme-catalyzed dehydrogenation of saturated ketones
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Enzymes from extremophiles have always been of great interest for biotechnology because of their ruggedness against various stress factors. We have isolated, cloned, heterologously expressed and characterized a thermostable old yellow enzyme (OYE) from Geobacillus kaustophilus. In addition to the expected 'enone' reduction, GkOYE also catalyzes the reverse reaction, i.e., the desaturation of C-C bonds adjacent to a carbonyl to give the corresponding α,β-unsaturated ketone. The reaction proceeds at the expense of molecular oxygen without the need for a nicotinamide cofactor and represents an environmentally benign alternative to known chemical dehydrogenation methods.
- Schittmayer, Matthias,Glieder, Anton,Uhl, Michael K.,Winkler, Andreas,Zach, Simone,Schrittwieser, Joerg H.,Kroutil, Wolfgang,MacHeroux, Peter,Gruber, Karl,Kambourakis, Spiros,Rozzell, J. David,Winkler, Margit
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supporting information; experimental part
p. 268 - 274
(2011/04/22)
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- Total synthesis of (+)-nankakurines A and B and (±)-5-epi- nankakurine A
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The first total syntheses of the Lycopodium alkaloids (+)-nankakurine A (2), (+)-nankakurine B (3), and the originally purported structure 1 of nankakurine A were accomplished. The syntheses of 2 and 3 feature a demanding intramolecular azomethine imine cycloaddition as the key step for generating the octahydro-3,5-ethanoquinoline moiety and installing the correct relative configuration at the spiropiperidine ring juncture. The cyclization precursor was prepared from octahydronaphthalene ketone 50, which was assembled from enone (+)-9 and diene 48 by a cationic Diels-Alder reaction. The Diels-Alder reactants were synthesized from 5-hexyn-1-ol (16) and (+)-pulegone (49), respectively. The tetracyclic ring system of 1 was generated using an unprecedented nitrogen-terminated aza-Prins cyclization cascade. The enantioselective total syntheses of (+)-nankakurine A (2) and (+)-nankakurine B (3) establish the relative and absolute configuration of these alkaloids and are sufficiently concise that substantial quantities of 2 and 3 were prepared for biological studies. (+)-Nankakurine A and (+)-nankakurine B showed no effect on neurite outgrowth in rat hippocampal H-19 cells over a concentration range of 0.3-10 μM.
- Altman, Ryan A.,Nilsson, Bradley L.,Overman, Larry E.,Read De Alaniz, Javier,Rohde, Jason M.,Taupin, Veronique
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experimental part
p. 7519 - 7534
(2011/02/23)
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- METHOD FOR PRODUCING CARBONYL COMPOUND AN PRO-OXIDANT USED FOR PRODUCTION OF CARBONYL COMPOUND
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The invention provides a process for the preparation of a carbonyl compound in high efficiency by oxidizing an alcohol. The process for the preparation of a carbonyl compound of the present invention includes a step of oxidizing an alcohol in the presence of a compound of the formula (I) or a derivative or a salt thereof, and an oxidant, wherein R1 and R2 independently represent hydrogen, a halogen, a nitro or acidic group, or an alkyl or alkoxy group, each of which optionally has a substituent, or R1 and R2 combine the two carbon atoms to which they are boned to form an aromatic ring.
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Page/Page column 15-16
(2009/08/16)
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- 2-iodoxybenzenesulfonic acid as an extremely active catalyst for the selective oxidation of alcohols to aldehydes, ketones, carboxylic acids, and enones with oxone
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Electron-donating group-substituted 2-iodoxybenzoic acids (IBXs) such as5-Me-IBX (1g), 5-MeO-IBX (1h), and 4,5-Me2-IBX were superior to IBX 1a as catalysts for the oxidation of alcohols with Oxone (a trad emark of DuPont) under nonaqueous conditions, although Oxone was almost insoluble in most organic solvents. The catalytic oxidation proceeded more rapidly and cleanly in nitromethane. Furthermore, 2-iodoxybenzenesulfonic acid (IBS, 6a) was much more active than modified IBXs. Thus, we established a highly efficient and selective method for the oxidation of primary and secondary alcohols to carbonyl compounds such as aldehydes, carboxylic acids, and ketones with Oxone in nonaqueous nitromethane, acetonitrile, or ethyl acetate in the presence of 0.05-5molpercentof 6a, which was generated in situ from 2-iodobenzenesulfonic acid (7a) or its sodium salt. Cycloalkanones could be further oxidized to α,β- cycloalkenones or lactones by controlling the amounts of Oxone under the same conditions as above. When Oxone was used under nonaqueous conditions, Oxone wastes could be removed by simple filtration. Based on theoretical calculations, we considered that the relatively ionic character of the intramolecular hypervalent iodine-OSO2 bond of IBS might lower the twisting barrier of the alkoxyperiodinane intermediate 16.
- Uyanik, Muhammet,Akakura, Matsujiro,Ishihara, Kazuaki
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supporting information; experimental part
p. 251 - 262
(2009/06/28)
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- New insights into the mechanism of palladium-catalyzed allylic amination
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A comparative investigation into palladium-catalyzed allylic amination of unsubstituted aziridines and secondary amines has been carried out. The use of NH aziridines as nucleophiles favors formation of valuable branched products in the case of aliphatic allyl acetates. The regioselectivity of this reaction is opposite to that observed when other amines are used as nucleophiles. Our study provides evidence for the palladium-catalyzed isomerization of the branched (kinetic) product formed with common secondary amines into the thermodynamic (linear) product. In contrast, the branched allyl products obtained from unsubstituted aziridines do not undergo the isomerization process. Crossover experiments indicate that the isomerization of branched allylamines is bimolecular and is catalyzed by Pd0. The reaction has significant solvent effect, giving the highest branched-to-linear ratios in THF. This finding can be explained by invoking the intermediacy of σ-complexes, which is consistent with NMR data. The apparent stability of branched allyl aziridines towards palladium-catalyzed isomerization is attributed to a combination of factors that stem from a higher degree of s-character of the aziridine nitrogen compared to other amines. The reaction allows for regio- and enantioselective incorporation of aziridine rings into appropriately functionalized building blocks. The resulting methodology addresses an important issue of forming quaternary carbon centers next to nitrogen. The new insights into the mechanism of palladium-catalyzed allylic amination obtained in this study should facilitate synthesis of complex heterocycles, design of new ligands to control branched-to-linear ratio, as well as absolute stereochemistry of allylamines.
- Watson, Iain D. G.,Yudin, Andrei K.
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p. 17516 - 17529
(2007/10/03)
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- Oxidative Synthesis of α,β-Unsaturated Ketone from α-Iodo Ketone Using Peracid
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Oxidation of α-iodo ketone in CH2Cl2 using m-chloro-perbenzoic acid yields α,β-unsaturated ketone by β-H elimination in good yield. This reaction affords a new and convenient synthetic method for α,β-unsaturated ketone from α-iodo ketone.
- Horiuchi, C. Akira,Ji, Shun-Jun,Matsushita, Masatoshi,Chai, Wen
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p. 202 - 204
(2007/10/03)
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- Iodine(V) reagents in organic synthesis. Part 4. o-Iodoxybenzoic acid as a chemospecific tool for single electron transfer-based oxidation processes
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o-Iodoxybenzoic acid (IBX), a readily available hypervalent iodine(V) reagent, was found to be highly effective in carrying out oxidations adjacent to carbonyl functionalities (to form α, β-unsaturated carbonyl compounds) and at benzylic and related carbon centers (to form conjugated aromatic carbonyl systems). Mechanistic investigations led to the conclusion that these new reactions are initiated by single electron transfer (SET) from the substrate to IBX to form a radical cation which reacts further to give the final products. Fine-tuning of the reaction conditions allowed remarkably selective transformations within multifunctional substrates, elevating the status of this reagent to that of a highly useful and chemoselective oxidant.
- Nicolaou,Montagnon,Baran,Zhong
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p. 2245 - 2258
(2007/10/03)
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- Modulation of the reactivity profile of IBX by ligand complexation: Ambient temperature dehydrogenation of aldehydes and ketones to α,β-unsaturated carbonyl compounds
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The reactivity profile of IBX can be altered by complexation with various ligands (e. g. 1-4). A new complex, IBX·MPO, is a remarkably effective oxidant and allows the room-temperature dehydrogenation of carbonyl compounds, for example, the formation of cyclooctenones 6 and 7 from cyclooctanone 5. IBX = iodoxybenzoic acid; MPO = 4-methoxypyridine-N-oxide.
- Nicolaou,Montagnon, Tamsyn,Baran, Phil S.
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p. 993 - 996
(2007/10/03)
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- HIO3 and I2O5: Mild and selective alternative reagents to IBX for the dehydrogenation of aldehydes and ketones
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Economic and convenient: Iodic acid (1) and iodine pentoxide (2) form complexes 3 and 4, respectively, with DMSO when heated at 80°C for 1 h. The complexes are efficient agents for the dehydrogenation of ketones and aldehydes at 45-65°C. X-ray crystallographic analysis (see picture) shows that the iodine pentoxide. DMSO complex 4 self-assembles into a remarkable helix in the solid state.
- Nicolaou,Montagnon, Tamsyn,Baran, Phil S.
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p. 1386 - 1389
(2007/10/03)
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- Synthesis of optically active 5-(tert-butyldimethylsiloxy)-2- cyclohexenone and its 6-substituted derivatives as useful chiral building blocks for the synthesis of cyclohexane rings. Synthesis of carvone, penienone, and penihydrone
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Optically active 5-(tert-butyldimethylsiloxy)-2-cyclohexenone (1) and its 6-substituted derivatives 2a,b were synthesized from the readily available optically active ethyl 3-(tert-butyldimethylsiloxy)-5-hexenoate (4), where the Ti(II)-mediated intramolecular nucleophilic acyl substitution reaction and the FeCl3-mediated ring expansion reaction of a 1- hydroxybicyclo[3.1.0]hexane are the key reactions. The enone 1 reacted with higher-order cyanocuprates with excellent diastereoselectivity to afford the trans-addition products, trans-13, in excellent yields. The reaction of 1 with lower-order cyanocuprates proceeded with moderate to excellent syn- selectivity to afford cis-13. Treatment of trans- and cis-13 with DBU (1,8- diazabicyclo[5.4.0]undec-7-ene) or catalyst p-TSA (p-toluenesulfonic acid) resulted in a β-elimination reaction to furnish the corresponding optically active 5-substituted-2-cyclohexenones 14. The 1,4-addition reaction of 2a and 2b with organocy-anocuprates followed by treatment of the resulting 20 with DBU provided the 2,5-disubstituted-2-cyclohexenones 19 with excellent ee. The conversion of 14 into the 3,5-disubstituted-2-cyclohexenone 22 has also been carried out via 1,2-addition of alkyllithium onto the carbonyl group and the following oxidation with PCC (pyridinium chlorochromate). Similarly, the conversion of 19 into 2,3,5-trisubstituted-2-cyclohexenones 24 has been carried out. A highly efficient, first total synthesis of penienone 25 and penihydrone 26 has been accomplished. Thus, the 1,4-addition reaction of 1 with the (E,E)-1,3-heptadienyl cyanocuprate and consecutive trap of the resulting copper enolate with formaldehyde gave 28, which upon treatment with DBU or Pyr · HF yielded 25 and 26, respectively. An efficient synthesis of both enantiomers of carvone starting from (S)-20ab has been also accomplished.
- Hareau, Georges P.-J.,Koiwa, Masakazu,Hikichi, Shinichi,Sato, Fumie
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p. 3640 - 3650
(2007/10/03)
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- Synthesis of α,β-unsaturated ketone from α-iodo ketone using photoirradiation
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Irradiation of α-iodo ketone in hexane under a nitrogen atmosphere with a high-pressure mercury lamp (λ>300nm) at room temperature afforded the corresponding α,β-unsaturated ketones in good yield. This reaction affords a new, clean and convenient synthetic method for the α,β-unsaturated ketone.
- Ji, Shun-Jun,Takahashi, Eiji,Takahashi, T. Tomoyoshi,Horiuchi, C. Akira
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p. 9263 - 9266
(2007/10/03)
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- Mitsunobu Reaction of Unbiased Cyclic Allylic Alcohols
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The stereochemical inversion of unbiased allylic alcohols using triphenylphosphine, diethyl azodicarboxylate, and benzoic acid, commonly known as the Mitsunobu reaction, was studied in three different solvents with specific attention toward the product composition. The results generated for the Mitsunobu reaction of (R)-3-deuterio-2-cyclohexen-1-ol and the cis and trans isomers of 1-deuterio-5-methyl-2-cyclohexen-1-ol, 1-deuterio-5-tert-butyl-2-cyclohexen-1-ol, and optically active cis and trans 5-isopropyl-2-methyl-2-cyclohexen-1-ol all gave similar product distributions with respect to inversion and retention at the carbinol center as well-as syn and anti Sn2′ type addition when THF or benzene was used as the solvent (CH2Cl2 gave less selective product distributions). Interestingly, it was found that the quasi-equatorial and quasi-axial nature of the starting allylic alcohol does not appear to affect the product distribution for this reaction, nor does methyl substitution at the central carbon of the allylic alcohol. In all cases, significant amounts (8-28%) of non-SN2 type products were detected for these sterically unbiased allylic alcohols; only 72-77% of the product was from SN2 type reaction when sterically undemanding (R)-S-deuterio-2-cyclohexen-1-ol was subjected to Mitsunobu conditions.
- Shull, Brian K.,Sakai, Takashi,Nichols, Jeffrey B.,Koreeda, Masato
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p. 8294 - 8303
(2007/10/03)
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- Regio- and enantio-selective enolisations of cyclic ketones using chiral lithium amide bases
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Enolisations of 3-methylcyclohexanone 16, and of a trans-fused perhydroisoquinolone derivative 8, using several chiral lithium amide bases have been examined.In reactions involving a single enantiomer of the ketone 8, the use of a chiral base can result in enhancement or reversal of the normal regioselectivity of enolisation to give the enol silane derivatives 9 and 10, depending on the configuration of the base used.Similar matched and mismatched results are observed when (R)-3-methylcyclohexanone, (R)-16, is treated with either enantiomer of the chiral base 3.A new type of kinetic resolution, termed regiodivergent resolution, is observed when enolisation of the racemic ketones 8 or 16 is carried out using the chiral base 3.
- Bambridge, Kimberley,Clark, Barry P.,Simpkins, Nigel S.
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p. 2535 - 2542
(2007/10/02)
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- Chromium pillared clay catalysed allylic oxidation and oxidative deprotection of allyl ethers and amines : A simple and convenient procedure
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An efficient method for allylic oxidation of cyclic and acyclic alkenes to the corresponding α,β-unsaturated carbonyl compounds in good yields was described using catalytic amounts of chromiapillared montmorillonite and equimolar quantities of tert-butyl hydroperoxide. This is also a convenient method for selective oxidative deprotection of allyl ethers and amines using same system. Incidentally this is the first heterogeneous system for the allylic oxidation as well as oxidative deprotection.
- Choudary, Boyapati M.,Prasad, Annavajhula Durga,Swapna, Vinukonda,Valli, Velaga L. K.,Bhuma, Vedantam
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p. 953 - 962
(2007/10/02)
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- Reaction of organolithium reagents with η5-pentadienyl iron complexes: Formation of σ,η3-iron complexes
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Reaction of organolithium reagents with η5-pentadienyl iron complex 4 occurs at the C2/C4 position of the π-system, generating σ,η3-iron complexes 5. Air oxidation of these σ,η3-iron complexes generates cyclohexenones. Rea
- McDaniel, Keith F.,Kracker II, Larry R.,Thamburaj, Parinbam K.
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p. 2373 - 2376
(2007/10/02)
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- Methods for the introduction of a Phenylselenium Dichloride Group into he α-position of Carbonyl Compounds. Syntheses of Enones.
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Phenylselenium trichloride, PhSeCl3, direcly introduced, in fair yield, a PhSeCl2 group into the α-position of ketones with loss of HCl.To some extent, depending on the substrate, this reagent was also shown to act as a chlorinating agent toward ketones, yielding α-chloro ketones and α-phenylselenenyl ketones.The latter compounds were readily converted to selenium(IV) dichlorides by SO2Cl2 chlorination to significantly improve the overall yields of the selenetion process.The consecutive treatment of ketones with PhSeCl and SO2Cl2 could also be used for the introduction of a PhSeCl2 group, but this procedure was usually less efficient than the PhSeCl3-based one.Unsymmetrical ketones were selenated with poor regiocontrol.Aldehydes were primarily chlorinated by treatment with PhSeCl3, but consecutive treatment with PhSeCl3 and SO2Cl2 introduced a PhSeCl2 group into the α-position.Carboxylic acids and esters were ureactive toward PhSeCl3 and PhSeCl.PhSeCl3 underwent addition reactions with enones to introduce a PhSeCl2 group α or β to the carbonyl group, depending on the substrate.The carbonyl compounds substituted in the α-position with a PhSeCl2 group were easily converted to the corresponding α,β-unsaturated carbonyl compounds after hydrolysis/selenoxide elimination.Since the selenium(IV) intermediates involved were highly crustalline and easy to purify, the preparation of enones from symmetrical ketones via PhSeCl2 introduction/hydrolytic elimination was especially convenient to perform from the operational point of view.
- Engman Lars
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p. 4031 - 4037
(2007/10/02)
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- OXYDATION D'ALCENES CYCLIQUES PAR L'IODYLBENZENE CATALYSEE PAR L'ACETYLACETONATE DE VANADYLE
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Iodylbenzene with vanadyl acetylacetonate oxidizes cyclic alkenes, the experimental results accord with a free radical oxidation mechanism.
- Barret, R.,Pautet, F.,Daudon, M.,Mathian, B.
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p. 439 - 440
(2007/10/02)
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- Cytochalasin Support Studies. The C14-C19 Subunit of Cytochalasin C. Intramolecular 2 + 2 Photochemical Cycloaddition of Vinyl Sulfones
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An intramolecular 2? + 2? photochemical cycloaddition between a six-membered ring vinyl sulfone and a five-membered ring vinylogous ester is described.The process occurs with moderate regiospecificity, the direction being controlled by a cis-acetonide moiety on the six-membered ring.Attempts to fragment the β-alkoxy sulfone adduct to trigger a DeMayo ring expansion were unsuccessful.
- Musser, Arlene K.,Fuchs, P. L.
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p. 3121 - 3131
(2007/10/02)
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- The Conjugate Addition of a Silyl Group to Enones and its Removal with Copper(II) Bromide: A Protecting Group for the αβ-Unsaturation of αβ-Unsaturated Ketones
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Silyl-lithium reagents mixed with copper(I) salts react with enones, including esters and aldehydes, to give β-silyl carbonyl compounds in good yield.The β-silylketones can be used in synthesis without risk to the silyl group and the enone group can be restored by bromination-desilylbromination with copper(II) bromide.The principle is illustrated with syntheses of carvone and dihydrojasmone.
- Ager, David J.,Fleming, Ian,Patel, Shailesh K.
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p. 2520 - 2526
(2007/10/02)
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