- Rhodium-Catalyzed Regioselective and Chemoselective Deoxygenative Reduction of 1,3-Diketones
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The deoxygenative reduction of carbonyl compounds has been well established. However, most protocols developed typically require harsh reaction conditions or highly reactive/toxic reagents, and the deoxygenative reduction of 1,3-diketones is rarely explored despite their importance to synthetic chemistry and materials science. We describe here a rhodium-catalyzed regioselective and chemoselective deoxygenative reduction of 1,3-diketones under mild reaction conditions. This approach exhibited exceptionally high regioselectivity toward the aliphatic carbonyl reduction over aromatic carbonyl reduction. Moreover, the reaction showed good functional group tolerance and broad substrate scope as well as great potential in the late-stage modification and synthesis of natural products and pharmaceutical skeletons. Preliminary mechanistic studies and DFT calculations revealed that this reaction involved the deoxygenation of 1,3-diketone to α, β-unsaturated ketone and its subsequent 1,4-reduction. The noticeably lower energy barrier of the aliphatic C═O insertion into [Rh]-Bpin versus the aromatic C═O insertion was responsible for the high regioselectivity in this reduction.
- Guo, Xueying,Li, Ruolin,Lin, Zhenyang,Tao, Lei,Zhang, Bing,Zhao, Wanxiang
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p. 4640 - 4647
(2022/05/02)
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- KOtBu/DMSO Catalytic System for Isomerization of Allylic Alcohols to Ketones
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The isomerization of allylic alcohols is an important reaction because it can afford carbonyl compounds in an atom-economical manner. Although base-catalyzed methods are more desirable than those using transition-metal catalysts from both the economic and environmental points of view, these methods have several drawbacks, such as narrow substrate scope and high catalyst loading. This paper reports the development of an efficient KOtBu/DMSO catalytic system suitable for the isomerization of a broad range of allylic alcohols with good yields, to which previously reported systems could not be applied. This catalytic system was successfully applied to a tandem allylic isomerization/electrophilic trapping reaction, thereby highlighting its synthetic utility.
- Sai, Masahiro
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- Diels-Alder route to norbornane derived vicinal phosphane/borane frustrated Lewis pairs for the metal-free catalytic hydrogenation of α, β-unsaturated ketones
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The [4+2] cycloaddition reaction of the (dimesitylphosphino)cyclopentadienes 5a,b with N-phenylmaleimide gave the norbornene derivative 9. Its reduction with LiAlH4 produced the N-phenylpyrrolidino-annulated system 10. Treatment with Piers' bor
- W?lke, Christian,Daniliuc, Constantin G.,Kehr, Gerald,Erker, Gerhard
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supporting information
(2019/08/26)
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- Ni-Catalyzed β-Alkylation of Cyclopropanol-Derived Homoenolates
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Metal homoenolates are valuable synthetic intermediates which provide access to β-functionalized ketones. In this report, we disclose a Ni-catalyzed β-alkylation reaction of cyclopropanol-derived homoenolates using redox-active N-hydroxyphthalimide (NHPI) esters as the alkylating reagents. The reaction is compatible with 1°, 2°, and 3° NHPI esters. Mechanistic studies imply radical activation of the NHPI ester and 2e β-carbon elimination occurring on the cyclopropanol.
- Mills, L. Reginald,Zhou, Cuihan,Fung, Emily,Rousseaux, Sophie A. L.
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supporting information
p. 8805 - 8809
(2019/11/03)
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- Solvent-free direct α-alkylation of ketones by alcohols catalyzed by nickel supported on silica-alumina
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The α-alkylation of acetophenone with benzyl alcohol through borrowing hydrogen has been studied using nickel catalysis. Ni/SiO2-Al2O3 was found to be the best catalyst for this transformation and the corresponding alkylated acetophenone was obtained with 93% isolated yield. Following the objectives of clean and sustainable chemistry, the reaction occurs under solvent-free conditions and requires only a catalytic amount of base. This protocol was next applied to a wide range of ketones and alcohols and the desired products were isolated with 18-86% yields (26 examples). The recovery and recyclability of the nickel catalyst was also investigated and it was found to be active over 5 runs without significant loss of activity. Surprisingly, the active catalyst appears to include an amorphous nickel hydroxide layer.
- Charvieux, Aubin,Giorgi, Javier B.,Duguet, Nicolas,Métay, Estelle
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supporting information
p. 4210 - 4216
(2018/10/02)
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- Direct β-Alkylation of Ketones and Aldehydes via Pd-Catalyzed Redox Cascade
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We report a direct β-alkylation of ketones and aldehydes with simple alkyl bromides through a Pd-catalyzed redox-cascade strategy. The use of a Cu cocatalyst is important for improved efficiency. The reaction is redox-neutral, without the need for strong acids or bases. Both cyclic and acyclic ketones, as well as α-branched aldehydes, are suitable substrates for coupling with secondary and tertiary alkyl bromides. Concise formal synthesis of Zanapezil is achieved using this β-alkylation method.
- Wang, Chengpeng,Dong, Guangbin
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supporting information
p. 6057 - 6061
(2018/05/14)
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- Direct Decarboxylative-Decarbonylative Alkylation of α-Oxo Acids with Electrophilic Olefins via Visible-Light Photoredox Catalysis
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The decarbonylation of primary, secondary, and tertiary alkyl-substituted acyl radicals has been investigated through photoredox catalysis. A series of quaternary carbons and γ-ketoesters have been directly constructed by the photoredox 1,4-conjugate addi
- Chen, Jian-Qiang,Chang, Rui,Wei, Yun-Long,Mo, Jia-Nan,Wang, Zhu-Yin,Xu, Peng-Fei
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p. 253 - 259
(2018/02/19)
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- Iron-Catalyzed Radical Decarboxylative Oxyalkylation of Terminal Alkynes with Alkyl Peroxides
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An iron-catalyzed oxyalkylation of alkynes with alkyl peroxides as the alkylating reagents has been investigated. Alkyl peroxides are readily available from aliphatic acids and serve simultaneously as the alkylating reagents and internal oxidants. Primary, secondary, and tertiary alkyl groups of aliphatic acids were readily incorporated into C?C triple bonds and diverse α-alkylated ketones were synthesized. Mechanism studies revealed that this reaction involves highly reactive alkyl free radicals. A unique equilibrium between lauric acid and water catalyzed by the iron(III) catalyst was observed.
- Zhu, Xiaotao,Ye, Changqing,Li, Yajun,Bao, Hongli
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supporting information
p. 10254 - 10258
(2017/08/07)
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- Traceless chelation-controlled rhodium-catalyzed intermolecular alkene and alkyne hydroacylation
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A new functional-group tolerant, rhodium-catalyzed, sulfide-reduction process is combined with rhodium-catalyzed chelation-controlled hydroacylation reactions to give a traceless hydroacylation protocol. Aryl- and alkenyl aldehydes can be combined with both alkenes, alkynes and allenes to give traceless products in high yields. A preliminary mechanistic proposal is also presented. Traceless catalysis: The powerful combination of a chelation-controlled hydroacylation process and a new rhodium-catalyzed sulfide reduction gave the products of traceless hydroacylation. Aryl- and alkenyl aldehydes can be combined with alkenes, alkynes, and allenes to deliver traceless products in high yields (see scheme). Copyright
- Hooper, Joel F.,Young, Rowan D.,Weller, Andrew S.,Willis, Michael C.
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supporting information
p. 3125 - 3130
(2013/03/28)
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- Double hydroacylation reactions of acyclic and cyclic α,β- unsaturated aldehydes
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Double or quits? double hydroacylation reactions of acyclic and cyclic α,β-unsaturated aldehydes with olefins afford ketone and diketone products, respectively. Enantiomers are formed whose absolute configurations are controlled by the order of alkene addition.
- Cha, Kyung-Mi,Lee, Hyejeong,Park, Jung-Woo,Lee, Yura,Jo, Eun-Ae,Jun, Chul-Ho
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supporting information; experimental part
p. 1926 - 1930
(2011/10/17)
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- One-pot catalytic C-C double bond cleavage of α,β-enones aided by alkyl group-immobilized silica spheres
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Catalytic C-C double bond cleavage of α,β-enones with a 1-alkene and H2O was carried out in the presence of a (Ph3P)3RhCl catalyst, 2-amino-3-picoline, cyclohexylamine, benzoic acid, and alkyl group-immobilized silica spheres. Upon completion of the reaction, the corresponding ketones were obtained without needing a further hydrolysis step. In this reaction, alkyl group-immobilized silica spheres act as a water reservoir for hydrolysis of an intermediate ketimine and as a phase divider between the organic solution and H2O.
- Lee, Dong Hun,Jo, Eun-Ae,Park, Jung-Woo,Jun, Chul-Ho
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experimental part
p. 160 - 163
(2010/03/04)
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- Dual functionalities of hydrogen-bonding self-assembled catalysts in chelation-assisted hydroacylation
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(Figure Presented) A recyclable catalyst for chelation-assisted hydroacylation of an olefin with primary alcohol was developed using hydrogen-bonding self-assembled catalysts consisting of 2,6-diaminopyridine and barbiturate phosphine - rhodium(I) complex. Upon heating, these two catalysts act as homogeneous catalysts due to cleavage of the hydrogen bond, and these associate to form supramolecular assemblies via hydrogen bonding that can be separated from immiscible product phase upon cooling after the reaction.
- Park, Jung-Woo,Park, Ji-Hye,Jun, Chul-Ho
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p. 5598 - 5601
(2008/12/20)
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- Rh(I)-catalyzed solvent-free ortho-alkylation of aromatic imines under microwave irradiation
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The synthesis of ortho-alkylated ketones through a chelation-assisted Rh (I) catalyzed ortho-alkylation reaction of aromatic imines under microwave activated solvent-free conditions in monomode reactors was performed. These conditions have been also applied to hydroacylation and ortho-alkylation reactions with aldimines.
- Vo-Thanh, Giang,Lahrache, Hind,Loupy, André,Kim, In-Jung,Chang, Duck-Ho,Jun, Chul-Ho
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p. 5539 - 5543
(2007/10/03)
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- A New Solvent System for Recycling Catalysts for Chelation-Assisted Hydroacylation of Olefins with Primary Alcohols
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A new method to separate and reuse the catalyst system consisting of a rhodium complex and 2-aminopyridines for chelation-assisted hydroacylation was achieved using phenol and 4,4′-dipyridyl as the reaction medium, and 4-diphenylphosphinobenzoic acid as a ligand. Copyright
- Chang, Duck-Ho,Lee, Dae-Yon,Hong, Boo-Sun,Choi, Jun-Hack,Jun, Chul-Ho
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p. 424 - 425
(2007/10/03)
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- Remarkable Dependence of Diastereoselectivity on Anhydrous or Aqueous Solvent in the Indium Hydride Promoted Reductive Aldol Reaction of α,β-Unsaturated Ketones
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Dichloroindium hydride generated by the transmetallation between tributyltin hydride and indium trichloride predominantly reduced α,β-unsaturated ketones (enones) with 1,4-selectively even in the presence of aldehydes. Under anhydrous conditions, the successive aldol reaction between the resulting enolates and the remaining aldehydes proceeded with high anti-selectivity. The stereo-chemistry was dramatically reversed to be syn-selective by the use of water and methanol as an additive and solvent, respectively.
- Inoue, Katsuyuki,Ishida, Tatsuya,Shibata, Ikuya,Baba, Akio
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p. 283 - 287
(2007/10/03)
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- Solvent-free chelation-assisted hydroacylation of olefin by rhodium(I) catalyst under microwave irradiation
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A solvent-free protocol for the rhodium(I)-catalyzed intermolecular hydroacylation was achieved under microwave irradiation to furnish various ketones in high yields. The reactivity was improved by the addition of aniline as well as 2-amino-3-picoline and benzoic acid to induce a transimination, which facilitates the formation of intermediate aldimine. A comparison of the reactivity between the reaction performed under the conventional heating mode and the microwave irradiation using monomode reactor revealed an important specific microwave effect during the chelation-assisted hydroacylation. It is supposed that the observed specific microwave effect mainly originates from the formation of aldimine by condensation of aldehyde and amine, which leads to a development of charges in the transition state. This result confirms that the rate-determining step of the reaction is the initial condensation step rather than the subsequent hydroiminoacylation step.
- Loupy, Andre,Chatti, Saber,Delamare, Sarah,Lee, Dae-Yon,Chung, Jong-Hwa,Jun, Chul-Ho
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p. 1280 - 1285
(2007/10/03)
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- C-H and C-C bond activation of primary amines through dehydrogenation and transimination
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Matrix presented Dehydrogenation and subsequent transimination of primary amines offer a new pathway for C-H bond activation, ortho-alkylation, and C-C bond activation to afford a variety of ketones in the reaction of 1-alkene by a cocatalyt system of Rh(I) and 2-amino-3-picoline.
- Jun, Chul-Ho,Chung, Kwan-Yong,Hong, Jun-Bae
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p. 785 - 787
(2007/10/03)
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- Solvent-free chelation-assisted intermolecular hydroacylation: Effect of microwave irradiation in the synthesis of ketone from aldehyde and 1-alkene by Rh(I) complex
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As a green alternative to classical homogeneous catalyst in toluene in closed vessels, the intermolecular hydroacylation of 1-alkenes with aldehydes by Rh(I) complex (Wilkinson catalyst) can be realized efficiently under solvent-free conditions. When coupled to microwave activation, it results in a serious improvement when compared to classical conditions.
- Jun, Chul-Ho,Chung, Jong-Hwa,Lee, Dae-Yon,Loupy, André,Chatti, Saber
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p. 4803 - 4805
(2007/10/03)
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- Catalytic transformation of aldimine to ketimine by Wilkinson's complex through transimination
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(equation presented) The C-H bond activation in homogeneous catalysis is important for carbon skeleton construction through C-C bond formation. In this report, a new direct synthesis of ketimine from aldimine bearing no coordination site is demonstrated with high catalytic efficiency. Transimination is the major role for this catalytic reaction.
- Jun, Chul-Ho,Hong, Jun-Bae
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p. 887 - 889
(2008/02/10)
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- Direct conversion of benzyl alcohol to ketone by polymer-supported Rh catalyst
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Benzyl alcohol reacted with 1-alkene to give the corresponding ketone by in situ generated polystyrene-based rhodium catalyst. The catalytic activity of this polymer-supported rhodium catalyst has not been reduced after reusing it four times.
- Jun, Chul-Ho,Hong, Hye-Suk,Huh, Chan-Woo
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p. 8897 - 8900
(2007/10/03)
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- SRN1 Reactions of 7-Iodobicycloheptane, 1-Iodoadamantane, and Neopentyl Iodide with Carbanions Induced by FeBr2 in DMSO
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There was no reaction of 7-iodobicycloheptane (7-iodonorcarane, 1 ) exo-endo ratio of ca. 1) with acetophenone enolate ions 2 in DMSO at 25 deg C; however, with the addition of SmI2 or FeBr2 and under the same experimental conditions, the substitut
- Nazareno, Monica A.,Rossi, Roberto A.
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p. 1645 - 1649
(2007/10/03)
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- PHOTOSTIMULATED REACTIONS OF NEOPENTYL IODIDES WITH CARBANIONS IN DMSO BY THE SRN1 MECHANISM
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Neopentyl iodide, 1, reacted under photostimulation with several carbanionic nucleophiles in DMSO.With acetone enolate ion only reduction and dimerization occured, but good yields of substitution products have been obtained with acetophenone, 5, and anthrone, 9, anions as nucleophiles.Nitromethane anion, 7, does not react with 1 under irradiation, but good yields of the substitution products are obtained when the photostimulated reaction is carried out in the presence of acetone enolate ions (entrainment reaction).Inhibition experiments by p-dinitrobenzene and by the radical trap TEMPO, suggest that these reactions occur by the SRN1 mechanism of nucleophilic substitution.The photostimulated reaction of 1,3-diiodo-2,2-dimethylpropane, 15, with 5 gave the disubstitution product 17 and the reduced monosubstitution product 18.It has been found that the monosubstitution product 16 (in which iodine is retained) is not an intermediate of these reactions. 1-iodoadamantane, 12, is more reactive (ca. 4.9 times) than 1 in competitive experiments toward 5 and under photostimulation.
- Penenory, Alicia B.,Rossi, Roberto A.
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p. 605 - 610
(2007/10/03)
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- Reductive alkylation of electronegatively-substituted alkenes by alkylmercury halides
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Photolysis of alkylmercury halides in the presence of electronegatively-substituted 1-alkenes yields adduct radicals [RCH2CH(EWG).] that in some cases react with RHgX to form RCH2CH(HgX)(EWG), e.g., EWG = (EtO)2PO or PhSO2. When the EWG is carbonyl or cyano, the resonance stabilized adduct radicals fail to react with the alkyl mercury halide. In these cases photolysis with RHgCl/KI in Me2SO leads to the adduct mercurial via reaction of the adduct radicals with RHgI2-. The reactions of tertiary-enolyl adduct radicals are inefficient with RHgX/KI, and disproportionation of the adduct radicals is the major reaction pathway. For secondary- or tertiary-adduct radicals the reductive alkylation products are formed in excellent yield by reaction with RHgCl and silyl hydrides in Me2SO solution in a process postulated to involve RHgH as an intermediate. The relative reactivities of a number of α,β-unsaturated systems toward t-Bu. have been measured by competitive techniques. The results demonstrate a high reactivity of s-cis enones relative to the s-trans conformers.
- Russell, Glen A.,Shi, Bing Zhi,Jiang, Wan,Hu, Shuiesheng,Kim, Byeong H.,Baik, Woonphil
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p. 3952 - 3962
(2007/10/02)
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- Reductive alkylations involving 2°- and 3°-enolyl adduct radicals
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Reductive tert-butylation of electronegatively substituted alkenes is readily achieved in Me2SO by reaction with excess t-BuHgCl/Et3SiH. Reactivity studies indicate that towards t-Bu. s-cis enones are more reactive than the s-trans conformers.
- Russel,Shi
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p. 3841 - 3844
(2007/10/02)
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- Catalytic Enantioselective Conjugate Addition of Dialkylzinc Compounds to Chalcones
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Conjugate addition of diethylzinc to enones is catalyzed by a complex derived from Ni(acac)2 and C2-symmetric 2,2'-bipyridine 3 or chiral pyridines 5-12.The products are obtained with optical purities up to 89percent ee.A strong positive nonlin
- Bolm, Carsten,Ewald, Martina,Felder, Marcel
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p. 1205 - 1216
(2007/10/02)
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- Chelates as intermediates in nucleophilic additions to alkoxy ketones according to Cram's rule (cyclic model)
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Chelates have been considered intermediates in the often highly stereoselective reactions of α-alkoxy and similarly substituted ketones for over 30 years,10 but without mechanistic evidence. It is now shown, by stop-flow ("rapid injection") NMR kinetics,15 that the specific rates of reaction of ketones C6H5COCH(OR)CH3 with Me2Mg, where R = (i-Pr)3 ("TIPS"), t-BuPh2Si, t-BuMe2Si, Et3Si, Me3Si, and Me, parallel the diastereoselectivity of the reaction; i.e., the fastest reacting compound (R = Me) is the one which gives the highest proportion of the product predicted by Cram's chelate rule. The major product of the slowest reacting compound (R = TIPS) is not in accord with Cram's chelate rule, and this compound reacts at the same specific rate as the parent, C6H5COCH2CH3. This is in accord with earlier work indicating that TIPSO does not chelate. Compounds intermediate in the series react at intermediate rates and give the two diastereomeric products in proportions which can be calculated by assuming two competing reactions (cf. Figure 2): one proceeding via the chelated transition states giving the product predicted by the chelate rule and one not involving chelation which gives the same product composition as the R = TIPS compound. Direct steric effects on carbonyl reactivity due to the remote bulky silyloxy substituents have been excluded by the study of carbon analogues bearing similar bulky groups. Thus, the kinetic effect in the above series appears to be due to steric hindrance to chelation; hence, the parallel of specific rate and stereoselectivity demonstrates that high stereoselectivity is associated with strong chelation, as postulated by Cram and Kopecky in 1959.10.
- Chen, Xiangning,Hortelano, Edwin R.,Eliel, Ernest L.,Frye, Stephen V.
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p. 1778 - 1784
(2007/10/02)
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- Free-Radical Alkylations of Enones Involving Proton Transfers
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Radical chain alkylations of the SRN-type are described that involve the abstraction of a proton from intermediate adduct radicals to form radical anions capable of chain propagation by electron transfer to alkylmercury halides.Vinylic SRN
- Russell, Glen A.,Kim, Byeong Hyo,Kulkarni, Shekhar V.
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p. 3768 - 3770
(2007/10/02)
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- Activation of alkylidene-bridged heterobimetallic complexes toward electrophilic attack
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Treatment of alkylidene-bridged zirconium-aluminum species with HMPA renders the CAl bond of the alkylidene unit susceptible to electrophilic attack; in the absence of HMPA, the CZr bond is attacked.
- Clift, Susan M.,Schwartz, Jeffrey
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