- Development and Mechanistic Investigations of Enantioselective Pd-Catalyzed Intermolecular Hydroaminations of Internal Dienes
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We report the development of highly enantio- and regioselective Pd-catalyzed intermolecular hydroaminations of challenging 1,4-disubstituted acyclic dienes. Several aryl/alkyl-disubstituted dienes and a sterically differentiated alkyl/alkyl-disubstituted diene undergo coupling with a variety of secondary aliphatic amines, indoline, and primary anilines to generate allylic amines with myriad α-alkyl groups in up to 78% yield, >98:2 rr, and 98.5:1.5 er. A number of experiments, including deuterium labeling and transamination studies, shed light on mechanistic details of the reaction, such as the reversibility of individual steps of the proposed catalytic cycle and of the reaction as a whole.
- Park, Sangjune,Malcolmson, Steven J.
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- A new route to cyclopentenones via ruthenium-catalyzed carbonylative cyclization of allylic carbonates with alkenes
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(equation presented) [RuCl2(CO)3]2/Et3N and (η3-C3H5)RuBr(CO)3/Et 3N are highly effective catalyst systems for carbonylative cyclization of allylic carbonates with alkenes to give the corresponding cyclopentenones in high yields. For example, treatment of allyl methyl carbonate (1a) with 2-norbornene (2a) in the presence of a catalytic amount of [RuCl2(CO)3]2 (2.5 mol %) and Et3N (10 mol %) at 120 °C for 5 h under 3 atm of carbon monoxide gave the corresponding cyclopentenone, exo-4-methyltricyclo[5.2.1.02,6]dec.4.en-3-one (3a), in 80% yield with high stereoselectivity (exo 100%).
- Morisaki, Yasuhiro,Kondo, Teruyuki,Mitsudo, Take-Aki
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- Investigation of bicyclic thioketones as triggers for liquid crystal optical switches
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The axially chiral bicyclic thioketones 11 and 15 were prepared and investigated for suitability as chiroptical triggers in a liquid crystal optical switch. Irradiation of partially resolved 15 with unpolarized light leads to its conversion to the racemic form (photoracemization). However, irradiation of racemic thioketones 11 and 15 with circularly polarized light does not lead to detectable photoresolution. The lack of photoresolution was traced to inefficiency in intramolecular, throughbond triplet energy transfer. These thioketones are not suitable for use as phototriggers.
- Bradford, Rochelle Fisher,Schuster, Gary B.
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- Palladium-catalyzed coupling reactions of functionalized styryl bromides with 1-propenyltributyltin
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The palladium-catalyzed coupling reaction of 1-propenyltributyltin with functionalized styryl bromides is described. 1,3-Dienes are obtained in low to moderate yields except with β,β-dibromostyrene.The latter undergoes a novel organotin-promoted dehydrobromination-coupling sequence to give a 1,3-enyne as final product.Key words: Tin; Palladium; Styryl bromide; Coupling reaction; Bromides; Catalysis
- Zapata, Antonio J.,Ruiz, Jacqueline
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- Synthesis of renewable alkylated naphthalenes with benzaldehyde and angelica lactone
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Herein, we report a new route for the synthesis of renewable alkylated naphthalenes (ANs) with benzaldehyde and angelica lactone, two platform compounds that can be derived from lignocellulose.
- Cong, Yu,Li, Guangyi,Li, Ning,Wang, Aiqin,Wang, Ran,Wang, Xiaodong,Xu, Jilei,Zhang, Tao
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supporting information
p. 5474 - 5480
(2021/08/16)
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- Ni-Catalyzed Regioselective Hydroarylation of 1-Aryl-1,3-Butadienes with Aryl Halides
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An efficient nickel-catalyzed regioselective hydroarylation of 1,3-dienes with aryl halides and a silane has been developed, affording a range of allylic arenes in good to excellent yields under mild conditions. This method exhibits broad substrate scope,
- Wang, Chengdong,Guo, Yingjie,Wang, Xiaoming,Wang, Zheng,Ding, Kuiling
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supporting information
p. 15903 - 15907
(2021/10/07)
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- Iron-Catalyzed Tunable and Site-Selective Olefin Transposition
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The catalytic isomerization of C-C double bonds is an indispensable chemical transformation used to deliver higher-value analogues and has important utility in the chemical industry. Notwithstanding the advances reported in this field, there is compelling demand for a general catalytic solution that enables precise control of the C═C bond migration position, in both cyclic and acyclic systems, to furnish disubstituted and trisubstituted alkenes. Here, we show that catalytic amounts of an appropriate earth-abundant iron-based complex, a base and a boryl compound, promote efficient and controllable alkene transposition. Mechanistic investigations reveal that these processes likely involve in situ formation of an iron-hydride species which promotes olefin isomerization through sequential olefin insertion/β-hydride elimination. Through this strategy, regiodivergent access to different products from one substrate can be facilitated, isomeric olefin mixtures commonly found in petroleum-derived feedstock can be transformed to a single alkene product, and unsaturated moieties embedded within linear and heterocyclic biologically active entities can be obtained.
- Yu, Xiaolong,Zhao, Haonan,Li, Ping,Koh, Ming Joo
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supporting information
p. 18223 - 18230
(2020/12/04)
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- Mild Isomerization of Conjugated Dienes Using Co-Mediated Hydrogen Atom Transfer
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A mild and high yielding rearrangement of 1,3-disubstituted-1,3-dienes to 1,1,4-trisubstituted-1,3-dienes using a cobaloxime catalyst and a silane cocatalyst is reported. Chiral centers near the conjugated diene were not racemized. Deuterium labeling studies are consistent with a hydrogen atom transfer mechanism, and radical intermediates were found to be accessible due to the observed ring opening of a cyclopropane ring.
- Delgado, Kyle R.,Youmans, Dustin D.,Diver, Steven T.
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supporting information
p. 750 - 754
(2020/01/31)
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- Palladium-Catalyzed Regio- A nd Enantioselective Hydrosulfonylation of 1,3-Dienes with Sulfinic Acids: Scope, Mechanism, and Origin of Selectivity
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Chiral sulfones are important structural motifs in organic synthesis because of their widespread use in pharmaceutical chemistry. In particular, chiral allylic sulfones have drawn particular interest because of their synthetic utility. However, enantioselective synthesis of 1,3-disubstituted unsymmetrical chiral allylic sulfones remains a challenge. In this article, we report a protocol for (R)-DTBM-Segphos/Pd-catalyzed regio- A nd enantioselective hydrosulfonylation of 1,3-dienes with sulfinic acids, which provides atom- A nd step-economical access to 1,3-disubstituted chiral allylic sulfones. The reaction occurs under mild conditions and has a broad substrate scope. Combined experimental and computational studies suggest that the reaction is initiated by a ligand-to-ligand hydrogen transfer followed by a C-S bond reductive elimination via a six-membered transition state. Steric repulsion between the olefinic C-H of the substrate and the tert-butyl group of (R)-DTBM-Segphos was found to be a key factor in the enantiocontrol.
- Dong, Dongfang,Zhang, Qinglong,Zi, Weiwei
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supporting information
p. 15860 - 15869
(2020/10/18)
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- Migratory Hydrogenation of Terminal Alkynes by Base/Cobalt Relay Catalysis
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Migratory functionalization of alkenes has emerged as a powerful strategy to achieve functionalization at a distal position to the original reactive site on a hydrocarbon chain. However, an analogous protocol for alkyne substrates is yet to be developed. Herein, a base and cobalt relay catalytic process for the selective synthesis of (Z)-2-alkenes and conjugated E alkenes by migratory hydrogenation of terminal alkynes is disclosed. Mechanistic studies support a relay catalytic process involving a sequential base-catalyzed isomerization of terminal alkynes and cobalt-catalyzed hydrogenation of either 2-alkynes or conjugated diene intermediates. Notably, this practical non-noble metal catalytic system enables efficient control of the chemo-, regio-, and stereoselectivity of this transformation.
- Liu, Bingxue,Liu, Qiang,Liu, Xufang
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supporting information
p. 6750 - 6755
(2020/03/13)
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- Transition-Metal-Free Allylic Borylation of 1,3-Dienes
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This work explains the reactivity of diboron reagents with 1,3-dienes in a transition-metal-free context. The sole addition of Na2CO3 (30 mol %) to bis(pinacolato)diboron in MeOH allows the 1,4-hydroboration of cyclic and noncyclic 1,3-dienes. The electronic influence on the substrate guarantees the conjugated 1,4-hydroboration versus 1,2-diboration. DFT calculations show that the distribution of charge in the allylic anion intermediate governs the selectivity toward 1,4-hydroboration, while the favored trans configuration in diene reagents determines the preference for the E allyl boronate products.
- Maza, Ricardo J.,Davenport, Elliot,Miralles, Núria,Carbó, Jorge J.,Fernández, Elena
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supporting information
p. 2251 - 2255
(2019/04/10)
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- Transition-metal-free synthesis of vicinal triborated compounds and selective functionalisation of the internal C-B bond
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1,2,3-Triborated compounds can be prepared by simple nucleophilic borylation of 1,3-dienes, without the assistance of metal catalysts. Selective functionalisation of the internal C-B bond of the 1,2,3-triborated compounds, through cross-coupling with aryl
- Davenport, Elliot,Fernandez, Elena
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supporting information
p. 10104 - 10107
(2018/09/18)
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- Ligand-Free Iron-Catalyzed Carbon(sp2)-Carbon(sp2) Cross-Coupling of Alkenyllithium with Vinyl Halides
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An efficient ligand-free iron-catalyzed cross-coupling reaction involving alkenyllithium and vinyl iodides was developed to form diene species in moderate to good yields. This new iron-catalyzed cross-coupling reaction provides a mild, inexpensive, and environmentally friendly avenue toward synthesis of diversified diene derivatives.
- Liu, Qiang,Wang, Zhi-Yong,Peng, Xiao-Shui,Wong, Henry N. C.
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supporting information
p. 6325 - 6333
(2018/06/01)
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- Flow Dehydration and Hydrogenation of Allylic Alcohols: Application to the Waste-Free Synthesis of Pristane
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Hydroxy-substituted sulfonic acid functionalized silica (HO-SAS) in combination with THF containing a small amount of water as a solvent proved to be a reliable system for the dehydration of allylic alcohols. This process generally caused dehydration within 1 min through a column reactor charged with HO-SAS. The flow dehydration was sequenced by flow hydrogenation, which resulted in the synthesis of pristane. A scalable flow synthesis of pristane was successfully performed and afforded 10 g of pristane after an operation of 2 h. We also performed dehydration and hydrogenation by using a mixed column of HO-SAS and 10 % Pd/C.
- Furuta, Akihiro,Hirobe, Yuki,Fukuyama, Takahide,Ryu, Ilhyong,Manabe, Yoshiyuki,Fukase, Koichi
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supporting information
p. 1365 - 1368
(2017/03/23)
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- Chiral Pincer Carbodicarbene Ligands for Enantioselective Rhodium-Catalyzed Hydroarylation of Terminal and Internal 1,3-Dienes with Indoles
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Catalytic enantioselective addition of N-heteroarenes to terminal and internal 1,3-dienes is reported. Reactions are promoted by 5 mol % of Rh catalyst supported by a new chiral pincer carbodicarbene ligand that delivers allylic substituted arenes in up to 95% yield and up to 98:2 er. Mechanistic and X-ray evidence is presented that supports that the reaction proceeds via a Rh(III)-η3-allyl.
- Marcum, Justin S.,Roberts, Courtney C.,Manan, Rajith S.,Cervarich, Tia N.,Meek, Simon J.
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supporting information
p. 15580 - 15583
(2017/11/14)
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- Direct catalytic cross-coupling of alkenyllithium compounds
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A catalytic method for the direct cross-coupling of alkenyllithium reagents with aryl and alkenyl halides is described. The use of a catalyst comprising Pd2(dba)3/XPhos allows for the stereoselective preparation of a wide variety of substituted alkenes in high yields under mild conditions. In addition (1-ethoxyvinyl)lithium can be efficiently converted into substituted vinyl ethers which, after hydrolysis, give readily access to the corresponding methyl ketones in a one pot procedure.
- Hornillos, Valentn,Giannerini, Massimo,Vila, Carlos,Faans-Mastral, Martn,Feringa, Ben L.
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p. 1394 - 1398
(2015/02/19)
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- Catalytic stereospecific allyl-allyl cross-coupling of internal allyl electrophiles with allylB(pin)
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Application of internal electrophiles in catalytic stereospecific allyl-allyl cross-coupling enable the rapid construction of multisubstituted 1,5-dienes, including those with all carbon quaternary centers. Compounds with minimal steric differentiation ca
- Le, Hai,Batten, Amanda,Morken, James P.
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p. 2096 - 2099
(2014/05/06)
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- An approach to the regioselective diamination of conjugated di- and trienes
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It's do or diaminate: The selective diamination of 1,3-butadienes in the presence of hypervalent iodine reagents has been developed. This oxidation process proceeds with complete selectivity in favor of diamination. Depending on the substrate, it proceeds either with 1,2- or 1,4-regioselectivity (see scheme). Copyright
- Lishchynskyi, Anton,Muniz, Kilian
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supporting information; experimental part
p. 2212 - 2216
(2012/03/27)
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- Palladium-catalyzed allylic fluorination of cinnamyl phosphorothioate esters
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A highly regioselective, Pd-catalyzed allylic fluorination of phosphorothioate esters is reported. This chemistry addresses several limitations of previously reported methods in which elimination and lack of reactivity were problematic. Preliminary mechanistic investigations reveal that these reactions are stereospecific and provide fluorinated products with net retention of stereochemical configuration. In analogy to other Pd-catalyzed allylic substitution reactions, this process likely proceeds through a palladium π-allyl intermediate.
- Lauer, Andrew M.,Wu, Jimmy
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supporting information
p. 5138 - 5141,4
(2012/12/12)
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- Palladium-catalyzed allylic fluorination of cinnamyl phosphorothioate esters
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A highly regioselective, Pd-catalyzed allylic fluorination of phosphorothioate esters is reported. This chemistry addresses several limitations of previously reported methods in which elimination and lack of reactivity were problematic. Preliminary mechanistic investigations reveal that these reactions are stereospecific and provide fluorinated products with net retention of stereochemical configuration. In analogy to other Pd-catalyzed allylic substitution reactions, this process likely proceeds through a palladium π-allyl intermediate.
- Lauer, Andrew M.,Wu, Jimmy
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supporting information
p. 5138 - 5141
(2013/01/15)
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- Nickel-catalyzed allylic substitution of simple alkenes
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This report describes a nickel-catalyzed allylic substitution process of simple alkenes whereby an important structural motif, a 1,4-diene, was prepared. The key to success is the use of an appropriate nickel-phosphine complex and a stoichiometric amount of silyl triflate. Reactions of 1-alkyl-substituted alkenes consistently provided 1,1-disubstituted alkenes with high selectivity. Insight into the reaction mechanism as well as miscellaneous application of the developed catalytic process is also documented.
- Matsubara, Ryosuke,Jamison, Timothy F.
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p. 1860 - 1875
(2012/02/02)
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- An efficient, overall [4+1] cycloadditon of 1,3-dienes and nitrene precursors
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Intermolecular cycloadditions of conjugated dienes and nitrene precursors usually produce aziridines. A generally useful method was lacking to directly provide the [4+1] cycloadducts, 3-pyrrolines. We have realized this transformation by using an uniquely active catalyst, copper(II) 1,1,1,5,5,5-hexafluoroacetylacetonate ([Cu(hfacac)2]). The method is applicable to a wide array of dienes with good yields. When 1,4-disubsituted dienes are used as substrates, good-to-excellent cis or trans selectivity can be obtained. Interestingly, the cis or trans preference depends on the nature of the substituents, rather than diene geometry. Mechanistic studies reveal that the [4+1] cycloaddition proceeds through diene aziridination and subsequent ring expansion. Among common copper catalysts, only [Cu(hfacac)2] can efficiently catalyze both steps, which explains the unique efficiency of the catalyst.
- Wu, Qiong,Hu, Jian,Ren, Xinfeng,Zhou, Jianrong
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p. 11553 - 11558
(2011/11/29)
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- Synthesis of 1,4-diarylbuta-1,3-dienes through palladium-catalyzed decarboxylative coupling of unsaturated carboxylic acids
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It has been found that readily available hydroxylated cinnamic acids such as ferulic acid undergo palladium-catalyzed decarboxylative coupling with aryl iodides and internal alkynes in a 1:1:1 manner to produce 1,4-diarylbuta-1,3- dienes. The butadiene synthesis has also been achieved through the coupling of aryl halides with dienoic acids. Some of the products exhibit solid-state fluorescence.
- Yamashita, Mana,Hirano, Koji,Satoh, Tetsuya,Miura, Masahiro
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experimental part
p. 631 - 636
(2011/04/26)
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- Regioselective rhodium-catalyzed hydroformylation of 1,3-dienes to highly enantioenriched β,γ-unsaturated aldehyes with diazaphospholane ligands
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Regioselective and enantioselective rhodium-catalyzed hydroformylation of 1,3-dienes with chiral bisdiazaphospholane ligands yields β,γ- unsaturated aldehydes that retain a C=C functionality for further conversion. The reaction conditions are mild, featuring low catalyst loadings (0.5 mol %), pressures readily obtained in glass bottles, and convenient reaction times (1.5-12 h). Optimized reaction conditions produce high enantioselectivity (>90% ee), regioselectivity (88-99%), and conversion to β,γ- unsaturated aldehydes (99%) for ten 1,3-dienes encompassing a variety of substitution patterns.
- Watkins, Avery L.,Landis, Clark R.
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p. 164 - 167
(2011/04/12)
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- Tunable stereoselective alkene synthesis by treatment of activated imines with nonstabilized phosphonium ylides
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A broad range of readily accessible N-sulfonyl imines undergo olefination reaction with nonstabilized phosphonium ylides under mild conditions to afford an array of both Z- and E-isomers of 1,2-disubstituted alkenes, allylic alcohols, and allylic amines in good yields and with greater than 991 stereoselectivity.
- Dong, De-Jun,Li, Yuan,Wang, Jie-Qi,Tian, Shi-Kai
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supporting information; experimental part
p. 2158 - 2160
(2011/03/20)
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- Palladium-catalyzed hydroarylation of 1,3-dienes with boronic esters via reductive formation of π-Allyl palladium intermediates under oxidative conditions
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A palladium-catalyzed reductive cross-coupling of 1,3-dienes with boronic esters in which a π-allyl Pd species is generated directly from a 1,3-diene via a Pd-catalyzed aerobic alcohol oxidation is reported. Both the scope of the process and the origin of a highly selective 1,2-addition are discussed.
- Liao, Longyan,Sigman, Matthew S.
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supporting information; experimental part
p. 10209 - 10211
(2010/09/05)
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- Nickel-catalyzed allylic substitution of simple alkenes
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Nickel-catalyzed intermolecular allylic substitution of simple alkenes (ethylene and alpha olefins) is described. This method is the first catalytic intermolecular process for direct allylation of nonconjugated, nonstrained simple alkenes. Catalyst loadings as low as 2.5 mol % Ni afford the desired product in high yield in both gram-scale and smaller scale coupling reactions.
- Matsubara, Ryosuke,Jamison, Timothy F.
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supporting information; experimental part
p. 6880 - 6881
(2010/07/05)
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- Palladium-catalyzed elimination reaction of acyclic (E)-allylic acetates: The stereochemistry elucidated by syn-effect
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The stereochemistry of the elimination reaction of acyclic (E)-allylic acetates into the corresponding 1,3-dienes catalyzed by palladium in the presence of a base was investigated. The Z/E ratios of the resulting 1,3-dienes varied with the δ-substituents of the starting allylic acetates. This phenomenon was discussed based on the concept of a syn-effect, which is most primarily rationalized by a σ → π* interaction. Copyright
- Takenaka, Hiroyuki,Ukaji, Yutaka,Inomata, Katsuhiko
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p. 256 - 257
(2007/10/03)
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- New mechanistic aspects on the catalytic transformation of vinylthiiranes to mono and disubstituted 3,6-dihydro-1,2-dithiins by tungsten pentacarbonyl monoacetonitrile
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Various alkyl and aryl mono- and disubstituted 3,6-dihydro-1,2-dithiins have been synthesised from their corresponding vinylthiiranes exploiting Adams' tungsten pentacarbonyl monoacetonitrile catalytic transformation. New conclusions pertaining to the rate determining step, the sensitivity of the process to precursor sterics and electronics, and the nature of various reaction intermediates are highlighted.
- Lupton, David W,Taylor, Dennis K
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p. 4517 - 4527
(2007/10/03)
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- Stereochemistry of Carbenic 1,2-Vinyl Shifts
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Various 1-phenylbut-3-enylidenes, (Ph)CCR2CH=CHR', were generated thermally and photolytically from tosylhydrazone (diazo) precursors. 1,2-Vinyl shifts, leading to 1,3-dienes, R′CH=CHC(Ph)=CR2, were found to predominate over γ-C-H insertion (R = Me) and to compete with 1,2-H shifts (R = H). Intramolecular addition to the double bond was detected in the case of R = R′ = Me. The resulting bicyclobutane is thermally stable and does not mediate the vinyl shift. Stereospecific migration of 1-propenyl groups (R′ = Me), with retention of configuration, was observed on thermolysis and direct photolysis of appropriate substrates. These data exclude the intervention of a triplet diradical and point to vinyl migration in the singlet manifold. Benzophenone-sensitized generation of the carbenes led to partial stereomutation but did not provide conclusive evidence for a triplet rearrangement (isomerization of the diene products could not be avoided under these conditions).
- Kirmse, Wolfgang,Kopannia, Siegfried
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p. 1178 - 1184
(2007/10/03)
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- Forbidden reactions, II. - The disrotatory cyclobutene ringopening
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The energy profiles for the con- and disrotatory opening of benzocyclobutene, methylenecyclobutene, and cyclobutene derivatives were established by NO and oxygen trapping. The enthalpy for the transition states for the "forbidden" reactions proofed to be identical with the heat of formation of the orthogonal diradicals derived by geometrical isomerization of the dienes formed in these reactions. These diradicals describe very well the activation barriers observed for the disrotatory opening of bicyclic cyclobutenes ([3.2.0] and [2.2.0] systems), but not for bicyclo[2.1.0]pent-2-ene, indicating here a truly forbidden reaction. VCH Verlagsgesellschaft mbH, 1996.
- Roth, Wolfgang R.,Rekowski, Volker,Boerner, Sabine,Quast, Michael
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p. 409 - 430
(2007/10/03)
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- KINETICS OF THE PTC-WITTIG REACTIONS OF 2-BUTENYLMETHYLDIPHENYLPHOSPHONIUM YLIDS
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The kinetics and linear free energy relationship of PTC-Wittig reaction between substituted aromatic aldehydes and title compound are discussed.
- Huang, Wenfang,Ding, Mingwu,Xiao, Wenjing,Wu, Tianjie
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- REDUCTION OF ALLYLIC ACETATES BY USING A NOVEL Pd(O)-SmI2 SYSTEM
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Allylic acetates were reduced to alkenes in high yields with SmI2 and 2-propanol in the presence of a catalytic amount of palladium(O) complex.
- Tabuchi, Takanori,Inanaga, Junji,Yamaguchi, Masaru
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p. 601 - 602
(2007/10/02)
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- An E-Selective 1,3-Diene Synthesis from Moderated Ylides and Aldehydes
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The synthesis of E-1,3-dienes by the Wittig reaction of aldehydes and ylides is described.
- Vedejs, E.,Fang, Huang Wen
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p. 210 - 212
(2007/10/02)
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- Palladium-Catalyzed Syntheses of Aryl Polyenes
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The palladium-catalyzed arylation reaction has been employed to prepare a variety of mono- and diaryl 1,3-dienes and 1,3,5-trienes.The yields were good when electron withdrawing substituents were present in the aryl groups but only poor to fair when electron-donating groups were involved.Monoaryl dienes and trienes reacted well with all types of aryl halides to give mixed diaryl derivatives. 2-Bromostyrene reacts with phenylhexatriene to form 1,8-diphenyloctatetraene and with hexatriene to form 1,10-diphenyldecapentaene, but both only in about 15percent yield.
- Mitsudo, Taki-aki,Fischetti, William,Heck, Richard F.
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p. 1640 - 1646
(2007/10/02)
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- COMPLEXES OF TRANSITION METALS IN THE CHEMISTRY OF CONJUGATED SYSTEMS. III. REACTION OF DIENE HYDROCARBONS WITH ORGANOMAGNESIUM COMPOUNDS IN THE PRESENCE OF SALTS AND COMPLEXES OF TRANSITION METALS
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The effect of the structure of the reagents and the nature of the catalyst on the direction and selectivity in the reaction of 1,3-dienes and their derivatives with aromatic Grignard reagents was investigated.It was shown that in the presence of salts and complexes of iron(III) 1,3-alkadienes R1CH=C(R2)C(R3)=CH2 react with arylmagnesium halides to form trans-(E)-1-aryl-1,3-alkadienes, whereas the sterically hindered (R2, R3=CH3) cyclic 1,3-alkadienes and also 1,2-alkadienes give mainly adducts (1:1).Catalysis by the phosphine complexes of nickel(II) leads to the formation of telomeric (2:1) (E)-1-aryl-2,7- and (E,E)-1-aryl-2,6-alkadienes.The results demonstrate the determining role of the stereochemical conditions for the coordination of the diene in the course of the reaction and also the significant contribution from the processes of one-electron reduction of the catalyst.
- Zubritskii, L. M.,Romashchenkova, N. D.,Petrov, A. A.
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p. 2157 - 2167
(2007/10/02)
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- Anwendungen der Phasentransfer-Katalyse 17. Wittig-Reaktionen in verschiedenen Zweiphasen-Systemen
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EINE vergleichende Untersuchung von Wittig-Reaktionen unter Phasentransfer-Katalyse (PTC) bei verschiedenen Bedingungen wurde durchgefuehrt.Es erwies sich als unnoetig, ausser den Phosphoniumsalzen einen PTC-Katalysator zu verwenden.Mechanistische Konsequenzen dieses Befundes werden diskutiert.Als ein besonders geeignetes Basensystem stellte sich Kalium-tert-butoxid in Benzol heraus.Erstmals gelang die Umzetzung von Ketonen und aliphatischen Aldehyden.Einige sehr hohe Literaturausbeuten von PTC-Wittig-Reaktionen konnten unter praeparativen Bedingungen nicht reproduziert werden.
- Dehmlow, Eckehard V.,Barahona-Naranjo, Simon
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p. 1748 - 1762
(2007/10/02)
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- DIMETHYL SULFOXIDE-CATALYTIC MOLYBDENUM PEROXIDE: A NEW SYSTEM FOR THE FACILE OXIDATION OF ALCOHOLS
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In the dimethyl sulfoxide (DMSO)-metal oxide oxidation of alcohol to carbonyl compound, molybdenum oxides were the only useful catalytic reagents, and various alcohols were oxidized to the corresponding carbonyl compounds in high yields.
- Masuyama, Yoshiro,Tsuhako, Akira,Kurusu, Yasuhiko
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p. 3973 - 3976
(2007/10/02)
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- Anwendungen der Phasentransfer-Katalyse 18. Horner-Emmons Reaktionen
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Optimale Bedingungen fuer die Darstellung von Olefinen aus den relativ wenig aktivierten Benzyl-, Cinnamyl- und Crotonylphosphonestern wurden aufgesucht.Als Carbonylkomponenten koennen aromatische Aldehyde und (mit verminderten Ausbeuten) auch aliphatische Aldehyde und Ketone eingesetzt werden.Die beste Basen-Loesungsmittel-Katalysator-Kombination ist Benzol/gepulvertes KOH/18-Krone-6.Im Gegensatz zur phasentransfer-Katalytischen Wittig-Reaktion wird die Ausbeute bei der Horner-Reaktion durch die Gegenwart des Kronenethers verbessert.Mechanistische Schlussfolgerungen aus diesem Befund werden diskutiert.
- Dehmlow, Eckehard V.,Barahona-Naranjo, Simon
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p. 1763 - 1771
(2007/10/02)
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- Additions of Carboxylic Acid Dianions to α,β-Unsaturated Carbonyl Compounds - Control of the 1,2-/1,4-Regioselectivity by Steric Substituent Effects
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Dilithium carboxylic acid dianions 1 attack α,β-unsaturated aldehydes (2) 1,2-regiospecifically with formation of the unsaturated β-hydroxy carboxylic acids 3/4.Additionally, the addition of the phenylacetate dianion 1a can be conducted to the threo-isomer with high selectivity by reversible reaction. - α,β-Enones (8) add 1 irreversibly in 1,2- and 1,4-position.Depending on the substitution pattern, the whole range from pure 1,2- to pure 1,4-adduct is covered.The influence of the 1-counterion M and of the solvent is significant; the 1,4-portion increases with the complexing effect of M and with the Lewis-basicity of the solvent.
- Mulzer, Johann,Bruentrup, Gisela,Hartz, Georg,Kuehl, Uwe,Blaschek, Ursula,Boehrer, Gerald
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p. 3701 - 3724
(2007/10/02)
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