- Catalytic studies of cyclometalated gold(III) complexes and their related UiO-67 MOF
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Cyclometalated gold(III) complexes Au(L)(OAcF)2 (L = phenylpyridine dicarboxylic diester (ppyde) or phenylpyridine dicarboxylic acid (ppydc)) have been prepared reacting Au(OAc)3 with corresponding phenyl pyridines (ppyde or ppydc) in trifluoroacetic acid (HOAcF) under microwave heating. Further treatment of Au(L)(OAcF)2 with aqua regia resulted in dichloro complexes Au(L)Cl2. Au-functionalized UiO-67 MOF has been synthesized by exchanging linkers of UiO-67 with Au(ppydc)Cl2, furnishing the MOF with (N^C)-cyclometalated Au(III) centers. The catalytic activities of the molecular cyclometalated complexes and the Au-incorporated MOF were studied in gold-catalyzed propargyl ester cyclopropanations. Almost all complexes and the MOF showed catalytic activity to the cyclopropanation product (up to 97% conversion), with a preference for the trans diastereoisomer (up to 14:86 d.r.). The recyclability of the most active molecular complex has also been investigated.
- ?ien-?degaard, Sigurd,Fiksdahl, Anne,Kaur, Gurpreet,Levchenko, Volodymyr A.,Siah, Huey-San Melanie,Tilset, Mats
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- Trialkylborane-Mediated Multicomponent Reaction for the Diastereoselective Synthesis of Anti-δ,δ-Disubstituted Homoallylic Alcohols
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The trialkylborane/O2-mediated reaction of propargyl acetates having a tributylstannyl group at an alkyne terminus with aldehydes in a THF-H2O solvent system gave anti-δ,δ-disubstituted homoallylic alcohols with good to high diastereoselectivity. Intriguingly, two alkyl groups derived from trialkylborane were embedded into the reaction product. The trialkylborane plays a key role not only as a radical initiator but also as a source of alkyl radicals.
- Horino, Yoshikazu,Murakami, Miki,Aimono, Ataru,Lee, Jun Hee,Abe, Hitoshi
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supporting information
p. 476 - 480
(2019/01/14)
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- Neighboring Carbonyl Group Assisted Oxyacetoxylation of Propargylic Carboxylates with Retention of Chirality under Metal Free Condition
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A metal-free oxyacetoxylation method of primary, secondary and tertiary propargylic carboxylates with retention of chirality was presented. The reaction proceeds through the intramolecular nucleophilic attack of the neighboring carbonyl group on an alkynyliodonium intermediate. The process is general with broad substrate scope and is amenable for application to a variety of propargyl carboxylates including those obtained from natural products. Insight into the mechanistic pathway by isotopic labelling (using H2O18 and D2O) and controlled experiments confirmed. (Figure presented.).
- Pradhan, Tapas R.,Mohapatra, Debendra K.
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supporting information
p. 3605 - 3611
(2019/07/04)
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- Trialkylborane-Mediated Propargylation of Aldehydes Using γ-Stannylated Propargyl Acetates
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A transition-metal-free three-component process that combines aldehydes, 3-(tributylstannyl)propargyl acetates formed in situ from readily available propargyl acetates, and trialkylboranes provides access to a range of 1,2,4-trisubstituted homopropargylic alcohols. The addition of diisopropylamine plays a crucial role in the selective formation of homopropargylic alcohols. Importantly, this methodology can be extended to a single-flask reaction sequence starting from propargyl acetates.
- Horino, Yoshikazu,Murakami, Miki,Ishibashi, Mayo,Lee, Jun Hee,Watanabe, Airi,Matsumoto, Rio,Abe, Hitoshi
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supporting information
p. 9564 - 9568
(2019/12/24)
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- Palladium- and Rhodium-Catalyzed Dynamic Kinetic Resolution of Racemic Internal Allenes Towards Chiral Pyrazoles
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A complementing Pd- and Rh-catalyzed dynamic kinetic resolution (DKR) of racemic allenes leading to N-allylated pyrazoles is described. Such compounds are of enormous interest in medicinal chemistry as certified drugs and potential drug candidates. The new methods feature high chemo-, regio- and enantioselectivities aside from displaying a broad substrate scope and functional group compatibility. A mechanistic rational accounting for allene racemization and trans-alkene selectivity is discussed.
- Hilpert, Lukas J.,Sieger, Simon V.,Haydl, Alexander M.,Breit, Bernhard
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supporting information
p. 3378 - 3381
(2019/02/06)
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- Cu-Pybox catalyzed synthesis of 2,3-disubstituted imidazo[1,2-a]pyridines from 2-aminopyridines and propargyl alcohol derivatives
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A highly efficient cascade sequence for syntheses of 2,3-disubstituted imidazo[1,2-a]pyridines with exclusive regioselectivity in moderate to excellent yields has been developed. This cascade was initiated through propargylation of 2-aminopyridines at pyridine-nitrogen with propargyl alcohol derivatives using Cu(II)-Pybox as catalyst and followed by an intramolecular cyclization and isomerization. Besides 2-aminopyridine, less reactive 2-aminopyrimidine, 2-aminopyrazine and 3-aminopyridazine were also suitable in this cascade.
- Cheng, Cang,Ge, Luo,Lu, Xuehe,Huang, Jianping,Huang, Haocheng,Chen, Jie,Cao, Weiguo,Wu, Xiaoyu
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p. 6866 - 6874
(2016/10/04)
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- Diastereo- and enantioselective propargylation of benzofuranones catalyzed by pybox-copper complex
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Diastereo- and enantioselective preparation of 2,2-disubstituted benzofuran-3(2H)-one has been realized by a pybox-copper catalyzed reaction between 2-substituted benzofuran-3(2H)-one and propargyl acetate. The utility of this method was demonstrated by further transformation of the terminal alkyne into a methyl ketone without loss of enantiomeric purity.
- Zhao, Long,Huang, Guanxin,Guo, Beibei,Xu, Lijun,Chen, Jie,Cao, Weiguo,Zhao, Gang,Wu, Xiaoyu
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supporting information
p. 5584 - 5587
(2015/02/19)
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- Stereocontrol in palladium-catalyzed propargylic substitutions: Kinetic resolution to give enantioenriched 1,5-enynes and propargyl acetates
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Kinetic resolution during the catalytic allyl-propargyl cross-coupling with chiral starting materials can be accomplished with a chiral palladium catalyst. These reactions offer ready access to enantiomerically enriched enyne products from simple, readily
- Ardolino, Michael J.,Eno, Meredith S.,Morken, James P.
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supporting information
p. 3413 - 3419
(2013/12/04)
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- Construction of 1,5-enynes by stereospecific Pd-catalyzed allyl-propargyl cross-couplings
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The palladium-catalyzed cross-coupling of chiral propargyl acetates and allyl boronates delivers chiral 1,5-enynes with excellent levels of chirality transfer and can be applied across a broad range of substrates.
- Ardolino, Michael J.,Morken, James P.
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supporting information; experimental part
p. 8770 - 8773
(2012/07/02)
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- Enantioselective copper-catalysed propargylic substitution: Synthetic scope study and application in formal total syntheses of (+)-anisomycin and (-)-cytoxazone
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A copper catalyst with a chiral pyridine-2,6-bisoxazoline (pybox) ligand was used to convert a variety of propargylic esters with different side chains (R=Ar, Bn, alkyl) into their amine counterparts in very high yields and with good enantioselectivities (up to 90% enantiomeric excess (ee)). Different amine nucleophiles were applied in the reactions and the highest enantioselectivities were obtained for aniline and its analogues. Interestingly, some carbon nucleophiles could also be used and with indoles excellent ee values were obtained (up to 98% ee). The versatility of the propargylic amines obtained was demonstrated by their further elaboration to formal total syntheses of the antibiotic (+)-anisomycin and the cytokine modulator (-)-cytoxazone. Copyright
- Detz, Remko J.,Abiri, Zohar,Le Griel, Remi,Hiemstra, Henk,Van Maarseveen, Jan H.
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supporting information; experimental part
p. 5921 - 5930
(2011/06/26)
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- Asymmetrie copper-catalyzed propargylic substitution reaction of propargylic acetates with enamines
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Enamines served as carbon-nucleophiles for the first time In the Cu-catalyzed asymmetric propargylic substitution reaction of propargylic acetates, providing corresponding chiral β-ethynyl-substituted ketones In high yields and In good to high enantioselectivity.
- Fang, Ping,Hou, Xue-Long
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supporting information; experimental part
p. 4612 - 4615
(2009/12/09)
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- Enantioselective copper-catalyzed propargylic amination
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(Chemical Equation Presented) A proper copper catalyst with a chiral pyridine-2,6-bisoxazoline (pybox) ligand was used to convert a variety of propargylic acetates with aromatic side chains (R = Ar) into their amine counterparts in high yield and with good selectivity (up to 88% ee). The resulting chiral propargylic amines can be elaborated further into P,N ligands (see scheme; DIPEA = diisopropylethylamine).
- Detz, Remko J.,Delville, Marielle M. E.,Hiemstra, Henk,Van Maarseveen, Jan H.
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p. 3777 - 3780
(2008/12/23)
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- [(NHC)AuI]-catalyzed formation of conjugated enones and enals: An experimental and computational study
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The [(NHC)AuI]-catalyzed (NHC = N-heterocyclic carbene) formation of α,β-unsaturated carbonyl compounds (enones and enals) from propargylic acetates is described. The reactions occur at 60°C in 8 h in the presence of an equimolar mixture of [(NHC)AuCl] and AgSbF6 and produce conjugated enones and enals in high yields. Optimization studies revealed that the reaction is sensitive to the solvent, the NHC, and, to a lesser extent, to the silver salt employed, leading to the use of [(ItBu)AuCl]/ AgSbF6 in THF as an efficient catalytic system. This transformation proved to have a broad scope, enabling the stereoselective formation of (E)-enones and -enals with great structural diversity. The effect of substitution at the propargylic and acetylenic positions has been investigated, as well as the effect of aryl substitution on the formation of cinnamyl ketones. The presence or absence of water in the reaction mixture was found to be crucial. From the same phenylpropargyl acetates, anhydrous conditions led to the formation of indene compounds via a tandem [3,3] sigmatropic rearrangement/intramolecular hydroarylation process, whereas simply adding water to the reaction mixture produced enone derivatives cleanly. Several mechanistic hypotheses, including the hydrolysis of an allenol ester intermediate and SN2′ addition of water, were examined to gain an insight into this transformation. Mechanistic investigations and computational studies support [(NHC)AuOH], produced in situ from [(NHC)AuSbF6] and H 2O, instead of cationic [(NHC)AuSbF6] as the catalytically active species. Based on DFT calculations performed at the B3LYP level of theory, a full catalytic cycle featuring an unprecedented transfer of the OH moiety bound to the gold center to the C≡C bond leading to the formation of a gold-allenolate is proposed.
- Marion, Nicolas,Carlqvist, Peter,Gealageas, Ronan,De Fremont, Pierre,Maseras, Feliu,Nolan, Steven P.
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p. 6437 - 6451
(2008/02/13)
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- Aryl propargylic alcohols of high enantiomeric purity via lipase catalyzed resolutions
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A variety of substituted aryl propargylic alcohols were prepared via lipase catalyzed resolutions, the enantioselective hydrolysis of the corresponding esters being the method of choice.
- Waldinger, Claudia,Schneider, Manfred,Botta, Maurizio,Corelli, Federico,Summa, Vincenzo
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p. 1485 - 1488
(2007/10/03)
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- MEDICINAL PLANTS OF SOUTHERN AFRICA. PART 2. SYNTHESIS OF 1,3-BIS-(4-METHOXYPHENYL)PENTA-1,4-DIENE, A STEREOISOMER OF DIMETHYLHINOKIRESINOL, AND ITS 4-MONOMETHOXY ANALOGUE
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A six-step synthesis of the title compounds (6) and (7) from prop-2-yn-1-ol, and proceeding via 3-(4-methoxyphenyl)prop-1-yne, is described.Detailed 1H n.m.r. spectral analysis (500 MHz) suggests that the synthetic compounds have a 1,2-E stereochemistry in contrast to the Z-configuration present in the naturally occurring hinokiresinol (3).By utilizing a different, and much less efficient route, a small quantity of (Z)-3-(4-methoxyphenyl)-1-phenylpenta-1,4-diene (5) was obtained.
- Ameer, Farouk,Drewes, Siegfried E.,Drewes, Mark W.,Roos, Gregory H. P.,Watson, Martin C.
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p. 1425 - 1430
(2007/10/02)
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