- One-Pot Synthesis of N-H-Free Pyrroles from Aldehydes and Alkynes
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The first base-mediated intermolecular cyclization of arylaldehydes and terminal arylacetylenes for the synthesis of a wide range of pyrroles in a single step has been described. The developed methodology used commercially available starting materials and
- Chen, Lai,Huo, Jing-Qian,Kou, Song,Mao, Jianyou,Si, He-Long,Xu, Xin-Yu,Zhang, Jin-Lin
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Read Online
- Asymmetric addition of terminal acetylenes to aldehydes, catalyzed by Zn(OTf)2-cinchona alkaloid complexes
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Cinchona alkaloids in combination with zinc triflate catalyze the addition of acetylenes to aldehydes at room temperature with ee up to 89% for aliphatic aldehydes. Cinchonidine has proven to be the ligand of choice for the addition reaction whose outcome
- Ekstr?m, Jesper,Zaitsev, Alexey B.,Adolfsson, Hans
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Read Online
- Formation of β-Oxo- N-vinylimidates via Intermolecular Ester Incorporation in Huisgen Cyclization/Carbene Cascade Reactions
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Unusual intermolecular trapping of esters by carbenes generated via a Huisgen cyclization/retroelectrocyclization/dediazotization cascade reaction is presented. β-Oxo-N-vinylimidates could be obtained in one step from propargyl carbonazidates. Mechanistic control experiments suggested reversible dipole formation by ester addition to the carbene, and nitrogen attack to the ester carbonyl was irreversibly followed by stereoselective decarboxylative elimination to give the Z-vinyl imidate. The cross-conjugated enone, imidate, and enamine functional groups in the β-oxo-N-vinylimidates offer novel syntheses of functionalized oxazoles.
- Wang, Qinxuan,May, Jeremy A.
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supporting information
p. 9579 - 9584
(2021/01/09)
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- Regioselective Iron-Catalysed Cross-Coupling Reaction of Aryl Propargylic Bromides and Aryl Grignard Reagents
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An iron-catalysed Kumada-type cross-coupling reaction between aryl substituted propargylic bromides and arylmagnesium reagents has been developed. Propargylic coupling products were the main or only outcome, and propargyl/allene regioselectivity was shown to depend on the electronic nature of the substituents on the triple bond of the substrate and on the arylmagnesium halide. Best selectivities were observed when electron donating substituents were present in either reagent. The process is stereoespecific, occurs with configuration inversion and no carbon-based radicals seem to be involved in the mechanism. (Figure presented.).
- Manjón-Mata, Inés,Quirós, M. Teresa,Bu?uel, Elena,Cárdenas, Diego J.
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supporting information
p. 146 - 151
(2019/12/11)
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- Alkylation of Terminal Alkynes under Zinc Lewis Acid Catalysis and Its Mechanistic Studies
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With a zinc Lewis acid catalyst and proton sponge in toluene, terminal alkynes were found to undergo the alkylation by alkyl triflates to provide unsymmetrical internal alkynes. This is the first example that a simple alkyl chain other than benzylic and norbornyl units can be introduced onto the alkynyl carbon atom under Lewis acid catalysis. Mechanistic studies revealed that the activation of the alkyne by the zinc Lewis acid and proton sponge is the trigger of the reaction to give a monoalkynylzinc species, which successively reacts with the alkyl triflate to afford the internal alkyne. A radical pathway is unlikely in this system. (Figure presented.).
- Osano, Mana,Kida, Takeru,Yonekura, Kyohei,Tsuchimoto, Teruhisa
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supporting information
p. 2825 - 2831
(2019/04/13)
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- Transition-metal-free C-C σ-bond activation of α-aryl ketones and subsequent Zn-catalyzed intramolecular cyclization: synthesis of tetrasubstituted furans
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A highly atom-economical protocol for the synthesis of tetrasubstituted furans has been developed. This process is realized through the tandem reactions of Cs2CO3 promoted C-C σ-bond activation of α-aryl ketones followed by Zn-cataly
- Yuan, Yang,Tan, Hailu,Kong, Lingkai,Zheng, Zhong,Xu, Murong,Huang, Jiaqi,Li, Yanzhong
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p. 2725 - 2733
(2019/03/12)
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- Iron-Catalyzed Coupling of Propargyl Bromides and Alkyl Grignard Reagents
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An iron-catalyzed Kumada-type cross-coupling reaction of propargyl halides with alkylmagnesium reagents is described. The reaction is fast, takes place in smooth conditions, tolerates several functional groups that would be able to react with the Grignard reagent, and may afford either allene or propargyl coupling derivatives. Factors involved in the observed regioselectivity have been studied.
- Domingo-Legarda, Pablo,Soler-Yanes, Rita,Quirós-López, M. Teresa,Bu?uel, Elena,Cárdenas, Diego J.
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supporting information
p. 4900 - 4904
(2018/09/10)
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- Lewis-base-catalysed selective reductions of ynones with a mild hydride donor
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Ynones are efficiently reduced with a mild hydride donor in the presence of a catalytic amount of nucleophilic phosphines. The reactions are selective 1,2-reductions that give propargyl alcohols in yields of up to 96%. It is proposed that success in these reactions depends on the activation of ynones by a Lewis base catalyst. A protic additive plays a key role in suppressing the undesired reaction pathways and accelerating the 1,2-reductions.
- Sch?mberg,Zi,Vilotijevic
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p. 3266 - 3269
(2018/04/05)
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- NiICatalyzes the Regioselective Cross-Coupling of Alkylzinc Halides and Propargyl Bromides to Allenes
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We describe the unprecedented formation of allenes by Ni-catalyzed cross-coupling of propargyl bromides with alkylzinc halides. The reaction regioselectivity is complementary to the previously reported formation of propargyl-coupled compounds. Experiments
- Soler-Yanes, Rita,Arribas-álvarez, Iván,Guisán-Ceinos, Manuel,Bu?uel, Elena,Cárdenas, Diego J.
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supporting information
p. 1584 - 1590
(2017/02/10)
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- On the Distribution of Linear versus Angular Naphthalenes in Aromatic Tetradehydro-Diels–Alder Reactions – Effect of Linker Structure and Steric Bulk
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We report here a systematic study of the aromatic tetradehydro-Diels–Alder (Ar-TDDA) reaction to elucidate the factors that have significant effects on the distribution of linear and angular naphthalene products. Two factors were studied, that is, the nat
- Chinta, Bhavani Shankar,Baire, Beeraiah
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supporting information
p. 3381 - 3385
(2017/06/29)
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- Gold-catalyzed Fluorination of Alkynyl Esters and Ketones: Efficient Access to Fluorinated 1,3-Dicarbonyl Compounds
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We developed an efficient synthesis of 2-fluoro-1,3-dicarbonyl compounds using readily available alkynyl ketones or esters as starting material. The key step is the insertion of hydrogen fluoride (HF) to the gold carbene intermediate generated from cationic gold catalyzed addition of N-oxides to alkynyl ketones or esters. This method gives excellent chemical yields and regioselectivity with good functional group tolerance. (Figure presented.).
- Zeng, Xiaojun,Lu, Zhichao,Liu, Shiwen,Hammond, Gerald B.,Xu, Bo
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supporting information
p. 4062 - 4066
(2017/11/30)
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- Asymmetric addition of phenylacetylene to aldehydes catalyzed by complex of O-sulfonyl camphor derivatives and titanium
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Several novel ligands that are based on the camphor skeleton or contain the O-sulfonyl group were synthesized and used in the asymmetric addition of phenylacetylene to aldehydes. This enantioselective reaction afforded chiral propargylic alcohols in high
- Lee, Dong-Sheng,Gau, Chang-Weu,Chen, Yu-Yang,Lu, Ta-Jung
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p. 242 - 246
(2016/04/05)
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- Torquoselectivity in the nazarov reactions of allenyl vinyl ketones
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Nazarov reactions mediated by BF3-etherate of a series of carbon-substituted allenyl vinyl ketones provided intermediates in which substituents on the termini of the allenes had rotated away from the vinyl moieties, and these intermediates were
- Morgan, Timothy D. R.,Leblanc, Luc M.,Ardagh, Giselle H.,Boyd, Russell J.,Burnell, D. Jean
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p. 1042 - 1051
(2015/01/30)
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- Gold-catalyzed oxidative reactions of propargylic carbonates involving 1,2-carbonate migration: Stereoselective synthesis of functionalized alkenes
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A gold-catalyzed oxidative reaction of propargylic carbonates or acetates using 3,5-dichloropyridine as the oxidant has been developed. The reaction provides efficient access to α-functionalized-α,β-unsaturated ketones with excellent regio- and diastereoc
- Sun, Ning,Chen, Ming,Liu, Yuanhong
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p. 4055 - 4067
(2014/05/20)
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- Camphor-based Schiff base ligand SBAIB: An enantioselective catalyst for addition of phenylacetylene to aldehydes
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A series of Schiff base ligands were synthesized from (1R)-camphor. Under the optimal conditions, (+)-SBAIB-a, 10 was found to be an excellent catalyst for the enantioselective addition of phenylacetylene to various aldehydes without utilizing either achiral additives or Ti(OiPr)4. This approach yielded (R)-propargylic alcohols in extremely high yields (up to 99%) and excellent enantioselectivities (up to 92%). The corresponding (S)-propargylic alcohols were synthesized in good to high enantioselectivities (up to 91%) and excellent yields (up to 99%) using (-)-SBAIB-a, 41.
- Boobalan, Ramalingam,Chen, Chinpiao,Lee, Gene-Hsian
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experimental part
p. 1625 - 1638
(2012/03/22)
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- Enantioselective alkynylation of aromatic aldehydes: Pyridyl phenylene terpeneol catalysts with flexible biaryl axes
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Free rotating biaryl axes of pyridyl phenylene terpenols are fixed by zinc cations to give conformationally pure zinc complexes. These zinc alkoxide catalysts provide yields up to 99% and ee values up to 86% in the enantioselective addition of phenylacety
- Leven, Matthias,Müller, David,Goldfuss, Bernd
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experimental part
p. 2505 - 2508
(2011/12/02)
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- Reactivity pattern of bis(propargyloxy) disulfides: Tandem rearrangements and cyclizations
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Thirty-five substituted bis(propargyloxy) disulfides were successfully prepared in good to excellent yields, and their reactivity was found to be strongly dependent on the substitution pattern of the reactant. Inter alia they undergo surprising tandem sigmatropic rearrangements and cycloadditions. Three heretofore unknown product types were isolated and fully characterized: 6,7-dithiabicyclo[3.1.1]heptan-2-one 6-oxide derivatives, two isomeric 1,2-dithiete 1,1-dioxides (α,β-unsaturated four-membered cyclic thiosulfonates) from bis(propargyloxy) disulfides with α- or γ-alkyl-substituted propargyl groups, and two isomeric 2-oxa-5,7-dithiabicyclo[2.2.1]heptane 5-oxides from bis(propargyloxy) disulfides with α-tert-butyl- or α,α-dialkyl-substituted propargyl groups. Georg Thieme Verlag Stuttgart - New York.
- Braverman, Samuel,Pechenick-Azizi, Tatiana,Gottlieb, Hugo E.,Sprecher, Milon
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experimental part
p. 1741 - 1750
(2011/07/09)
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- PtI2-Catalyzed tandem 3,3-rearrangement/Nazarov reaction of arylpropargylic esters: Synthesis of indanone derivatives
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An efficient PtI2-catalyzed tandem reaction of arylpropargylic esters, involving 3,3-rearrangement and Nazarov reaction, has been developed to produce 3-substituted and 3,3-disubstituted indanone derivatives. This approach provided a pathway to the synthesis of indanone skeletons in natural products.
- Zheng, Huaiji,Xie, Xingang,Yang, Juan,Zhao, Changgui,Jing, Peng,Fang, Bowen,She, Xuegong
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experimental part
p. 7755 - 7762
(2011/12/03)
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- Chemoselective addition of in situ prepared lithium alkynyl borates to aldehydes: a practical and transition metal free approach toward the synthesis of propargylic alcohols
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A convenient synthesis of functionalized propargylic alcohols arising from the 1,2-addition of lithium alkynyl-trimethyl borate onto aldehydes under transition metal free mild conditions is reported. The reaction tolerates a wide range of functional groups, is highly chemoselective and the propargylic alcohols are isolated in good to excellent yields.
- Francesco, Irene Notar,Renier, Antoine,Wagner, Alain,Colobert, Fran?oise
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experimental part
p. 1386 - 1389
(2010/04/25)
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- Mild and expedient asymmetric reductions of α,β-unsaturated alkenyl and alkynyl ketones by TarB-NO2 and mechanistic investigations of ketone reduction
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A facile and mild reduction procedure is reported for the preparation of chiral allylic and propargyl alcohols in high enantiomeric purity. Under optimized conditions, alkynyl and alkenyl ketones were reduced by TarB-NO 2 and NaBH4 at 25 °C in 1 h to produce chiral propargyl and allylic alcohols with enantiomeric excesses and yields up to 99%. In the case of α,β-unsaturated alkenyl ketones, α-substituted cycloalkenones were reduced with up to 99% ee, while more substituted and acyclic derivatives exhibited lower induction. For α,β-ynones, it was found that highly branched aliphatic ynones were reduced with optimal induction up to 90% ee, while reduction of aromatic and linear aliphatic derivatives resulted in more modest enantioselectivity. Using the (l)-TarB-NO2 reagent derived from (l)-tartaric acid, we routinely obtained highly enantioenriched chiral allylic and propargyl alcohols with (R) configuration. Since previous models and a reduction of a saturated analogue predicted propargyl products of (S) configuration, a series of new mechanistic studies were conducted to determine the likely orientation of aromatic, alkenyl, and alkynyl ketones in the transition state.
- Eagon, Scott,Delieto, Cassandra,McDonald, William J.,Haddenham, Dustin,Saavedra, Jaime,Kim, Jinsoo,Singaram, Bakthan
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experimental part
p. 7717 - 7725
(2011/01/05)
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- Synthesis of new β-hydroxy amide ligands and their Ti(IV) complex-catalyzed enantioselective alkynylation of aliphatic and vinyl aldehydes
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Three new chiral β-hydroxy amide ligands were synthesized via the reaction of benzyl chloride and amino alcohols derived from l-tyrosine. The titanium(IV) complex of chiral ligand 8b was found to be an effective catalyst for the asymmetric alkynylation of aliphatic, vinyl and aromatic aldehydes. The propargyl alcohols were obtained in highly enantiomeric excesses (up to 96% ee) under optimized conditions.
- Li, Ya-Min,Tang, Yi-Quan,Hui, Xin-Ping,Huang, Lu-Ning,Xu, Peng-Fei
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experimental part
p. 3611 - 3614
(2009/09/06)
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- Cationic rhodium(I)/bisphosphane complex-catalyzed isomerization of secondary propargylic alcohols to α,β-enones
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We have determined that hydrogenated cationic Rh(I)/bisphosphane complexes are highly active catalysts for the isomerization of secondary propargylic alcohols to α,β-enones. A kinetic resolution of secondary propargylic alcohols proceeded with moderate selectivity with [Rh((R)-BINA-P)]OTf as a catalyst. Mechanistic studies revealed that the isomerization proceeds through intramolecular 1,3- and 1,2-hydrogen migration pathways. The isomerization of propargylic diol derivatives was also investigated, which revealed that 1,4-diketones, furans, and α,β-enones were obtained from 2-butyn-1,4-diol, 1-methoxy-2-butyn-4-ol, and 1-acetoxy-2-butyn-4-ol derivatives, respectively. Furthermore, chemoselectivity of the isomerization of an acetylenic diol was investigated, and preferential oxidation of a propargylic hydroxy group was observed. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Tanaka, Ken,Shoji, Takeaki,Hirano, Masao
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p. 2687 - 2699
(2008/02/08)
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- On the viability of 5-endo-dig cyclisations of O-propargylic hydroxylamine derivatives, leading to 2,5-dihydroisoxazoles (3-isoxazolines)
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O-Propargylic hydroxylamines undergo smooth 5-endo-dig cyclisations upon exposure to 3 equiv of molecular iodine to give respectable yields of the corresponding 4-iodo-2,5-dihydroisoxazoles, which should find a number of applications as intermediates for syntheses amongst this useful class of heterocycles.
- Foot, Oliver F.,Knight, David W.,Low, Ai Cheng Lilian,Li, YingFa
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p. 647 - 650
(2007/10/03)
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- Kinetic resolution of propargylic alcohols catalyzed by benzotetramisole
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(Chemical Equation Presented) Kinetic resolution of variously substituted secondary propargylic alcohols catalyzed by benzotetramisole (BTM) proceeds with selectivity factors up to 32, the highest ever achieved with nonenzymatic catalysts for this class o
- Birman, Vladimir B.,Guo, Lei
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p. 4859 - 4861
(2007/10/03)
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- Bisoxazolidine-catalyzed enantioselective alkynylation of aldehydes
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A C2-symmetric bisoxazolidine derived from aminoindanol has been successfully applied in the asymmetric alkynylation of aldehydes. The ligand is readily available, has a wide substrate scope, and catalyzes the formation of chiral propargylic alcohols with excellent yields and enantioselectivties. Copyright
- Wolf, Christian,Liu, Shuanglong
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p. 10996 - 10997
(2007/10/03)
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- Carbohydrate-derived amino-alcohol ligands for asymmetric alkynylation of aldehydes
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Conformationally restricted amino alcohols based on carbohydrate scaffolds provide flexible and fine-tuneable libraries that greatly expand the range of ligands available in the Zn(OTf)2-mediated addition of alkynes to aldehydes, in some cases with very high stereoselectivities.
- Emmerson, Daniel P. G.,Hems, William P.,Davis, Benjamin G.
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p. 207 - 210
(2007/10/03)
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- Lewis base-catalyzed alkynylation of carbonyl compounds with trimethylsilylacetylenes
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Alkynylation of carbonyl compounds with trimethylsilylacetylenes in the presence of a catalytic amount of Lewis bases such as acetate or phenoxide anion is described. The alkynylation proceeded under mild conditions and afforded the corresponding propargyl alcohols in good to excellent yields. Copyright
- Kitazawa, Takayuki,Minowa, Tomofumi,Mukaiyama, Teruaki
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p. 1002 - 1003
(2007/10/03)
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- Cationic rhodium(I)/BINAP complex-catalyzed isomerization of secondary propargylic alcohols to α,β-enones
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(Chemical Equation Presented) We have developed a cationic rhodium(I)/BINAP complex-catalyzed isomerization of secondary propargylic alcohols to α,β-enones. The asymmetric variant of this reaction, a kinetic resolution of secondary propargylic alcohols, was also developed with good selectivity. The mechanistic study revealed that the isomerization proceeds through intramolecular 1,3- and 1,2-hydrogen migration pathways.
- Tanaka, Ken,Shoji, Takeaki
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p. 3561 - 3563
(2007/10/03)
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- Organocatalytic alkynylation of aldehydes and ketones under phase-transfer catalytic conditions
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We developed alkynylations of various aldehydes and ketones under practical phase-transfer conditions at room temperature. The straightforward methodology combines one-pot synthesis and simple workup with good to excellent yields for propargylic alcohols derived from aliphatic aldehydes and ketones. Even aromatic aldehydes and ketones, could be transformed to the corresponding propargylic alcohols in somewhat lower yields. The yield depending on the amount of PT catalyst and NaOH concentration was also determined. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).
- Weil, Torsten,Schreiner, Peter R.
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p. 2213 - 2217
(2007/10/03)
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- Facile and convenient synthesis of functionalized propargylic alcohols and amines: An InBr3-Et3N reagent system promotes the alkynylation of aldehydes and N,O- or N,S-acetals
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The use of a novel InBr3-Et3N reagent system to promote the alkynylation of not only a variety of aromatic/heterocyclic or bulky aliphatic aldehydes but also N,O- or N,S-acetals is described. The use of N-silyl-N,O-acetals and 1-alkynes could lead to the direct production of primary propargylic amines in good yields.
- Sakai, Norio,Kanada, Reiko,Hirasawa, Maki,Konakahara, Takeo
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p. 9298 - 9304
(2007/10/03)
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- Enantioselective alkynylations of aromatic and aliphatic aldehydes catalyzed by terpene derived chiral amino alcohols
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Enantioselective alkynyl zinc additions to aromatic and aliphatic aldehydes have been studied using terpene derived chiral amino alcohol ligands. The limonene derived amino alcohol (1R,2R,5S)-2-methyl-5-(1-methylethenyl)-2-(1- pyrrolidinyl)cyclohexanol ga
- Watts, Cian Christopher,Thoniyot, Praveen,Hirayama, Lacie C.,Romano, Talia,Singaram, Bakthan
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p. 1829 - 1835
(2007/10/03)
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- Asymmetric dihydroxylation of disubstituted allenes
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Asymmetric dihydroxylation of 1,1-disubstituted and 1,3-disubstituted allenes can be used to synthesize chiral α-hydroxy ketones. We have also obtained α,α′-dihydroxy ketones with high enantioselectivity from 1,3-disubstituted allenes. Low conversion of the dihydroxylation of chiral allenes can be used as a kinetic resolution of sterically hindered allenes.
- Fleming, Steven A.,Liu, Renmao,Redd, J. Ty
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p. 8095 - 8098
(2007/10/03)
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- Functionalization of alkynes catalyzed by t-Bu-P4 base
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The addition of O- and N-nucleophiles to alkynes catalyzed by a phosphazene base, t-Bu-P4 base, was investigated. Alkynes were easily transformed to enol ethers and enamines in DMSO by the addition of nucleophiles. When phenylacetylene was reacted with di
- Imahori, Tatsushi,Hori, Chieko,Kondo, Yoshinori
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p. 1090 - 1092
(2007/10/03)
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- Design of small molecule ketoamide-based inhibitors of cathepsin K
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A novel series of ketoamide-based inhibitors of cathepsin K has been identified. Modifications to P2 and P3 elements were crucial to enhancing inhibitory activity. Although not optimized, a selected inhibitor was effective in attenua
- Catalano, John G.,Deaton, David N.,Long, Stacey T.,McFadyen, Robert B.,Miller, Larry R.,Payne, J. Alan,Wells-Knecht, Kevin J.,Wright, Lois L.
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p. 719 - 722
(2007/10/03)
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- Catalytic alkynylation of ketones and aldehydes using quaternary ammonium hydroxide base
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Catalytic alkynylation of diverse ketones and aldehydes using nonmetallic benzyltrimethylammonium hydroxide or a basic resin of the hydroxide type in DMSO is described. Aliphatic or alicyclic carbonyl partners gave satisfactory results, whereas aromatic o
- Ishikawa, Teruhiko,Mizuta, Tomohiro,Hagiwara, Kumiko,Aikawa, Toshiaki,Kudo, Takayuki,Saito, Seiki
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p. 3702 - 3705
(2007/10/03)
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- InBr3-Et3N promoted alkynylation of aldehydes and N,O-acetals under mild conditions: Facile and simple preparation of propargylic alcohols and amines
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The use of a novel InBr3-Et3N reagent system to promote addition reactions of 1-alkynes not only with a variety of aromatic or bulky aliphatic aldehydes but also with N,O-acetals is described. The corresponding propargylic alcohols or amines are produced in good to excellent yields.
- Sakai, Norio,Hirasawa, Maki,Konakahara, Takeo
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p. 4171 - 4174
(2007/10/03)
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- Efficient enantioselective additions of terminal alkynes and aldehydes under operationally convenient conditions
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(Matrix presented) The enantioselective addition reaction of terminal acetylenes and aldehydes mediated by Zn(OTf)2 and N-methyl ephedrine can be conducted with reagent grade solvent containing 84-1000 ppm H2O. The products can be is
- Boyall, Dean,Frantz, Doug E.,Carreira, Erick M.
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p. 2605 - 2606
(2007/10/03)
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- Zn(ODf)2: Preparation and application in asymmetric alkynylation of aldehydes
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A new Lewis acid, Zn(ODf)2, was first prepared from commercially available 3,3,4,4-tetrafluoro[1,2]oxathietane 2,2-dioxide in four steps with 56% yields and also was applied to catalyze highly enantioselective alkynylation of aldehydes in the presence of ligand (1S,2S)-3-(tert-butyldimethylsilyloxyl)-2-N,N-dimethylamino-1-(p- nitrophenyl)-propane-1-ol or ligand (-)-N-methylephedrine to afford the corresponding propargylic alcohols in high yields with up to 99% ee.
- Chen, Zili,Xiong, Wennan,Jiang, Biao
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p. 2098 - 2099
(2007/10/03)
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- Cesium hydroxide: A superior base for the catalytic alkynylation of aldehydes and ketones and catalytic alkenylation of nitriles
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The efficient addition of terminal alkynes to aldehydes or ketones to give propargyl alcohols in yields of 66-96% can be achieved by activation with catalytic amounts of CsOH · H2O [Eq.(a)]. A CsOH-catalyzed addition of acetonitrile derivatives
- Tzalis, Dimitrios,Knochel, Paul
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p. 1463 - 1465
(2007/10/03)
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- LICKOR-Promoted 1,2-elimination in 1,1-dimethoxy-2-phenylethane and 1,1-dimethoxy-2-phenylpropane: synthesis of substituted enol ethers and alkynes
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Dimethyl acetals of phenylacetaldehyde 1a and 2-phenylpropionaldehyde 1b, upon treatment with 1.25 equiv. of LICKOR reagent, undergo 1,2-elimination (THF at -95 deg C) promoted by metallation at the benzylic site, and afford the corresponding enol ethers in the E-form.When the substrate is treated with excess of the base (2.5 equiv.), further hydrogen-metal exchange takes place at the α-vinyl site of the elimination product, and carbonyl electrophiles can be added to the carbanionic intermediate yielding allyl alcohols.Experimental procedures are given for the conversion of the α-substituted derivatives into carbonyl compounds, according to an inverse polarity approach.Moreover, allyl alcohols synthesized starting from 1a, can be transformed into prop-2-ynyl alcohols by treatment with LICKOR base.
- Deagostino, Annamaria,Mella, Mariella,Prandi, Cristina,Venturello, Paolo
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p. 2757 - 2760
(2007/10/02)
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- A straightforward, efficient and versatile preparation of propargylic alcohols from 1-alkynes and aldehydes via GaI3 and amine
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The straightforward additions of 1-alkynes to aldehydes in the presence of GaI3 and an amine give propargylic alcohol in moderate to high yields.
- Han,Huang
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p. 7277 - 7280
(2007/10/02)
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- Chiral Synthesis via Organoboranes. 34. Selective Reductions. 47. Asymmetric Reduction of Hindered α,β-Acetylenic Ketones with B-Chlorodiisopinocampheylborane to Propargylic Alcohols of Very High Enantiomeric Excess. Improved Workup Procedure for the Isol
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The Midland reagent, Alpine-Borane (2a), is excellent for the asymmetric reduction of many acetylenic ketones but it fails with hindered derivatives.On the other hand, B-chlorodiisopinocampheylborane (DIP-Chloride, 4) reacts with hindered α,β-acetylenic k
- Ramachandran, P. Veeraraghavan,Teodorovic, Aleksandar V.,Rangaishenvi, Milind V.,Brown, Herbert C.
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p. 2379 - 2386
(2007/10/02)
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- Sn(OTf)2-Promoted Addition of 1-Alkynes to Aldehydes
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1-Alkynes add to aldehydes and ketones in the presence of Sn(OTf)2 and an amine giving acetylenic alcohols in high yields.
- Yamaguchi, Masahiko,Hayashi, Akio,Minami, Toru
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p. 4091 - 4092
(2007/10/02)
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- AN EFFICIENT SYNTHESIS OF α-F-ALKYNYLATED ALCOHOLS BY NEW SILOXANE-FLUORIDE ION CATALYZED REACTION OF 1H-F-1-ALKENEPHOSPHONATES WITH ALDEHYDES
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1H-F-1-Alkenephosphonates react smoothly with a variety of aldehydes under the influence of catalytic amounts of hexamethyldisiloxane and tetrabutylammonium fluoride at room temperature to afford the corresponding α-F-alkynylated alcohols in good to excel
- Ishihara, Takashi,Maekawa, Takashige,Ando, Teiichi
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p. 357 - 360
(2007/10/02)
-