- Halogen-Substituted Allenyl Ketones through Ring Opening of Nonstrained Cycloalkanols
-
An efficient synthesis of halogen-substituted allenyl ketones via Ag-catalyzed oxidative ring opening of allenyl cyclic alcohols under mild reaction conditions has been achieved. The reaction features a wide substrate scope and excellent regioselectivity. The synthetic potential of the products has been demonstrated by their conversion to stereodefined alkenes and heterocyclic compounds.
- Wu, Penglin,Ma, Shengming
-
supporting information
p. 2533 - 2537
(2021/04/13)
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- Fluorocyclization of Allyl Alcohols and Amines to Access 3-Functionalized Oxetanes and Azetidines
-
An efficient method to prepare 3-functionalized oxetanes and azetidines has been realized by fluorocyclization of readily available 2-azidoallyl/2-alkoxyallyl alcohols and amines. Notably, this is the first example applying the fluorocyclization strategy to construct four-membered heterocycles. The pendant electron-donating group (-N3 or -OR) plays a crucial role in polarizing the C= C double bond and facilitating the cyclization process, as verified by DFT and experimental studies.
- Cao, Shanshan,Li, Linxuan,Liu, Zhaohong,Ning, Yongquan,Wu, Yong,Zanoni, Giuseppe,Zhang, Qi,Zhang, Xinyu
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supporting information
p. 3674 - 3679
(2021/05/31)
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- Enantio- And Diastereodivergent Construction of 1,3-Nonadjacent Stereocenters Bearing Axial and Central Chirality through Synergistic Pd/Cu Catalysis
-
In contrast to the widely explored methods for the asymmetric synthesis of molecules bearing a single stereocenter or adjacent stereocenters, the concurrent construction of 1,3-stereogenic centers in an enantio- and diastereoselective manner remains a challenge, especially in acyclic systems. Herein, we report an enantio- and diastereodivergent construction of 1,3-nonadjacent stereocenters bearing allenyl axial and central chirality through synergistic Pd/Cu-catalyzed dynamic kinetic asymmetric allenylation with racemic allenylic esters. The protocol is suitable for a wide range of substrates including the challenging allenylic esters with less sterically bulky substituents and provided chiral allenylic products bearing 1,3-nonadjacent stereocenters with high levels of enantio- and diastereoselectivities (up to >20:1 dr and >99% ee). Furthermore, several representative transformations involving axial-to-central chirality transfer were conducted, affording useful structural motifs containing nonadjacent stereocenters in a diastereodivergent manner.
- Huo, Xiaohong,Ma, Shengming,Xiao, Junzhe,Zhang, Jiacheng,Zhang, Wanbin,Zhao, Ling
-
supporting information
p. 12622 - 12632
(2021/08/31)
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- ETHERS AND ESTERS OF 1-SUBSTITUTED CYCLOALKANOLS FOR USE AS AROMA CHEMICALS
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The present invention relates to the use of an ether or an ester of a 1 -substituted cycloalkanol or of mixtures of two or more ethers or esters of 1 -substituted cycloalkanols or of a stereoisomer thereof or of a mixture of two or more stereoisomers thereof as aroma chemicals; to the use thereof for modifying the scent character of a fragranced composition; to an aroma chemical composition containing an ether or an ester of a 1 -substituted cycloalkanol or of mixtures of two or more ethers or esters of 1 -substituted cycloalkanols or of a stereoisomer thereof or of a mixture of two or more stereoisomers thereof; and to a method of preparing a fragranced composition or for modifying the scent character of a fragranced composition. The invention further relates to specific ethers or esters of 1 -substituted cycloalkanols.
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Page/Page column 52
(2020/05/21)
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- Synthesis of Imidazo[1,2-a]pyridines and Imidazo[2,1-b]thiazoles Attached to a Cycloalkyl or Saturated Heterocycle Containing a Tertiary Hydroxy Substitution
-
A new method has been developed for the synthesis of imidazo[1,2-a]pyridines, imidazo[2,1-b]thiazoles, and benzo[d]imidazo[2,1-b]thiazoles attached to a cycloalkyl or saturated heterocycle containing a tertiary hydroxy substitution. Readily available substituted 2-aminopyridines, 2-aminothiazoles, and 2-aminobenzothiazoles were treated with bromohydroxycycloalkyl ethanones to afford the desired products in good yields.
- Chenna Reddy,Patil, Vineetkumar B.,Nawaz Khan, Fazlur Rahman,Saravanan, Vadivelu
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p. 1486 - 1497
(2019/04/04)
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- Neighboring Carbonyl Group Assisted Oxyacetoxylation of Propargylic Carboxylates with Retention of Chirality under Metal Free Condition
-
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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p. 3605 - 3611
(2019/07/04)
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- Oxidative Deprotection of p-Methoxybenzyl Ethers via Metal-Free Photoredox Catalysis
-
An efficient and greener deprotection method for p-methoxybenzyl (PMB) ethers using a metal-free visible light photoredox catalyst and air and ammonium persulfate as the terminal oxidants is presented. Various functional groups and protecting groups were tolerated in the developed method to achieve good to excellent yields in short reaction times. Significantly, the developed method was compatible with PMB ethers derived from primary, secondary, and tertiary alcohols and a gram-scale reaction. Mechanistic studies support a proposed reaction mechanism that involves single electron oxidation of the PMB ether.
- Ahn, Deok Kyun,Kang, Young Woo,Woo, Sang Kook
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p. 3612 - 3623
(2019/03/11)
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- Rhodium-Catalyzed Asymmetric Conjugate Alkynylation/Aldol Cyclization Cascade for the Formation of α-Propargyl-β-hydroxyketones
-
A rhodium-catalyzed conjugate alkynylation/aldol cyclization cascade was developed. Densely functionalized cyclic α-propargyl-β-hydroxyketones were synthesized with simultaneous formation of a C(sp)-C(sp3) bond, a C(sp3)-C(sp3) bond, as well as three new contiguous stereocenters. The transformation was achieved with excellent enantio- and diastereoselectivities using BINAP as the ligand. The synthetic utility of the newly installed alkynyl moiety was exhibited by subjecting the products to an array of derivatizations.
- Choo, Ken-Loon,Lautens, Mark
-
supporting information
p. 1380 - 1383
(2018/03/09)
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- Base-Catalyzed Borylation/B-O Elimination of Propynols and B2pin2 Delivering Tetrasubstituted Alkenylboronates
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An efficient approach to tetrasubstituted alkenylboronates via a cascade borylation/B-O elimination of propynols and B2pin2 was disclosed. A series of tetrasubstituted alkenylboronates were readily furnished with this strategy in good yields, with further transformations leading to tetrasubstituted alkenes and β-diketones demonstrating the synthetic potential of the alkenylboronates constructed by this strategy as versatile intermediates in organic synthesis.
- Kuang, Zhijie,Chen, Haohua,Yan, Jianxiang,Yang, Kai,Lan, Yu,Song, Qiuling
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supporting information
p. 5153 - 5157
(2018/09/12)
-
- Method for efficiently preparing alkynol
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The invention relates to a method for efficiently preparing alkynol, belongs to the field of preparation of chemical intermediates and chemicals, and particularly relates to a preparation method of alkynol. The preparation method comprises the following steps that 1, alkali metal is added into an anhydrous alcohols solvent; an alcohol-alkali metal solution is prepared; 2, a compound I is added into the alcohol-alkali metal solution; uniform stirring is performed; cooling is performed to be 0 DEG C or below; 3, acetylene is introduced through being metered at normal pressure; alkynol is obtained; 4, the alkynol solution after reaction is neutralized by ammonium chloride and a same alcohol mixed suspension system; 5, the neutralized mixed suspension system is filtered; after alcohols are recovered from filter liquid, reduced pressure distillation is performed to obtain an alkynol product. The method overcomes the defect that under the existing harsh reaction conditions of high pressure,liquid ammonia and the like, the solid potassium hydroxide feeding difficulty is avoided; under the ordinary pressure condition, the ketone compounds are converted into alkynol at high conversion rate. The method has the advantages of high conversion rate, simple process and good product purity.
- -
-
Paragraph 0036; 0037; 0038; 0043; 0044; 0045; 0046
(2018/12/14)
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- Using Calcium Carbide as an Acetylene Source for Cascade Synthesis of Pyrrolo[2,3-b]quinoxalines via Copper-Free Sonogashira Coupling Reaction
-
A palladium-catalyzed cascade protocol has been established for the synthesis of 4-methyl-1-(1H-pyrrolo[2,3-b]-quinoxalin-2-yl)cyclohexanols and 2-phenyl-1-(1H-pyrrolo[2,3-b]quinoxalin-2-yl)propan-1-ols through the reaction of N-alkyl(aryl)-3-chloroquinox
- Fakharian, Mahsa,Keivanloo, Ali,Nabid, Mohammad Reza
-
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- Synthesis of 1,4-Disubstituted 1,2,3-Triazoles via 1,3-Dipolar Cycloaddition/C–N Coupling of Propargyl Alcohols/amines and Aryl Azides
-
1,4-Disubstituted 1,2,3-triazoles are prepared through the 1,3-dipolar cycloaddition of propargyl (alcohols/amines) and aryl azides in the presence of a mixture of Cu(OAc)2.H2O and NaAs as the catalyst. This method offers the advantages of mild experimental conditions, operational simplicity, and high-to-excellent reaction yields.
- Bakherad, Mohammad,Ghalenoei, Ahmad Kakavand,Keivanloo, Ali
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p. 2683 - 2692
(2018/11/10)
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- Synthesis of Vinyl-, Allyl-, and 2-Boryl Allylboronates via a Highly Selective Copper-Catalyzed Borylation of Propargylic Alcohols
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An efficient methodology for the synthesis of vinyl-, allyl-, and (E)-2-boryl allylboronates from propargylic alcohols via Cu-catalyzed borylation under mild conditions is reported. In the presence of commercially available Cu(OAc)2 or Cu(acac)2 and Xantphos, the reaction affords the desired products in up to 92% yield with a broad substrate scope (43 examples). Isolation of an allenyl boronate as the reaction intermediate suggests that an insertion-elimination-type reaction, followed by borylcupration, is involved in the borylation of propargylic alcohols.
- Mao, Lujia,Bertermann, Rüdiger,Emmert, Katharina,Szabó, Kálmán J.,Marder, Todd B.
-
supporting information
p. 6586 - 6589
(2017/12/26)
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- Palladium(II)-Catalyzed Site-Selective C(sp3)?H Alkynylation of Oligopeptides: A Linchpin Approach for Oligopeptide–Drug Conjugation
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The palladium(II)-catalyzed C(sp3)?H alkynylation of oligopeptides was developed with tetrabutylammonium acetate as a key additive. Through molecular design, the acetylene motif served as a linchpin to introduce a broad range of carbonyl-containing pharmacophores onto oligopeptides, thus providing a chemical tool for the synthesis and modification of novel oligopeptide–pharmacophore conjugates by C?H functionalization. Dipeptide conjugates with coprostanol and estradiol were synthesized by this method for potential application in targeted drug delivery to tumor cells with overexpressed nuclear hormone receptors.
- Liu, Tao,Qiao, Jennifer X.,Poss, Michael A.,Yu, Jin-Quan
-
supporting information
p. 10924 - 10927
(2017/08/30)
-
- Copper(I)-catalyzed regio- and stereoselective intramolecular alkylboration of propargyl ethers and amines
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The copper(I)-catalyzed regio- and stereoselective intramolecular alkylation of propargyl ethers and amines bearing an alkyl electrophilic moiety has been developed. The reaction showed high functional group tolerance and gave highly functionalized alkenylboronates bearing heterocyclic rings, which are versatile synthetic intermediates in organic chemistry. The borylation products can be transformed into multisubstituted alkenes through stereospecific transformations. Mechanistic studies showed that the chemo- and stereoselectivity of copper(I)-catalyzed borylation depends on the type of leaving group. Density functional theory calculations suggested that the regioselectivity of the borylcupration of the alkyne is controlled by the electronic effect of the oxygen atom of the propargyl ether in combination with the steric congestion between the boryl group and the substituent at the propargylic position.
- Iwamoto, Hiroaki,Ozawa, Yu,Kubota, Koji,Ito, Hajime
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p. 10563 - 10573
(2018/05/31)
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- Polycyclic bridgehead acetals with enol functionality: one-pot assembly from aliphatic ketones and acetylene in KOH/DMSO suspension
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Aliphatic and cycloaliphatic ketones undergo selective multi-site cascade C–H functionalization with acetylene in the KOH/DMSO superbase suspension under mild conditions (70–80?°C, 0.5–1.0?h) to afford in one synthetic operation polycyclic bridgehead acet
- Schmidt, Elena Yu.,Bidusenko, Ivan A.,Cherimichkina, Natalia A.,Ushakov, Igor A.,Trofimov, Boris A.
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p. 4510 - 4517
(2016/07/07)
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- Gold-catalyzed reactions of propargylic esters with vinylazides for the synthesis of Z- or E-configured buta-1,3-dien-2-yl esters
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Gold-catalyzed synthesis of buta-1,3-dien-2-yl esters by the reaction of propargyl esters with vinylazides is described; the reaction mechanism is postulated to involve a vinyl attack of vinylazides at alkenyl gold carbenes.
- Wagh, Sachin Bhausaheb,Liu, Rai-Shung
-
supporting information
p. 15462 - 15464
(2015/10/20)
-
- Efficient synthesis and antibacterial activities of some novel 1,2,3-triazoles prepared from propargylic alcohols and benzyl azides
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A simple and effective procedure for regioselective preparation of 1,2,3-triazoles from benzyl azides and propargylic alcohols is described using CuSO4·5H2O and sodium ascorbate. To screen the antibacterial activity of some newly synthesized triazole derivatives, minimum inhibitory concentration of 3d and 3k was evaluated against gram positive Staphylococcus aureus and Bacillus subtilis and gram negative Escherichia coli and Pseudomonas aeruginosa.
- Hosseinzadeh, Rahman,Abolfazli, Mohammadreza Khadem,Mohseni, Mojtaba,Mohadjerani, Maryam,Lasemi, Zahra
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p. 1298 - 1305
(2015/04/27)
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- Microwave-Assisted Organocatalyzed Rearrangement of Propargyl Vinyl Ethers to Salicylaldehyde Derivatives: An Experimental and Theoretical Study
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The microwave-assisted imidazole-catalyzed transformation of propargyl vinyl ethers (PVEs) into multisubstituted salicylaldehydes is described. The reaction is instrumentally simple, scalable, and tolerates a diverse degree of substitution at the propargylic position of the starting PVE. The generated salicylaldehyde motifs incorporate a broad range of topologies, spanning from simple aromatic monocycles to complex fused polycyclic systems. The reaction is highly regioselective and takes place under symmetry-breaking conditions. The preparative power of this reaction was demonstrated in the first total synthesis of morintrifolin B, a benzophenone metabolite isolated from the small tree Morinda citrifolia L. A DFT study of the reaction was performed with full agreement between calculated values and experimental results. The theoretically calculated values support a domino mechanism comprising a propargyl Claisen rearrangement, a [1,3]-H shift, a [1,7]-H shift (enolization), a 6π electrocyclization, and an aromatization reaction.
- Tejedor, David,Cotos, Leandro,Márquez-Arce, Daniel,Odriozola-Gimeno, Mikel,Torrent-Sucarrat, Miquel,Cossío, Fernando P.,García-Tellado, Fernando
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supporting information
p. 18280 - 18289
(2015/12/24)
-
- Photoredox removal of p-methoxybenzyl ether protecting group with hydrogen peroxide as terminal oxidant
-
We report a mild protocol for removal of the p-methoxybenzyl ether protecting group under acidic conditions with eosin Y combined with LEDs as a photoredox catalysis system and hydrogen peroxide as the terminal oxidant. This protocol is compatible with ethers derived from primary, secondary, and tertiary alcohols, as well as with various functional groups. The protocol showed unusual selectivity for a tertiary ether over a primary ether. The scale up to gram scale is also explored and identical reactivity is observed.
- Liu, Zheng,Zhang, Yi,Cai, Zheren,Sun, Hao,Cheng, Xu
-
supporting information
p. 589 - 593
(2015/03/05)
-
- Fluoride-assisted activation of calcium carbide: A simple method for the ethynylation of aldehydes and ketones
-
The fluoride-assisted ethynylation of ketones and aldehydes is described using commercially available calcium carbide with typically 5 mol % of TBAF·3H2O as the catalyst in DMSO. Activation of calcium carbide by fluoride is thought to generate an acetylide "ate"-complex that readily adds to carbonyl groups. Aliphatic aldehydes and ketones generally provide high yields, whereas aromatic carbonyls afford propargylic alcohols with moderate to good yields. The use of calcium carbide as a safe acetylide ion source along with economic amounts of TBAF·3H2O make this procedure a cheap and operationally simple method for the preparation of propargylic alcohols.
- Hosseini, Abolfazl,Seidel, Daniel,Miska, Andreas,Schreiner, Peter R.
-
supporting information
p. 2808 - 2811
(2015/06/16)
-
- ZnII- and AuI-catalyzed regioselective hydrative oxidations of 3-En-1-ynes with selectfluor: Realization of 1,4-dioxo and 1,4-oxohydroxy functionalizations
-
Catalytic 1,4-dioxo functionalizations of 3-en-1-ynes to (Z)- and (E)-2-en-1,4-dicarbonyl compounds are described. This regioselective difunctionalization was achieved in one-pot operation through initial alkyne hydration followed by in situ Selectfluor oxidation. The presence of pyridine alters the reaction chemoselectivity to give 4-hydroxy-2-en-1-carbonyl products instead. A cooperative action of pyridine and ZnII assists the hydrolysis of key oxonium intermediate.
- Jadhav, Appaso Mahadev,Gawade, Sagar Ashok,Vasu, Dhananjayan,Dateer, Ramesh B.,Liu, Rai-Shung
-
supporting information
p. 1813 - 1817
(2014/03/21)
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- Alkynylation of aldehydes and ketones using the Bu4NOH/H 2O/DMSO catalytic composition: A wide-scope methodology
-
The Favorsky reaction of a wide range of aldehydes and ketones with alkynes has been implemented under mild conditions (5-20 C). Using a Bu 4NOH/H2O/DMSO catalytic system, propargylic alcohols are formed cleanly in 39-93% (mostly 72-93%) yields and with ca. 100% selectivity. The method is suitable for aliphatic, aromatic, and heteroaromatic aldehydes and ketones, and for aliphatic, aromatic, and functionalized acetylenes. Thus, this represents the most general and efficient protocol to achieve the Favorsky reaction. Copyright
- Schmidt, Elena Yu.,Cherimichkina, Natalia A.,Bidusenko, Ivan A.,Protzuk, Nadezhda I.,Trofimov, Boris A.
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p. 4663 - 4670
(2014/08/05)
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- Facile synthesis of halogenated spiroketals via a tandem iodocyclization
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A strategy for the synthesis of spiroketal compounds through a tandem iodocyclization of 1-(2-ethynylphenyl)-4-hydroxybut-2-yn-1-one derivatives is presented. This reaction could proceed under very mild conditions in a short time and avoid the use of expensive and toxic metal catalysts. Moreover, the resulting halides can be further exploited by subsequent palladium-catalyzed coupling reactions, which act as the important intermediates for building other valuable compounds.
- Wang, Jia,Zhu, Hai-Tao,Li, Ying-Xiu,Wang, Li-Jing,Qiu, Yi-Feng,Qiu, Zi-Hang,Zhong, Mei-Jin,Liu, Xue-Yuan,Liang, Yong-Min
-
supporting information
p. 2236 - 2239
(2014/05/06)
-
- Synthesis of acetylenic alcohols with calcium carbide as the acetylene source
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Propargyl alcohols containing a terminal alkyne group are highly important and versatile intermediates. Here, we report the synthesis of these compounds from an inexpensive and renewable resource, calcium carbide (CaC2). No metal catalysts are required in this new protocol and the reactions take place under very mild conditions.
- Sum, Yin Ngai,Yu, Dingyi,Zhang, Yugen
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supporting information
p. 2718 - 2721
(2013/10/08)
-
- Versatile gold catalyzed transglycosidation at ambient temperature
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Glycosidation with stable alkyl glycosyl donors using a catalytic amount of gold salts is promising. Herein, 1-ethynylcyclohexanyl glycosides are identified as novel donors at room temperature and mechanistic investigation showed that the leaving group simply extrudes out.
- Kayastha, Abhijeet K.,Hotha, Srinivas
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scheme or table
p. 7161 - 7163
(2012/07/31)
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- Gold(i)-catalyzed Claisen rearrangement of allenyl vinyl ethers; Synthesis of substituted 1,3-dienes
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Synthesis of substituted 1,3-dienes was achieved via gold(i)-catalyzed Claisen rearrangement of allenyl vinyl ethers. The N-heterocyclic carbene gold chloride catalyst (IPrAuCl) was superior in terms of activity and selectivity and afforded the 3,3-product in excellent yields. A proposed cation-π inter-action played a significant role in affecting the reaction rate.
- Krafft, Marie E.,Hallal, Kassem M.,Vidhani, Dinesh V.,Cran, John W.
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supporting information; experimental part
p. 7535 - 7538
(2011/12/03)
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- Gold-catalyzed regioselective hydration of propargyl acetates assisted by a neighboring carbonyl group: Access to α-acyloxy methyl ketones and synthesis of (±)-actinopolymorphol B
-
A general atom-economical approach for the synthesis of α-acyloxy methyl ketone is demonstrated through regioselective hydration of a wide range of propargyl acetates. Readily available catalyst comprising of 1% Ph 3PAuCl and 1% AgSbF6 in dioxane-H2O efficiently hydrolyzes the terminal alkynes of the propargyl acetate in the absence of acid promoters at ambient temperature within a short time. Effective regioselective hydration is facilitated by the neighboring carbonyl group as demonstrated through 18O-labeling study. Compatibility of functional moieties and tolerance to various acid-labile protecting groups are observed. The catalytic condition is also suitable to perform hydration of TMS-substituted propargyl acetates, even though it requires prolonged reaction time for completion. Stereointegrity of the propargylic acetate is preserved during the hydration. The robustness of the system is successfully demonstrated through gram scale preparation of the product in nearly quantitative yield. The common α-acyloxy methyl ketone is transformed to 1,2-diol and 1,2-amino alcohol derivatives. Synthesis of actinopolymorphol B is achieved for the first time involving hydration of the propargyl acetate as the key step.
- Ghosh, Nayan,Nayak, Sanatan,Sahoo, Akhila K.
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p. 500 - 511
(2011/04/17)
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- A mild and efficient method for the selective deprotection of silyl ethers using KF in the presence of tetraethylene glycol
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A mild and efficient protocol for the deprotection of silyl ethers using KF in tetraethylene glycol is reported. A wide range of alcoholic silyl ethers can be selectively cleaved in high yield in the presence of certain acid- and base-labile functional groups. Moreover, the phenolic silyl ethers were cleaved exclusively, without affecting the alcoholic silyl ethers, at room temperature. The Royal Society of Chemistry 2011.
- Yan, Hailong,Oh, Joong-Suk,Song, Choong Eui
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supporting information; experimental part
p. 8119 - 8121
(2012/01/04)
-
- A mild method for the deprotection of tetrahydropyranyl (THP) ethers catalyzed by iron(III) tosylate
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A mild method for the deprotection of THP ethers catalyzed by iron(III) tosylate (2.0 mol %) in CH3OH has been developed. Iron(III) tosylate, Fe(OTs)3·6H2O, is a commercially available solid that is inexpensive, noncorrosive, and easy to handle. The room temperature reaction conditions make this method attractive for deprotection of a range of THP ethers.
- Bockman, Matthew R.,Angeles, Veronica V.,Martino, Julia M.,Vagadia, Purav P.,Mohan, Ram S.
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experimental part
p. 6939 - 6941
(2012/02/05)
-
- Stereoselective One-Pot synthesis of 1-Aminoindanes and 5,6-Fused azacycles using a Gold-Catalyzed Redox-Pinacol-Mannich-Michael cascade
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"Chemical Equation Presented" Just another Mannich Monday: A cascade intramolecular redox-pinacol-Mannich-Michael reaction sequence catalyzed by gold complexes can be used to generate a variety of structures including spirocycles, 1-aminoindanes, and 5,6-fused azabicycles that have a quaternary carbon center. The reaction is characterized by complete atom-economy, high diastereoselectivity, and remarkable efficiency through tandem reactions.
- Yeom, Hyun-Suk,Lee, Youngun,Jeong, Jaewon,So, Eunsoo,Hwang, Soojin,Lee, Ji-Eun,Lee, Shim Sung,Shin, Seunghoon
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supporting information; experimental part
p. 1611 - 1614
(2010/06/15)
-
- A tetranuclear-zinc-cluster-catalyzed practical and versatile deprotection of acetates and benzoates
-
A new catalytic deacylation of acetates and benzoates through transesterification with methanol was developed (see scheme). Reactions with various acidand nucleophile-sensitive functional groups proceeded efficiently in the presence of a catalytic amount of the tetranuclear zinc cluster. The present catalysis is applicable to less-reactive tertiary acetates, the deacylation of which is difficult to achieve by transesterification with other catalysts.
- Iwasaki, Takanori,Agura, Kazushi,Maegawa, Yusuke,Hayashi, Yukiko,Ohshima, Takashi,Mashima, Kazushi
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supporting information; experimental part
p. 11567 - 11571
(2010/11/24)
-
- Mo(CO)6-mediated intramolecular pauson-Khand reaction of substituted Diethyl 3-Allyloxy-1-Propynylphosphonates
-
Cyclisation of diethyl 3-allyloxy-1-propynylphosphonates with Mo(CO) 6 under PK conditions to give 3-substituted-5-oxo-3,5,6,6a- tetrahydro-1H-cyclopenta[c]furan-4-ylphosphonate, 2a-h,in45-88% isolated yields was done. The R groups are always syn with Hb (where applicable). The stereochemistry was determined via both NMR and crystal X-ray analysis.
- Moradov, Dorit,Quntar, Abed Al Aziz Al,Youssef, Manar,Smoum, Reem,Rubinstein, Abraham,Srebnik, Morris
-
supporting information; experimental part
p. 1029 - 1033
(2009/08/08)
-
- Efficient synthesis of 3-chloromethyl-2(5H)-furanones and 3-chloromethyl- 5,6-dihydropyran-2-ones via the PdCl2-catalyzed chlorocyclocarbonylation of 2,3- or 3,4-allenols
-
(Chemical Equation Presented) A mild and efficient methodology involving PdCl2-catalyzed chlorocyclocarbonylation of 2,3- or 3,4-allenols with CuCl2 for the synthesis of 3-chloromethyl-2(5H)-furanones and 3-chloromethyl-5,6-dihydropyran-2-ones was developed. This reaction proceeded in a highly regioselective manner, i.e., the chlorine atom was introduced to the terminal position of the allene moiety while the lactone linkage was formed between the center carbon atom of the allene moiety and the hydroxyl oxygen, which was established by the X-ray single crystal diffraction study of γ-lactone 3p. The highly optically active 3-chloromethyl-2(5H)-furanones could be easily prepared from the readily available optically active 2,3-allenols. A mechanism for this reaction was proposed.
- Cheng, Xin,Jiang, Xuefeng,Yu, Yihua,Ma, Shengming
-
scheme or table
p. 8960 - 8965
(2009/04/11)
-
- PHOSPHONIUM IONIC LIQUIDS AS RECYCLABLE SOLVENTS FOR SOLUTION PHASE CHEMISTRY
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This application relates to the use of phosphonium-based ionic liquids as recyclable solvents for solution phase chemistry. The ionic liquids may be used, for example, as solvents for reactions involving Grignard reagents, hydridic reagents, metallic and non-metallic reducing agents, and strong bases, including nucleophilic carbenes and Wittig reagents. In one embodiment the invention may comprise homogeneous mixtures of strong bases/nucleophiles/reducing agents and tetrahydrocarbylphosphonium salt ionic liquids. The invention also relates to chemical processes that may proceed in either minimally flammable solvent, or a complete absence of flammable solvent, including systems containing strong reducing agents such as alkali and alkaline metals or metal and non-metal hydrides. Methods for generating anions and nucleophililic carbenes (imidazol-2-ylidenes) (and complexes derived from them) in phosphonium-based ionic liquids are also described. The invention demonstrates the feasibility of using phosphonium-based ionic liquids as a reliable reaction media for a wide variety of basic reagents. The problems associated with C-H activation in imidazolium-based ionic liquids by highly reactive bases are not observed for phosphonium-based ionic liquids.
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Page/Page column 28
(2010/02/15)
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- Synthesis of alkyne derivatives of a novel triazolopyrazine as A 2A adenosine receptor antagonists
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A novel [1,2,4]triazolo[1,5-a]pyrazine core was synthesized and coupled with terminal acetylenes. The structure-activity relationship of the alkynes from this novel template was studied for their in vitro and in vivo adenosine A2A receptor antagonism. Selected compounds from this series were shown to have potent in vitro and in vivo activities against adenosine A 2A receptor. Compound 12, in particular, was found to be orally active at 3 mg/kg in both a mouse catalepsy model and a 6-hydroxydopamine- lesioned rat model.
- Yao, Gang,Haque, Serajul,Sha, Li,Kumaravel, Gnanasambandam,Wang, Joy,Engber, Thomas M.,Whalley, Eric T.,Conlon, Patrick R.,Chang, Hexi,Kiesman, William F.,Petter, Russell C.
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p. 511 - 515
(2007/10/03)
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- New heterocycles: 4-Methyl-2H-pyrano[6,5-f]cycloalka[2,1-b]2H-chromen-2- ones
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A synthesis of the new heterocycles, 4-methyl-2H-pyrano[6,5-f]cycloalka[2, 1-b]2H-chromen-2-ones (3) was described, via the unexpected intermediates 2-chloro-1-chloroethenylidenecycloalkanes (6) from the reaction of 1-ethynylcycloalkanols with thionyl chloride. The mechanism of some steps was discussed.
- Zhang, Qian,Chen, Ying,Xia, Yi,Yang, Zhengyu,Xia, Peng
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p. 1637 - 1643
(2007/10/03)
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- Effects of Structural Factors in Silyl Ethers Derived from Terminal Acetylenic Alcohols on 1,4-O→Csp Migration of the Silyl Group
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Effects of structural factors in silyl ethers derived from terminal acetylenic alcohols on 1,4-O-→Csp migration of the silyl group in the Iotsitch reagent were studied. The effect of steric factor at the carbon atom neighboring to the reaction center was found to be stronger than that at the silicon atom in the migrating group.
- Medvedeva,Novokshonov,Mareev,Borisova
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p. 336 - 339
(2007/10/03)
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- Bismuth triflate: An efficient catalyst for the formation and deprotection of tetrahydropyranyl ethers
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The tetrahydropyranylation of alcohols under solvent-free conditions is efficiently catalyzed by bismuth triflate (0.1 mol %). The experimental procedure is simple and works well with a variety of alcohols and phenols. The catalyst is insensitive to air and small amounts of moisture, easy to handle and relatively nontoxic. The deprotection of THP ethers is also catalyzed by bismuth triflate (1.0 mol %). ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).
- Stephens, Jacqueline R.,Butler, Phillip L.,Clow, Curtis H.,Oswald, Matthew C.,Smith, Russell C.,Mohan, Ram S.
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p. 3827 - 3831
(2007/10/03)
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- Facile approach to versatile chiral intermediates for fused cyclopentanoid natural products
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A facile approach to cis- and trans-2-(1-hydroxymethyl)vinyl-1-vinylcyclohexan-1-ols and to the corresponding cyclopentane, cycloheptane, and cyclooctane derivatives has been developed, starting from cycloalkanones involving the key steps of Rupe and Claisen orthoester rearrangements. The formation of intervening products could be explained by allylic strain and π-stacking, respectively.
- Zulfiqar, Fazila,Malik, Abdul
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p. 1227 - 1234
(2007/10/03)
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- Mild and selective sodium azide mediated cleavage of p-nitrobenzoic esters.
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[reaction: see text] A mild and selective cleavage of p-nitrobenzoic esters by sodium azide in methanol is reported. This new methodology is mild enough for use with acid- or base-sensitive compounds. No elimination byproducts are formed. Fmoc- and trifluoroacetyl-amino protecting groups, benzyl esters, and ethyl esters remain unaffected. Less reactive compounds are discussed in terms of steric factors, and yields are increased by altering the azide solvation.
- Gomez-Vidal,Forrester,Silverman
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p. 2477 - 2479
(2007/10/03)
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- Carbon-carbon bond formation in regio- and stereoselective palladium-catalyzed cyclization of allene-substituted conjugated dienes
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Regio- and stereoselective palladium-catalyzed reactions of allene-substituted 1,3-dienes 1 in acetic acid at room temperature lead to cyclization with formation of a carbon-carbon bond between the middle carbon of the allene and the terminal carbon of the 1,3-diene. Two different types of reactions, both that constitute 1,4-carboacetoxylations of the 1,3-diene, have been developed. In one of the reactions, Pd(II) catalyzes the oxidation of 1 to bicyclic compounds 2, and in the other, Pd(0) catalyzes the transformation of 1 to bicyclic compounds 3. The products 2 are useful for further synthetic tr0nsformations and undergo Diels-Alder reactions with dienophiles to give polycyclic ring systems.
- Loefstedt, Joakim,Franzen, Johan,Baeckvall, Jan-E.
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p. 8015 - 8025
(2007/10/03)
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- Highly efficient deacetylation by use of the neutral organotin catalyst [tBu2SnOH(Cl)]2
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Deprotection of acetyl esters is effected cleanly by the neutral organotin catalyst, [tBu2SnOH(Cl)]2. The mildness of the reaction gives rise to great synthetic versatility and in the process a variety of functional groups are tolerated. Differentiations between primary, secondary, and tertiary alcohols and between acetyl ester and other esters are feasible. No racemization occurs with chiral acetyl esters. Exclusive deprotection of primary acetyl esters in carbohydrates and nucleosides is observed. The crude product thus obtained can be used for further reactions without purification.
- Orita, Akihiro,Hamada, Yuuki,Nakano, Takehiko,Toyoshima, Shinji,Otera, Junzo
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p. 3321 - 3327
(2007/10/03)
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- Synthesis of C5-substituted AE-bicyclic analogues of lycoctonine, inuline and methyllycaconitine
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We have prepared C5-substituted AE-bicyclic analogues of norditerpenoid alkaloids lycoctonine, inuline and methyllycaconitine via an acetylide anion addition strategy. Using two acetylide anions, we have regioselectively linked two cyclic ketones to acetylene.
- Grangier, Geraldine,Trigg, William J.,Lewis, Terence,Rowan, Michael G.,Potter, Barry V. L.,Blagbrough, Ian S.
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p. 889 - 892
(2007/10/03)
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- Phenol catalyzed Claisen ortho ester rearrangment of allylic alcohols with trimethyl-β-(methoxy) ortho propionate
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Phenol catalyzed Claisen ortho ester rearrangment of allylic alcohols with trimethyl-β-(methoxy) ortho propionate can be affected in relatively quick time and lower temperature with only 1.5 equivalents of ortho ester. The rearrangement does not experience undesirable side reactions reported earlier in literature [3].
- Iqbal, Fazila,Ateeq, Humayun S.,Malik, Abdul,Zeeshan,Ali, Zulfiqar
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p. 1244 - 1245
(2007/10/03)
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- Synthesis and anti-aggregative activity of novel ω-achiral carba-analogues of prostacyclin
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Novel stable bicyclo[3.3.0]octanic and bicyclo[4.2.0]octanic 13,14-didehydrocarbacyclins 1a-c, 2a bearing an achiral cyclohexanoic group at C-14 were synthesized. These analogues have been characterized by 13C NMR spectroscopy. Compounds 1a-c and 2a were tested on rabbit and human platelet-rich blood plasma and 1a-c on rat stomach and guinea pig trachea smooth muscles. E-isomers of 1a-b were found to be less active but more selective than PGE1. The anti-aggregative potency of E-isomer of compounds 1a-b and Z-isomer of 2a on human platelets was 10-1-10-2 of the activity of PGE1. The contractive activity of bicyclo[3.3.0]octane analogues 1a-c was 10-3-10-4 of that for PGE1. On platelets and guinea-pig trachea 5E-isomers of the corresponding analogues were more potent, whereas on rat stomach muscle 5Z-isomers were.
- Lopp,Kobzar,Bergmann,Pehk,Lopp,Valimae,Viigimaa,Lille
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p. 155 - 159
(2007/10/02)
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