- Iron-catalysed 1,2-aryl migration of tertiary azides
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1,2-Aryl migration of α,α-diaryl tertiary azides was achieved by using the catalytic system of FeCl2/N-heterocyclic carbene (NHC) SIPr·HCl. The reaction generated aniline products in good yields after one-pot reduction of the migration-resultant imines.
- Wei, Kaijie,Yang, Tonghao,Chen, Qing,Liang, Siyu,Yu, Wei
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supporting information
p. 11685 - 11688
(2020/10/19)
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- Toward the development of efficient and stable Pd-catalysts for the methoxycarbonylation of medium chain alkenes
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Methoxycarbonylation provides a one-step synthesis to valuable ester products utilised in both the fine and heavy chemical industry. However, in general, reaction rates for longer chain alkenes are poor which renders industrial implementation economical unviable. In cases where suitable rates are achieved, the requisite reagents are costly and in addition, the catalyst complexes readily decompose at elevated temperatures. This paper describes the use of an alternative ligand structural motif for the efficient methoxycarbonylation of terminal and internal medium chain alkenes to their corresponding esters. Promising results were obtained using a catalyst complex generated in situ from an unsymmetrical diphosphine ligand based on a ferrocene backbone, Pd(OAc)2 and methane sulfonic acid.
- Bredenkamp, Tyler,Holzapfel, Cedric
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p. 421 - 427
(2016/01/27)
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- Three step auto-tandem catalysed hydroesterification: Access to linear fruity esters from piperylene
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A convenient and selective access to saturated hexanoic esters via hydroesterification of piperylene with synthesis gas and methanol is presented. This is the first three step auto-tandem hydroesterification, which is 100% atom economic proceeding under mild conditions. Our optimisations revealed Pd2(dba)3/1,2-dtbpmb as the best catalytic system. Besides, the reaction also tolerates several alcohols, which offers a broad range of fruity esters. In addition, we present insights into the reaction sequence, investigating whether the reaction proceeds via two- or three-step reaction cascade.
- Neubert, Peter,Steffen, Matthias,Behr, Arno
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p. 122 - 127
(2015/07/15)
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- Silver-mediated oxidative aliphatic C-H trifluoromethylthiolation
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The first example of a practical and direct trifluoromethylthiolation reaction of unactivated aliphatic C-H bonds employs a silver-based reagent. The reaction is operationally simple, scalable, and proceeds under aqueous conditions in air. Furthermore, its broad scope and good functional-group compatibility were demonstrated by applying this method to the selective trifluoromethylthiolation of natural products and natural-product derivatives.
- Guo, Shuo,Zhang, Xiaofei,Tang, Pingping
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supporting information
p. 4065 - 4069
(2015/03/30)
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- Amino acid motifs in natural products: Synthesis of O-acylated derivatives of (2S,3S)-3-hydroxyleucine
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(2S,3S)-3-Hydroxyleucine can be found in an increasing number of bioactive natural products. Within the context of our work regarding the total synthesis of muraymycin nucleoside antibiotics, we have developed a synthetic approach towards (2S,3S)-3- hydroxyleucine building blocks. Application of different protecting group patterns led to building blocks suitable for C- or N-terminal derivatization as well as for solid-phase peptide synthesis. With respect to according motifs occurring in natural products, we have converted these building blocks into 3-O-acylated structures. Utilizing an esterification and cross-metathesis protocol, (2S,3S)-3-hydroxyleucine derivatives were synthesized, thus opening up an excellent approach for the synthesis of bioactive natural products and derivatives thereof for structure activity relationship (SAR) studies.
- Ries, Oliver,Bueschleb, Martin,Granitzka, Markus,Stalke, Dietmar,Ducho, Christian
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supporting information
p. 1135 - 1142
(2014/06/09)
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- Efficient three-step sequence for the deamination of α-aminoesters. Application to the synthesis of CysLT1 antagonists
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A practical and efficient three-step sequence for the deamination of α-aminoesters is reported. This method is based on the NaBH4-mediated selective reduction of α-diazoesters to α-hydrazonoesters and has been successfully applied to the deamin
- González, Alfredo,Pérez, Daniel,Puig, Carles,Ryder, Hamish,Sanahuja, Jordi,Solé, Laia,Bach, Jordi
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supporting information; experimental part
p. 2750 - 2753
(2009/09/25)
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- Functionalization of carboxylic anhydrides at α-carbon with hypervalent iodine reagents: One-pot conversion of anhydrides to 2-sulfonyloxycarboxylate esters
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The treatment of carboxylic anhydrides with iodine(III) sulfonate reagents at ca. 100°C and esterification of the reaction mixtures with MeOH/TsOH·H2O affords 2-sulfonyloxycarboxylate esters. This is consistent with enolic behavior in the anhyd
- Goff, Jeffrey M.,Justik, Michael W.,Koser, Gerald F.
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p. 5597 - 5599
(2007/10/03)
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- IMPROVED SYNTHESIS OF ALIPHATIC KETONES BY THE REACTION OF ALKYLMERCURIC BROMIDES WITH NICKEL CARBONYL IN THE PRESENCE OF POTASSIUM IODIDE
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An improved and convenient procedure for symmetrical aliphatic ketone synthesis is described, which employs the reaction of alkylmercuric bromides with nickel carbonyl in the presence of potassium iodide.
- Ryu, Ilhyong,Ryang, Membo,Rhee, Ilsong,Omura, Haruo,Murai, Shinji,Sonoda, Noboru
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p. 1175 - 1180
(2007/10/02)
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- Synthetic applications of α-hydroxydiazenes. III. Uncatalyzed and phenol catalyzed hydroalkylation of alkenes and of azobenzene with alkylazodiphenylmethanols
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Alkylazodiphenylmethanols (C6H5)2C(OH)N=NR, (R = CH(CH3)2, CH2CH3, CH3), when decomposed in the presence of olefinic substrates or in the presence of azobenzene, hydroalkylate those substrates.Addition of R and H across the double bond of an unsymmetric alkene occurs with the regiochemistry expected for a radical mechanism, in which the grooup R adds first.Radical intermediates from decomposition of alkylazodiphenylmethanols have been demonstrated earlier with spin trapping experiments.The fact that addition of phenol can enhance the yield of hydroalkylation product suggests that the process is a radical chain reaction, with chain carrying steps consisting of the reactions: (i) R. + CH2=CHY -> RCH2C.HY (ii) RCH2C.HY + (C6H5)2C(OH)N2R -> RCH2CH2Y + (C6H5)2CO + N2 + R..One deuterioalkylation and some yield-optimizing experiments are also reported.
- Yeung, Dominic W. K.,Warkentin, John
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p. 2386 - 2394
(2007/10/02)
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- The Reactivity of Carbenes from Photolysis of Diazo-Compounds towards Carbon-Hydrogen Bonds. Effects of Structure, Temperature, and Matrix on the Insertion Selectivity
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Direct and/or sensitized photolyses of diazo-acetate (1a) and -malonate (1b) in hydrocarbons and ether were investigated at various temperatures in order to learn more about the nature of the C-H insertion process and the structural factors governing positional selectivity within the matrix.Photolysis of the diazo-compounds in a rigid matrix resulted in a marked decrease in the insertion selectivity, which may be interpreted as indicating that the matrix imposes severe steric demand especially on the direct C-H insertion process of the singlet carbene.The addition of a sensitizer in matrix photolysis causes a marked increase in the selectivity in the case of (1a), as is observed in the comparable liquid-phase experiment, but it causes a decrease in the case of (1b).This is interpreted as suggesting that the excited triplet (1b) itself is involved in C-H insertion under these conditions.More extensive temperature studies show that, as the temperature decreases, the C-H insertion selectivity of :CHCO2R decreases regularly regardless of the reaction phase, whereas that of :C(CO2R)2 increases in the liquid phase but decreases in the solid phase.This difference in the temperature dependence is explained by assuming that the singlet carbene is responsible for the C-H insertion of :CHCO2R throughout the temperature range studied, while both singlet and triplet are involved in the insertion of :C(CO2R)2.
- Tomioka, Hideo,Itoh, Masami,Yamakawa, Shyoji,Izawa, Yasuji
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p. 603 - 609
(2007/10/02)
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