42036-73-7Relevant academic research and scientific papers
Selective C-H chalcogenation of thiazoles: Via thiazol-2-yl-phosphonium salts
Zi, You,Wagner, Konrad,Sch?mberg, Fritz,Vilotijevic, Ivan
, p. 5183 - 5191 (2020/07/23)
Thiazoles and benzothiazoles undergo regioselective C2-H chalcogenation via the sequence of thiazole C2-functionalization with phosphines to produce phosphonium salts which in turn react with S- and Se-centered nucleophiles to give products of C2-H chalco
Switch in Selectivity for Formal Hydroalkylation of 1,3-Dienes and Enynes with Simple Hydrazones
Li, Chao-Jun,Lv, Leiyang,Qiu, Zihang,Yu, Lin
supporting information, p. 6466 - 6472 (2020/03/13)
Controlling reaction selectivity is a permanent pursuit for chemists. Regioselective catalysis, which exploits and/or overcomes innate steric and electronic bias to deliver diverse regio-enriched products from the same starting materials, represents a powerful tool for divergent synthesis. Recently, the 1,2-Markovnikov hydroalkylation of 1,3-dienes with simple hydrazones was reported to generate branched allylic compounds when a nickel catalyst was used. As part of the effort, shown here is that a complete switch of Markovnikov to anti-Markovnikov addition is obtained by changing to a ruthenium catalyst, thus providing direct and efficient access to homoallylic products exclusively. Isotopic substitution experiments indicate that no reversible hydro-metallation across the metal-π-allyl system occurred under ruthenium catalysis. Moreover, this protocol is applicable to the regiospecific hydroalkylation of the distal C=C bond of 1,3-enynes.
Energy Transfer from CdS QDs to a Photogenerated Pd Complex Enhances the Rate and Selectivity of a Pd-Photocatalyzed Heck Reaction
Zhang, Zhengyi,Rogers, Cameron R.,Weiss, Emily A.
supporting information, p. 495 - 501 (2020/01/03)
This Article describes the design of a colloidal quantum dot (QD) photosensitizer for the Pd-photocatalyzed Heck coupling of styrene and iodocyclohexane to form 2-cyclohexylstyrene. In the presence of 0.05 mol % CdS QDs, which have an emission spectrum that overlaps the absorption spectrum of a key Pd(II)alkyl iodide intermediate, the reaction proceeds with 82% yield for the Heck product at 0.5 mol % loading of Pd catalyst; no product forms at this loading without a sensitizer. A radical trapping experiment and steady-state and transient optical spectroscopies indicate that the QDs transfer energy to a Pd(II)alkyl iodide intermediate, pushing the reaction toward a Pd(I) alkyl radical species that leads to the Heck coupled product, and suppressing undesired β-hydride elimination directly from the Pd(II)alkyl iodide. Functionalization of the surfaces of the QDs with isonicotinic acid increases the rate constant of this reaction by a factor of 2.4 by colocalizing the QD and the Pd-complex. The modularity and tunability of the QD core and surface make it a convenient and effective chromophore for this alternative mode of cooperative photocatalysis.
Nickel-Catalyzed Alkylation or Reduction of Allylic Alcohols with Alkyl Grignard Reagents
Yang, Bo,Wang, Zhong-Xia
, p. 4772 - 4784 (2020/05/01)
By choosing different phosphine ligands, nickel-catalyzed selective alkylation and reduction of allylic alcohols with alkyl Grignard reagents were performed. The reaction using Ni(dppe)Cl2 as the catalyst resulted in the cross-coupling of allylic alcohols with primary alkyl Grignard reagents and cyclopropylmagnesium bromide. The reaction catalyzed by the combination of Ni(PCy3)2Cl2 and dcype led to the reduction of allylic alcohols. Secondary alkyl Grignard reagents except cyclopropylmagnesium bromide always led to reduction of allylic alcohols using either Ni(dppe)Cl2 or Ni(PCy3)2Cl2/dcype as the catalyst. In the reductive reaction β-H-containing alkyl Grignard reagents were required.
Water as a Hydrogenating Agent: Stereodivergent Pd-Catalyzed Semihydrogenation of Alkynes
Zhao, Chuan-Qi,Chen, Yue-Gang,Qiu, Hui,Wei, Lei,Fang, Ping,Mei, Tian-Sheng
supporting information, p. 1412 - 1416 (2019/03/07)
Palladium-catalyzed transfer semihydrogenation of alkynes using H2O as the hydrogen source and Mn as the reducing reagent is developed, affording cis- and trans-alkenes selectively under mild conditions. In addition, this method provides an efficient way to access various cis-1,2-dideuterioalkenes and trans-1,2-dideuterioalkenes by using D2O instead of H2O.
Palladium-catalyzed double-bond migration of unsaturated hydrocarbons accelerated by tantalum chloride
Murai, Masahito,Nishimura, Kengo,Takai, Kazuhiko
supporting information, p. 2769 - 2772 (2019/03/23)
The operationally simple palladium-catalyzed double-bond migration without heteroatom-containing coordinating functional groups is described. Addition of TaCl5 as a second catalyst greatly enhanced the migration efficiency to provide β-alkylsty
Stereodivergent synthesis of alkenes by controllable syn-/anti-fragmentation of β-hydroxysulfonyl intermediates
Górski, Bartosz,Basiak, Dariusz,Grzesiński, ?ukasz,Barbasiewicz, Micha?
, p. 7660 - 7663 (2019/08/30)
The reduction of the carbonyl group in acylated trifluoroethyl alkanesulfonates follows the Felkin-Ahn selectivity, and the so-formed diastereomeric β-hydroxysulfonyl intermediates undergo syn- and anti-fragmentation, depending on the reaction conditions. In effect, isomeric E- and Z-alkenes are formed in a stereodivergent manner, which mimics the mechanistic manifold of the Peterson olefination.
Acceptorless dehydrogenative construction of CN and CC bonds through catalytic aza-Wittig and Wittig reactions in the presence of an air-stable ruthenium pincer complex
Biswas, Nandita,Das, Kalicharan,Sardar, Bitan,Srimani, DIpankar
, p. 6501 - 6512 (2019/05/24)
The construction of CN bonds was achieved by the dehydrogenative coupling of alcohol and azide via aza-Wittig type reaction. The reaction is catalyzed by an acridine-derived ruthenium pincer complex and does not use any oxidant. The present protocol offers a wide substrate scope, including aliphatic, aryl or heteroaryl alcohol/azides. This expeditious protocol was successfully applied to construct a CC bond directly from alcohol via dehydrogenative Wittig reaction. Furthermore, the synthesis of structurally important pyrrolo[1,4]benzodiazepine derivatives was also achieved by this methodology.
P-Chiral Monophosphorus Ligands for Asymmetric Copper-Catalyzed Allylic Alkylation
Xiong, Wenrui,Xu, Guangqing,Yu, Xinhong,Tang, Wenjun
, p. 4003 - 4013 (2019/06/24)
Asymmetric copper-catalyzed allylic alkylation between allyl bromides and alkyl Grignard reagents using a P-chiral monophosphorus ligand is described. A range of terminal olefins bearing tertiary or quaternary carbon centers were formed in good branched/linear selectivities and excellent enantioselectivities at copper loadings as low as 0.5 mol %.
Iron-Catalyzed Dihydrosilylation of Alkynes: Efficient Access to Geminal Bis(silanes)
Hu, Meng-Yang,Lian, Jie,Sun, Wei,Qiao, Tian-Zhang,Zhu, Shou-Fei
, p. 4579 - 4583 (2019/03/19)
Geminal bis(silanes) are versatile synthetic building blocks owing to their stability and propensity to undergo a variety of transformations. However, the scarcity of catalytic methods for their synthesis limits their structural diversity and thus their utility for further applications. Herein we report a new method for synthesis of geminal bis(silanes) by means of iron-catalyzed dihydrosilylation of alkynes. Iron catalysts were distinctly superior to the other tested catalysts, which clearly demonstrates that novel reactivity can be found by using iron catalysts. This method features 100% atom economy, regiospecificity, mild reaction conditions, and readily available starting materials. Using this method, we prepared a new type of geminal bis(silane) with secondary silane moieties, the Si-H bonds of which can easily undergo various transformations, facilitating the synthetic applications of these compounds. Preliminary mechanistic studies demonstrated that the reaction proceeds via two iron-catalyzed hydrosilylation reactions, the first generating β-(E)-vinylsilanes and the second producing geminal bis(silanes).
