4250-82-2Relevant academic research and scientific papers
Inhibition of Reductive Elimination of Diorganopalladium Species by Formation of Tetraorganopalladates
Negishi, Ei-ichi,Akiyoshi, Kazunari,Takahashi, Tamotsu
, p. 477 - 478 (1987)
Reductive elimination of (tBuCC)2Pd(PPh3)2 to give tBuCCCCBut (4) is strongly inhibited by an excess of LiCCBut through the formation of Li2Pd(CCBut)4, which does not readily decompose to produce (4); these results provide, for the first time, a mechanistic interpretation of the hitherto puzzling inhibitory action of highly electropositive metals, such as Li, in Pd-promoted coupling reactions.
Nickel-Catalyzed Sonogashira Coupling Reactions of Nonactivated Alkyl Chlorides under Mild Conditions
Fan, Qingqing,Sun, Hongjian,Xie, Shangqing,Dong, Yanhong,Li, Xiaoyan,Fuhr, Olaf,Fenske, Dieter
, p. 2240 - 2245 (2021/04/06)
The two nickel chlorides1and2with [P,S] and [P,Se] bidentate ligands, respectively, were synthesized and used as catalysts for Sonogashira coupling reaction. Both1and2are efficient catalysts for Sonogashira C(sp3)-C(sp) coupling reactions. Comp
An Amine-Assisted Ionic Monohydride Mechanism Enables Selective Alkyne cis-Semihydrogenation with Ethanol: From Elementary Steps to Catalysis
Huang, Zhidao,Wang, Yulei,Leng, Xuebing,Huang, Zheng
supporting information, p. 4824 - 4836 (2021/04/07)
The selective synthesis of Z-alkenes in alkyne semihydrogenation relies on the reactivity difference of the catalysts toward the starting materials and the products. Here we report Z-selective semihydrogenation of alkynes with ethanol via a coordination-induced ionic monohydride mechanism. The EtOH-coordination-driven Cl- dissociation in a pincer Ir(III) hydridochloride complex (NCP)IrHCl (1) forms a cationic monohydride, [(NCP)IrH(EtOH)]+Cl-, that reacts selectively with alkynes over the corresponding Z-alkenes, thereby overcoming competing thermodynamically dominant alkene Z-E isomerization and overreduction. The challenge for establishing a catalytic cycle, however, lies in the alcoholysis step; the reaction of the alkyne insertion product (NCP)IrCl(vinyl) with EtOH does occur, but very slowly. Surprisingly, the alcoholysis does not proceed via direct protonolysis of the Ir-C(vinyl) bond. Instead, mechanistic data are consistent with an anion-involved alcoholysis pathway involving ionization of (NCP)IrCl(vinyl) via EtOH-for-Cl substitution and reversible protonation of Cl- ion with an Ir(III)-bound EtOH, followed by β-H elimination of the ethoxy ligand and C(vinyl)-H reductive elimination. The use of an amine is key to the monohydride mechanism by promoting the alcoholysis. The 1-amine-EtOH catalytic system exhibits an unprecedented level of substrate scope, generality, and compatibility, as demonstrated by Z-selective reduction of all alkyne classes, including challenging enynes and complex polyfunctionalized molecules. Comparison with a cationic monohydride complex bearing a noncoordinating BArF- ion elucidates the beneficial role of the Cl- ion in controlling the stereoselectivity, and comparison between 1-amine-EtOH and 1-NaOtBu-EtOH underscores the fact that this base variable, albeit in catalytic amounts, leads to different mechanisms and consequently different stereoselectivity.
Direct Photoexcitation of Ethynylbenziodoxolones: An Alternative to Photocatalysis for Alkynylation Reactions**
Amos, Stephanie G. E.,Cavalli, Diana,Le Vaillant, Franck,Waser, Jerome
supporting information, p. 23827 - 23834 (2021/09/25)
Ethynylbenziodoxolones (EBXs) are commonly used as radical traps in photocatalytic alkynylations. Herein, we report that aryl-substituted EBX reagents can be directly activated by visible light irradiation. They act as both oxidants and radical traps, alleviating the need for a photocatalyst in several reported EBX-mediated processes, including decarboxylative and deboronative alkynylations, the oxyalkynylation of enamides and the C?H alkynylation of THF. Furthermore, the method could be applied to the synthesis of alkynylated quaternary centers from tertiary alcohols via stable oxalate salts and from tertiary amines via aryl imines. A photocatalytic process using 4CzIPN as an organic dye was also developed for the deoxyalkynylation of oxalates.
Phosphorus(III)-Mediated, Tandem Deoxygenative Geminal Chlorofluorination of 1,2-Diketones
Choi, Garam,Chung, Won-Jin,Hwang, Sunjoo,Jang, Hanna,Kim, Ha Eun
supporting information, p. 4190 - 4195 (2020/06/27)
Tetrasubstituted carbon containing two different halogen substituents was constructed in a single-step operation by utilizing the carbene-like reactivity of dioxaphospholene through the tandem reaction of electrophilic and nucleophilic halogenating reagents. It was crucial to devise non-dealkylatable phosphoramidite, which enabled the efficient formation of geminal chlorofluorides from various 1,2-diketones with (PhSO2)2NF and n-Bu4NCl. In addition, selective functionalization of the chlorine substituent was demonstrated, and the absence of halogen scrambling was confirmed.
Nickel-Catalyzed Allylmethylation of Alkynes with Allylic Alcohols and AlMe3: Facile Access to Skipped Dienes and Trienes
Li, Jincan,Li, Wanfang,Yu, Shun,Zhao, Yu
supporting information, p. 14404 - 14408 (2020/07/04)
We present herein an unprecedented allylative dicarbofunctionalization of alkynes with allylic alcohols. This simple catalytic procedure utilizes commercially available Ni(COD)2, triphenylphosphine, and inexpensive reagents, and delivers valuable skipped dienes and trienes with an all-carbon tetrasubstituted alkene unit in a highly stereoselective fashion. Preliminary mechanistic studies support the reaction pathway of allylnickelation followed by transmetalation in this dicarbofunctionalization of alkynes.
Practical synthesis of α,β-Alkynyl ketones by oxidative alkynylation of aldehydes with hypervalent alkynyliodine reagents
Tsuzuki, Saori,Sakamoto, Ryu,Maruoka, Keiji
supporting information, p. 633 - 636 (2020/10/08)
A practical, metal-free carbonyl C(sp2)H oxidative alkynylation of aldehydes with hypervalent alkynyliodine reagents without the use of any catalysts is described for the synthesis of various α,β-alkynyl ketones. Here, two different methods have been developed where limiting reagents or substrates can be switched, and adopted according to the valuableness of aldehyde substrates or hypervalent alkynyliodine reagents. These reactions proceed with a broad substrate scope and high functional-group compatibility.
Diborative Reduction of Alkynes to 1,2-Diboryl-1,2-Dimetalloalkanes: Its Application for the Synthesis of Diverse 1,2-Bis(boronate)s
Takahashi, Fumiya,Nogi, Keisuke,Sasamori, Takahiro,Yorimitsu, Hideki
supporting information, p. 4739 - 4744 (2019/06/27)
Reduction of alkynes with alkali metals in the presence of B2pin2 results in diboration of alkynes. Distinct from conventional dissolving metal hydrogenations, two carbon-boron bonds and also two carbon-alkali metal bonds can be constructed in one operation to form 1,2-diboryl-1,2-dimetalloalkanes. The 1,2-diboryl-1,2-dimetalloalkanes generated are readily convertible to a wide range of vicinal bis(boronate)s. In particular, oxidation of the 1,2-dianionic species provides (E)-1,2-diborylalkenes, unique anti-selective diboration of alkynes being thus executed.
Electrochemical synthesis of 1,2-diketones from alkynes under transition-metal-catalyst-free conditions
Zhou, Jie,Tao, Xiang-Zhang,Dai, Jian-Jun,Li, Chen-Guang,Xu, Jun,Xu, Hong-Mei,Xu, Hua-Jian
supporting information, p. 9208 - 9211 (2019/08/07)
We report an electrochemical protocol for the direct oxidation of internal alkynes in air to provide 1,2-diketones. A variety of functional groups and heterocycle-containing substrates can be tolerated well under mild conditions.
1-Aryltriazenes in the Suzuki, Heck, and Sonogashira Reactions in Imidazolium-ILs, with [BMIM(SO3H)][OTf] or Sc(OTf)3 as Promoter, and Pd(OAc)2 or NiCl2·glyme as Catalyst
Sutar, Suraj M.,Savanur, Hemantkumar M.,Malunavar, Shruti S.,Prabhala, Pavankumar,Kalkhambkar, Rajesh G.,Laali, Kenneth K.
, p. 6088 - 6093 (2019/09/17)
1-Aryltriazenes, the protected and more stable form of aryl-diazonium species, can be conveniently unmasked with Br?nsted acidic-IL or Sc(OTf)3 and coupled with a host of aryl/heteroaryl boronic acids, styrenes, and aryl/alkyl acetylenes in the Suzuki, Heck and Sonogashira reactions in one-pot and in respectable isolated yields, by using palladium or nickel catalyst in readily available imidazolium ILs as solvent, under mild conditions. The scope of these reactions are explored, and the potential for recovery/reuse of the IL solvent is also addressed.
