767-91-9Relevant academic research and scientific papers
Iodocyclisation of Electronically Resistant Alkynes: Synthesis of 2-Carboxy (and sulfoxy)-3-iodobenzo[ b ]thiophenes
Chen, Shuqi,Flynn, Bernard L.
, p. 65 - 76 (2020/11/05)
The iodocyclisation of alkynes bearing tethered nucleophiles is a highly effective method for the construction and diversification of heterocycles. A key limitation to this methodology is the 5-endo-dig iodocyclisation of alkynes that have an unfavourable electronic bias for electrophilic cyclisation. These tend to direct electrophilic attack of the iodonium atom to the wrong carbon for cyclisation, thus favouring competing addition reactions. Using our previously determined reaction conditions for the 5-endo-dig iodocyclisations of electronically resistant alkynes, we have achieved efficient synthetic access to 2-carboxy (and sulfoxy)-3-iodobenzo[b]thiophenes. The corresponding benzo[b]furans and indoles were not accessible under these conditions. This difference may arise due to the availability of a radical mechanism in the case of iodobenzo[b]thiophenes. The 2-carboxy functionality of the iodocyclised products can be further employed in iterative alkyne-coupling iodocyclisation reactions, where the carboxy group or an imine (Schiff base) partakes in a second iodocyclisation to generate a lactone or pyridine ring.
Biomimetic carbene cascades enabled imine derivative migration from carbene -bearing thiocarbamates
Li, Xue,Chen, Haohua,Xuan, Qingqing,Mai, Shaoyu,Lan, Yu,Song, Qiuling
supporting information, p. 3518 - 3523 (2021/05/29)
Inspired by the body circulation of Omeprazole (irreversible proton pump inhibitor), we disclose the carbene-triggered cascades for the synthesis of 2-aminobenzofuran derivatives from N-sulfonyl-1,2,3-triazoles or benzothioazole-bearing thiocarbamates, which represents an unprecedented imine derivative migration process. Furthermore, the desulfurizing reagent-free Barton-Kellogg-type reactions starting from N-sulfonyl-1,2,3-triazoles have also been achieved for the first time, and elemental sulfur is confirmed as a byproduct during this transformation. Both experimental data and DFT calculations further thoroughly explained the unique reactivity.
Divergent Carbocatalytic Routes in Oxidative Coupling of Benzofused Heteroaryl Dimers: A Mechanistic Update
Casadio, David S.,Aikonen, Santeri,Lenarda, Anna,Nieger, Martin,Hu, Tao,Taubert, Stefan,Sundholm, Dage,Muuronen, Mikko,Wirtanen, Tom,Helaja, Juho
supporting information, p. 5283 - 5291 (2021/02/26)
Mildly thermal air or HNO3 oxidized activated carbons catalyse oxidative dehydrogenative couplings of benzo[b]fused heteroaryl 2,2’-dimers, e.g., 2-(benzofuran-2-yl)-1H-indole, to chiral 3,3’-coupled cyclooctatetraenes or carbazole-type migrative products under O2 atmosphere. DFT calculations show that the radical cation and the Scholl-type arenium cation mechanisms lead to different products with 2-(benzofuran-2-yl)-1H-indole, being in accord with experimental product distributions.
B(C6F5)3-Catalyzed cyclization of alkynes: direct synthesis of 3-silyl heterocyclic compounds
Li, Mengxing,Wang, Ting,An, Zhenyu,Yan, Rulong
supporting information, p. 11953 - 11956 (2020/10/15)
An efficient one-pot strategy for easy access to 3-silyl heterocyclic compounds was developedviaa B(C6F5)3-catalyzed cycloaddition reaction ofo-(1-alkynyl)(thio)anisoles oro-(1-alkynyl)-N-methylaniline. In this reaction, benzenethiophene, benzofuran or indole skeletons could be constructed by an intermolecular cyclization with diphenylsilane. This protocol elicited moderate-to-good yields with metal-free reaction systems.
Design, synthesis and application of triazole ligands in suzuki miyaura cross coupling reaction of aryl chlorides
Jabeen, Sobia,Khera, Rasheed Ahmad,Iqbal, Javed,Asgher, Muhammad
, (2020/01/28)
DFT calculations have been demonstrated to be a valuable tool for the mechanistic study of reaction which is difficult to acquire from pure experimental techniques. Structural, electronic and coordination aspects of synthesized triazole ligands were investigated theoretically by structure optimization on Gaussian 09 package by DFT approach at B3LYP/6-31G (d, p). HOMO-LUMO energy gaps correlated to its chemical reactivity and this information applied to interpret the role of ligand in the formation of ligand-metal complex. Electron rich environment around the triazole core stabilized the HOMO orbital and made these electrons available to form complex with Pd centre. The DFT calculations provide a plausible mechanism for the reaction that is consistent with the available experimental facts. A series of triazole ligands have been synthesized via efficient 1,3-dipolar cycloaddition of readily available azide and alkynes for coordination to Pd centre. Characterization of all the synthesized compounds was done by FTIR, 1H NMR, 13C NMR and HRMS. Their ligand-Pd complexes provided excellent yields in the Suzuki-Miyaura coupling reactions (up to 92% yield) of unactivated aryl chlorides. Ligand 4-(2,6-dimethoxyphenyl)-1-phenyl-1H-1,2,3-triazole (L2) was found to be most effective ligand because of electron donating 2,6 dimethoxy phenyl moiety attached to triazole ring at 4-position that facilitated the formation of electron rich ligand-catalyst complex. The complex favoured the oxidative addition step of Pd across the aryl chloride substrate and thus allowed for the development of highly active ligand-catalyst system for Suzuki reaction. During computational analysis, 4-(2,6-dimethoxyphenyl)-1-phenyl-1H-1,2,3-triazole (L2) also showed lowest band gap due to electron rich distribution pattern on the HOMO that are involve in ligand-Pd complex formation. Conclusively, these triazoles ligands were found to be more competent and attractive for palladium catalyst because of simplistic pathway for the synthesis of triazole motif and the ease of individual tuning of the substituents on triazole core or exocyclic to it.
CO-Free Enantioselective Hydroformylation of Functionalised Alkenes: Using a Dual Catalyst System to Give Improved Selectivity and Yield
Pittaway, Rachael,Dingwall, Paul,Fuentes, José. A.,Clarke, Matthew. L.
supporting information, p. 4334 - 4341 (2019/08/21)
The scope of carbon monoxide-free Asymmetric Transfer HydroFormylation (ATHF) procedures using a highly active single catalyst system derived from 1,2-bis-((2,5)-diphenylphospholano)ethane as chiral ligand has been studied. This reveals some highly successful reactions, but also significant limitations. The development of a new protocol in which a catalyst for formaldehyde decomposition to CO and H2 is combined with the catalyst of choice for the subsequent asymmetric hydroformylation is described. This enables ATHF reactions that were problematic to be significantly improved. The new method has been used in the synthesis of several key precursors to biologically active molecules. (Figure presented.).
Regioselective Gold-Catalyzed Hydration of CF3- and SF5-alkynes
Cloutier, Mélissa,Roudias, Majdouline,Paquin, Jean-Fran?ois
supporting information, p. 3866 - 3870 (2019/05/24)
The regioselective gold-catalyzed hydration of CF3- and SF5-alkynes is described. The corresponding trifluoromethylated and pentasulfanylated ketones are obtained in up to 91% yield as single regioisomers showcasing the use of CF3 and SF5 as highly efficient directing groups in this reaction. Notably, this transformation represents the first use of CF3- and SF5-alkynes in gold catalysis.
Synthesis of Triazole Click Ligands for Suzuki-Miyaura Cross-Coupling of Aryl Chlorides
Jabeen,Khera,Iqbal,Asgher
, p. 1416 - 1422 (2019/11/03)
A series of new triazole ligands has been synthesized via copper-catalyzed cycloaddition reaction of readily available azides and alkynes. The synthesized compounds were characterized by FTIR, 1H and 13C NMR, and high-resolution mass spectra. The ligands provided excellent yields (up to 92%) in the palladium-catalyzed Suzuki-Miyaura cross coupling of unactivated aryl chlorides with phenylboronic acid. 1-Benzyl-4-(2,6-dimethoxyphenyl)-lH-1,2,3-triazole was found to be the most effective ligand due to the presence of electron-donating 2,6-dimethoxyphenyl substituent, which made it possible to develop a highly active ligand-catalyst system for the Suzuki reaction of aryl chlorides.
DBU-Mediated Synthesis of Aryl Acetylenes or 1-Bromoethynylarenes from Aldehydes
Thummala, Yadagiri,Karunakar, Galla V.,Doddi, Venkata Ramana
supporting information, p. 611 - 616 (2019/01/04)
Two well known synthetic organic reactions Ramirez olefination and Corey-fuchs reactions are integrated in one-pot sequential manner for the synthesis of arylacetylenes and 1,3-enynes starting directly from commercially available aldehydes. The bicyclic amidine 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) along with additive NaOH not only exclusively afforded the terminal alkynes directly from the aldehydes, but also enhanced the reaction rate. The dynamic nature of DBU also facilitated the isolation of 1-bromoalkynes intermediate products. Selection of additive from NaOH and H2O served as a switch for the synthesis of terminal alkyne and 1-bromoalkynes, respectively. (Figure presented.).
A Traceless Tether Strategy for Achieving Formal Intermolecular Hexadehydro-Diels-Alder Reactions
Smela, Merrick Pierson,Hoye, Thomas R.
supporting information, p. 5502 - 5505 (2018/09/12)
A synthetic strategy formally equivalent to an intermolecular hexadehydro-Diels-Alder (HDDA) reaction is described. Sulfur-based linkers were designed and constructed by joining terminal alkynes or diynes using alkyne thiolate chemistry. The resulting tetraynes and triynes successfully underwent HDDA cyclization and benzyne trapping. Linker removal by reductive desulfurization was uneventful. The strategy was also found suitable for the tetradehydro-Diels-Alder (TDDA) reaction.
