- Catalytic Hydroetherification of Unactivated Alkenes Enabled by Proton-Coupled Electron Transfer
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We report a catalytic, light-driven method for the intramolecular hydroetherification of unactivated alkenols to furnish cyclic ether products. These reactions occur under visible-light irradiation in the presence of an IrIII-based photoredox catalyst, a Br?nsted base catalyst, and a hydrogen-atom transfer (HAT) co-catalyst. Reactive alkoxy radicals are proposed as key intermediates, generated by direct homolytic activation of alcohol O?H bonds through a proton-coupled electron-transfer mechanism. This method exhibits a broad substrate scope and high functional-group tolerance, and it accommodates a diverse range of alkene substitution patterns. Results demonstrating the extension of this catalytic system to carboetherification reactions are also presented.
- Knowles, Robert R.,Metrano, Anthony J.,Tsuchiya, Yuto,Tsui, Elaine
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supporting information
p. 11845 - 11849
(2020/05/22)
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- Stereoselective Synthesis of cis-2,5-Disubstituted Pyrrolidines via Copper-Catalyzed Cyclization of Alkenes
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An efficient methodology for the stereoselective synthesis of cis-2,5-disubstituted pyrrolidines using copper catalyst was developed. The corresponding cis-2,5-disubstituted pyrrolidines could be obtained in reasonable yields and with good stereoselectivities in the presence of 4,4′-di-tert-butyl-2,2′-bipyridine as ligand and 1-methyl-2-pyrrolidinone as solvent.
- Cai, Sai-Hu,Da, Bing-Chao,Zhou, Jia-Hui,Xu, Yun-He,Loh, Teck-Peng
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supporting information
p. 1076 - 1080
(2016/11/25)
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- Sodium amalgam mediated desulfonylative reduction of α-functionalized β-ketosulfones
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Sodium amalgam mediated desulfonylative reduction of β-ketosulfones in MeOH at rt affords alcohols in good yields via radical desulfonylation of β-ketosulfones and sequential Bouveault-Blanc reduction of the resulting ketones.
- Chan, Chieh-Kai,Huang, Yi-Hsuan,Chang, Meng-Yang
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p. 5521 - 5529
(2016/08/04)
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- Prins cyclization of α-bromoethers under basic conditions
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α-Bromoethers have been found to undergo Prins-type cyclization under basic conditions and without the need to add a promoter. The products are those derived from a Markovnikov addition on the pendant alkene. However, the stereochemistry and even the structure of the products sometimes differ from those expected with the classical Lewis-acid-catalyzed Prins reaction of acetals.
- Arpin, Patrice,Hill, Bryan,Larouche-Gauthier, Robin,Spino, Claude
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p. 1193 - 1201
(2014/01/06)
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- Lithiated carbamates: Chiral carbenoids for iterative homologation of boranes and boronic esters
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(Chemical Equation Presented) Take your pick: Either enantiomer of either diastereomer of substrates bearing adjacent stereogenic centers is accessible through reaction of an (R)- or (S)-lithiated carbamate with an (R)- or (S)-boronic ester (see scheme; pin = pinacolate, OCb = substituted carbamate).
- Stymiest, Jake L.,Dutheuil, Guillaume,Mahmood, Adeem,Aggarwal, Varinder K.
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p. 7491 - 7494
(2008/09/17)
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- Microwave-assisted generation of alkoxyl radicals and their use in additions, β-fragmentations, and remote functionalizations
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Microwave irradiation (2.45 GHz, 300-500 W) of N-(alkoxy)thiazole-2(3H)- thiones in low-absorbing solvents affords alkoxyl radicals, which were identified by (i) spin adduct formation (EPR-spectroscopy) and (ii) fingerprint-type selectivities in intramolecular additions (stereoselective synthesis of disubstituted tetrahydrofurans), β-fragmentations (formation of carbonyl compounds), and C,H-activation of aliphatic subunits, by δ-selective hydrogen atom transfer. C-Radicals formed from oxygen-centered intermediates were trapped either by Bu3SnH, l-cysteine ethyl ester, the reduced form of glutathione (reductive trapping), or by bromine atom donor BrCCl3 (heteroatom functionalization) The results suggest that microwave activation is superior to UV/Vis-photolysis and conductive heating for alkoxyl radical generation from N-(alkoxy)thiazolethiones. It offers by far the shortest reaction times along with the option to reduce the amount of trapping reagent significantly. The Royal Society of Chemistry 2006.
- Hartung, Jens,Daniel, Kristina,Gottwald, Thomas,Gross, Andreas,Schneiders, Nina
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p. 2313 - 2322
(2008/02/08)
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- HETEROCYCLISATIONS INDUCED BY THALLIUM(III) ACETATE. EFFECT OF VARYING THE INTERNAL NUCLEOPHILE
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The stereochemistry of the 2,5-disubstituted tetrahydrofuran formed on treating 5-methyl-1-phenylhex-4-en-1-ol (6) with thallium(III) acetate in appropriate solvents has been established as trans by means of nuclear Overhauser experiments.Replacement of t
- Michael, Joseph P.,Nkwelo, Mluleki M.
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p. 2549 - 2560
(2007/10/02)
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