- Alcohol Etherification via Alkoxy Radicals Generated by Visible-Light Photoredox Catalysis
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A mechanistically divergent method is described that, employing a commercially available hypervalent iodine(III) reagent, generates alkoxy radicals from 1°, 2°, and 3° alcohols and allows their use in the functionalization of C(sp3)-H and C(sp2)-H bonds. This visible-light photoredox catalysis produces alkyl ethers via 1,5/6-hydrogen atom transfer or aryl ethers via 1,5-addition. This mild methodology provides a practical strategy for the synthesis of acetals, orthoesters, tetrahydrofurans, and chromanes.
- Rivero, Alexandra R.,Fodran, Peter,Ondrejková, Alica,Wallentin, Carl-Johan
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p. 8436 - 8440
(2020/11/03)
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- Conformational analysis of 3-substituted-2,3,4,5-tetrahydro-1-benzoxepin by 1H and 13C nuclear magnetic resonance
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2,3,4,5-Tetrahydro-1-benzoxepin (8) and its 3-substituted derivatives (9-13) have been studied by 1H and 13C dynamic nuclear magnetic resonance in a few solvent systems.The results show that, while 8 and its methyl derivative 9 exist solely in chair forms (C for 8 and Ce:Ca (96:4) for 9), the twist-boat (TB) conformation contributes significantly to the conformational equilibra of the derivatives 3-methoxy 10 (Ca:Ce:TB, 70:20:10), 3,3-dimethyl 11 (C:TB, 90:10), 3,3-methylmethoxy 12 (Ca:Ce:TB, 89:4:7), and 3,3-dimethoxy 13 (C:TB, 92:8).The analysis of several factors (steric, electrostatic, and electronic) on the conformational behaviour of these molecules shows why the TB form is a viable conformational alternative to destabilized chair forms in this benzoxepin system.
- Lachapelle, A.,St-Jacques, M.
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p. 2575 - 2594
(2007/10/02)
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- Rate Constants for the Cyclisation of Some Aryl Radicals bearing Unsaturated ortho-Substituents
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Rate constants and Arrhenius parameters have been determined for ring-closure of o-alkenyl- and o-alkenyloxy-aryl radicals, and for deuterium atom transfer from tributyltin deuteride.
- Abeywickrema, Anil N.,Beckwith, Athelstan L. J.
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p. 464 - 465
(2007/10/02)
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- Oxidation of Arylalkanols by S2O82--CuII
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Products of oxidation of a series of arylalkanols by S2O82--CuII in acetic acid and acetonitrile are consistent with initial oxidation to aryl radical cations followed by either loss of a benzylic proton or C-C bond scission and subsequent oxidation of intermediate benzylic radicals by CuII to final products. 1-Arylalkanols (ArCHOHR)react by both paths, C-C bond scission increasing with stability of the radical R.. 2-Arylalkanols (ArCH2CHOHR) give chiefly C-C bond scission to benzyl radicals and RCHO.The 3- and 4-arylalkanols undergo chiefly proton loss, and the resulting radicals are oxidized with cyclization to chromans and 2-phenylfurans, respectively, both of which may by oxidized in turn to further products.
- Walling, Cheves,El-Taliawi, Gamil M.,Zhao, Chengxue
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p. 4914 - 4917
(2007/10/02)
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