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Volumn 54, Issue 5, 2015, Pages 1485-1489

X-ray characterization of an electron donor-acceptor complex that drives the photochemical alkylation of indoles

Author keywords

Alkylation; Indoles; Photochemistry; Radicals; Synthetic methods

Indexed keywords

ALKYLATION; ASSOCIATION REACTIONS; CHARGE TRANSFER; PHOTOCHEMICAL REACTIONS; SINGLE CRYSTALS;

EID: 85027924410     PISSN: 14337851     EISSN: 15213773     Source Type: Journal    
DOI: 10.1002/anie.201409529     Document Type: Article
Times cited : (185)

References (54)
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    • Molecular oxygen can quench the excited EDA triplet state, thereby interrupting the ET process leading to the radical ion pair III (Figure 1b). The radical mechanism was further corroborated by the experiments conducted in the presence of 2, 6-di-tert-butyl-4-methylphenol (0.5 equiv), since product 3a was not detected after prolonged exposure to light
    • Molecular oxygen can quench the excited EDA triplet state, thereby interrupting the ET process leading to the radical ion pair III (Figure 1b). The radical mechanism was further corroborated by the experiments conducted in the presence of 2, 6-di-tert-butyl-4-methylphenol (0.5 equiv), since product 3a was not detected after prolonged exposure to light.
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    • CCDC 1025725 (IIa) and 1025726 (6) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data-request/cif.
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    • While crystals of II a could be safely stored for four months in the dark at 0°C, irradiation from a 23 W CFL induced a fast yet unproductive degradation, as the alkylation product 3a was not detected. The lack of reactivity in the crystalline state could be a consequence of either the absence of base (the model reaction in MeOH does not proceed at all without 2, 6-lutidine) or an unproductive orientation of the substrates 1a and 2a in the solid state, as dictated by stabilizing packing interactions according to Mulliken's "Overlap and Orientation Principle", see Wiley, New York
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    • Although our studies do not definitively rule out a radical chain mechanism, they suggest that any chain propagation process must be short-lived to account for a quantum yield as low as 0.2.
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