Scheme 5. (a) Hydrothiolation of ynone 20; (b) Hydrothiolation of alkyne 22; (c) UV-Vis spectroscopy studies of indole-tethered ynone 13g compared with model reaction components; (d) UV-Vis spectroscopy of indole-tethered ynones (13g, 13k, 13l, 13p) and propargylic alcohol 13q. All UV-Vis experiments were performed in anhydrous 1,2-dichloroethane (0.02 M).