Gadolinium Photocatalysis: Dearomative [2+2] Cycloaddition/Ring-Expansion Sequence with Indoles |
| |
Authors: | Dr Jiajia Ma Felix Schäfers Dr Constantin Daniliuc Dr Klaus Bergander Prof Dr Cristian A Strassert Prof Dr Frank Glorius |
| |
Institution: | 1. Organisch-Chemisches Institut, Westfälische Wilhelms-Universität Münster, Corrensstrasse 40, 48149 Münster, Germany;2. CeNTech, CiMIC, SoN, Institut für Anorganische und Analytische Chemie, Westfälische Wilhelms-Universität Münster, Heisenbergstraße 11, 48149 Münster, Germany |
| |
Abstract: | Lanthanide photocatalysts are much less investigated in synthetic chemistry than rare and expensive late transition metals. We herein introduce GdIII photocatalysis of a highly regioselective, intermolecular 2+2] photocycloaddition/ring-expansion sequence with indoles, which could provide divergent access to cyclopentab]indoles and indolines. A simple and commercially available Gd(OTf)3 salt is sufficient for this visible-violet-light-induced transformation. The reaction proceeds either through a transient or start-to-end dearomatization cascade and shows excellent regioselectivity (usually >95:5 r.r.), broad scope (59 examples), good functional group tolerance and facile scale-up under mild, direct visible-light-excitation conditions. Mechanistic investigations reveal that direct excitation of the Gd(OTf)3/indole mixture gives an excited state intermediate, which undergoes the subsequent 2+2] cycloaddition and cyclobutane-expansion cascade. |
| |
Keywords: | [2+2]-Photocycloaddition Dearomatisierung Gadolinium Ringerwieterung Photokatlyse mit sichtbarem Licht |
|
|