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- Title
Visible light mediated photocatalytic [2 + 2] cycloaddition/ring-opening rearomatization cascade of electron-deficient azaarenes and vinylarenes.
- Authors
Salaverri, Noelia; Mas-Ballesté, Rubén; Marzo, Leyre; Alemán, José
- Abstract
The broad presence of azaarene moieties in natural products has promoted the development of new functionalization reactions, giving access to larger libraries of bioactive compounds. The light promoted [2 + 2] photocycloaddition reaction to generate cyclobutanes has been extensively studied in photochemistry. In particular, De Mayo reported the [2 + 2] cycloaddition followed by retroaldol condensation between enols of 1,3-dicarbonyls and double bonds to synthesize 1,5-dicarbonyls. Herein, we describe the [2 + 2] photocycloaddition followed by a ring-opening rearomatization reaction between electron-deficient 2-methylene-azaarenes and double bonds, taking advantage of the ability of these heterocyclic derivatives to form the corresponding pseudo-enamine intermediate. The procedure shows a high functional group tolerance either on the double bond or the heteroarene side and allows the presence of different electron-withdrawing groups. In addition, the wide applicability of this reaction has been demonstrated through the late-stage derivatization of several natural products. Photochemical studies, together with theoretical calculations, support a mechanism involving the photosensitization of the pseudo-enamine intermediate. The visible light-promoted [2 + 2] cycloaddition is a useful and extended route to prepare cyclobutanes and their derivatives. Here, we present an aza variant, in which heterocycles and olefins undergo a cycloaddition-ring opening rearomatization sequence, providing access to functionalised nitrogen heterocycles.
- Subjects
AROMATIZATION; ELECTRON-deficient compounds; RING formation (Chemistry); BIOACTIVE compounds; DOUBLE bonds
- Publication
Communications Chemistry, 2020, Vol 3, Issue 1, pN.PAG
- ISSN
2399-3669
- Publication type
Article
- DOI
10.1038/s42004-020-00378-x