Synthesis 2015; 47(18): 2869-2884
DOI: 10.1055/s-0034-1380756
paper
© Georg Thieme Verlag Stuttgart · New York

Photocycloaddition and Rearrangement Reactions in a Putative Route to the Skeleton of Plicamine-Type Alkaloids

Karl-Heinz Rimböck
Department Chemie and Catalysis Research Center (CRC), Technische Universität München, Lichtenbergstr. 4, 85747 Garching, Germany   Email: thorsten.bach@ch.tum.de
,
Alexander Pöthig
Department Chemie and Catalysis Research Center (CRC), Technische Universität München, Lichtenbergstr. 4, 85747 Garching, Germany   Email: thorsten.bach@ch.tum.de
,
Thorsten Bach*
Department Chemie and Catalysis Research Center (CRC), Technische Universität München, Lichtenbergstr. 4, 85747 Garching, Germany   Email: thorsten.bach@ch.tum.de
› Author Affiliations
Further Information

Publication History

Received: 13 April 2015

Accepted: 16 April 2015

Publication Date:
26 June 2015 (online)


Abstract

Two isoquinolones were prepared, to which an allenyl side chain was linked at position C4 via a stereogenic silyloxy-substituted carbon atom. Intramolecular [2+2] photocycloaddition reactions of these substrates proceeded with high diastereoselectivity and delivered the respective cyclobutanes with an exocyclic methylene group (83% and 49% yield). With the 5,6-dioxoloisoquinolone precursor an unprecedented meta-photocycloaddition was observed as a significant side reaction, which occurred at positions C4 and C8a of the isoquinolone skeleton. The cyclobutane products were, after N-alkylation and transformation into the respective cyclobutanones (22–57%), subjected to various rearrangement reactions. In detail, a direct photochemical rearrangement, thermal and photochemical Beckmann rearrangements, and Baeyer–Villiger oxidation reactions were studied. In all cases, products were found, which resulted from cleavage of the amino-substituted cyclobutane bond, but not from the desired cleavage of the alternative alkyl-substituted cyclobutane bond.

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