Unusual Highly Diastereoselective Rh(II)-catalyzed Dimerization of Diazo Arylidene Succinimides Provides Access to New Dibenzazulene Scaffold

Abstract

Formation of unusual unsymmetrical dimers or/and indenes via Rh2(esp)2-catalyzed decomposition of diazo arylidene succinimides has been investigated. The reaction proceeded under mild conditions, and its result was shown to strongly depend on the nature of the substituents in the diazo substrate. The new reaction provides access to dibenzoazulenodipyrrole and indenopyrrole derivatives in moderate to high yield. Dibenzoazulenodipyrroles bearing alkyl substituents at the nitrogen atom showed pronounced cytotoxocity against A549 human lung adenocarcinoma cell line while N-aryl analogs were non-cytotoxic.

Novel spirocyclic scaffold accessed via tandem Claisen rearrangement – intramolecular Michael addition

“…The O-H insertion reaction worked well for electron-neutral or electron-rich phenols. The presence of electron-withdrawing substituents (such as 4-Cl or 2,4-diCl) in the phenol component drastically diminished the yield and led to the formation of the earlier reported DAS dimer [11]. Similarly, electron-donating groups (such as 4-methnoxy) in the arylidene portion of 1 complicated the course of the reaction.…”