Lewis or Brønsted acid-catalysed reaction of propargylic alcohol-tethered alkylidenecyclopropanes with indoles and pyrroles for the preparation of polycyclic compounds tethered with indole or pyrrole motif

Abstract

We developed a facile synthetic method to access the cyclopenta[b]naphthalene skeleton from Lewis or Brønsted acid-catalysed propargylic alcohol-tethered alkylidenecyclopropanes with indole and pyrrole derivatives.

Small rings in the bigger picture: ring expansion of three- and four-membered rings to access larger all-carbon cyclic systems

“…The resulting The interesting biological activity profile and structural complexity of cyclopenta [b]naphthalene moieties have drawn significant attention 119 and Shi proposed a straightforward access to this kind of structural motifs starting from the famously strained and reactive methylenecyclopropenes. 120 Under acidic conditions and in presence of a nucleophile (like indole or pyrrole) in the reaction mixture, the propargyl alcohol 163 underwent a cascade reaction to the polyaromatic structure 164 (Scheme 50). First, the carbocationic intermediates 165 could react with pyrrole (or indole) at the 2-or 1-position leading to intermediate 166 or side product 167.…”

Tandem Annulations of Propargylic Alcohols to Indole Derivatives

“…Examples described above mainly concentrated on the intramolecular annulations between indole moiety and propargylic alcohols. In fact, since the seminal work of Yadav in reporting a Sc(OTf) 3 -catalysed C3-alkylation of indole with propargylic alcohols, [51] the intermolecular reactions between indole and propargylic alcohols have also been investigated thoroughly to construct C3-propargylated indoles, C3-allenylated indoles and C3-arylated indoles via direct propargylic substitution, [52] and especially to construct indolecontaining hetero-and carbocycles via sequential propargylic substitution and cycloiso-merization under Brønsted or Lewis acid catalysis.…”

Visible-light-induced reactions of methylenecyclopropanes (MCPs)

“…These reactions can access cyclopropane-containing frameworks and other ring-opened compounds that are challenging to obtain conventionally. 4 These transformations usually occur smoothly under mild reaction conditions such as with heating, 5 Lewis/Brønsted acids, 6 transition metal catalysis, 7 radical-promoted processes, 8 and nucleophilic species-promoted ring-opening reactions, 9 giving tremendous potential in organic synthesis (Scheme 2).…”