Brønsted-acid-catalyzed one-pot tandem annulation/[5 + 2]-cycloaddition of o-propargyl alcohol benzaldehydes with alkynes: regioselective and stereoselective synthesis of dibenzo[a,f]azulen-12-ones

Abstract

The one-pot synthesis of dibenzo[a,f]azulen-12-ones has been established starting from o-propargyl alcohol benzaldehydes and alkynes. The key azulenone bicyclic skeletons were formed through intramolecular Meyer-Schuster rearrangement and intermolecular [5+2]-cycloaddition sequence....

Dual Proton/Silver-Catalyzed Serial (5 + 2)-Cycloaddition and Nazarov Cyclization of (E)-2-Arylidene-3-hydroxyindanones with Conjugated Eneynes: Synthesis of Indanone-Fused Benzo[cd]azulenes

“…As pointed out in the design plan, the intermolecular (5 + 2)-cycloaddition is the prerequisite for the Nazarov cyclization. Based on our previous work, 17 we learned that proton acid was an effective catalyst for the (5 + 2)cycloaddition. Inspired by these facts, we made attempts to use metal/proton synergistic catalysis.…”

“…15 Expanding 2carbon π components to enynones or aryl-ynones, Wender has achieved Rh-catalyzed sequential intermolecular (5 + 2)cycloaddition/Nazarov cyclization with VCPs for the facile synthesis of bicyclo [5.3.0] decanes (Scheme 1d). 16 Inspired by this ingenious strategy and based on our previous research on the application of in situ generated (E)-2-arylidene-3- hydroxyindanones as 5C synthons, 17 we envisaged combining (E)-2-arylidene-3-hydroxyindanones with conjugated eneynes in the presence of the dual catalysis of an acid and a transition metal could provide alkenyl-substituted azulenone intermediates, which might undergo a subsequent Nazarov cyclization (Scheme 1e). Herein, we report the first study of sequential (5 + 2)-cycloaddition/Nazarov cyclization of (E)-2-arylidene-3-hydroxyindanones with eneynes under the dual catalysis of an acid and a transition metal for the synthesis of indanone-fused benzo [cd]azulenes in one-pot route.…”

Annulations involving 1-indanones to access fused- and spiro frameworks

“…In 2020, Zhou et al successfully designed and synthesized dibenzo[ a , f ]azulene-12-one derivatives 24 from readily available o -propargyl alcohol benzaldehydes 22 and alkynes 4 with the help of p -TsOH catalyst ( Scheme 8 ). 39 Various tertiary/secondary aryl propargyl alcohols participated in the annulation process. The cycloaddition reaction was relevant for both terminal as well as internal alkynes with a variety of substituents such as alkyl, eater, aryl, heteroaryl, etc.…”

Transition‐Metal‐Free Synthesis of 1‐Indanone Skeleton: A Brief Update

“…The authors also accomplished the formal [5+2]‐cycloaddition of alkynes 23 with 3‐hydroxy indanones 18 , generated in situ from ortho ‐propargyl alcohol benzaldehydes 17 , that could efficiently construct the dibenzo[a,f]azulene‐12‐ones 24 [33] . Among various Brønsted acid catalysts (such as TfOH, HNTf 2 and TFA, etc.)…”