# Gold-Catalyzed Cyclizations of 4‑Alkyl-2-yn-1-yl (Oxy)cyclohexa-2,5-dien-1-ones (1) to Develop Two Cyclizations via π‑Alkyne versus π‑Allene Activations

## TL;DR

This paper describes two new gold-catalyzed reactions that convert a specific compound into different products through distinct chemical pathways.

## Contribution

The study introduces two novel gold-catalyzed cyclization pathways for a specific compound via π-alkyne and π-allene activations.

## Key findings

- The π-allene route produces 2-substituted 3-formylbenzofurans via a [3.3] Claisen rearrangement mechanism.
- The π-alkyne route stereoselectively forms C3,4-fused tetrahydrobenzofuran-5(4H)-ones using PhNH2 as a cocatalyst.
- DFT calculations confirm the proposed mechanism involving water as a key player in the π-allene pathway.

## Abstract

This work reports two new gold-catalyzed cyclizations
of 4-alkyl-2-yn-1-yl
(oxy)­cyclohexa-2,5-dien-1-ones (1) via gold−π-allene
versus gold−π-alkyne routes, The π-allene route
involves a [3.3] Claisen rearrangement of 1-alloxyallene intermediates
to enable a 1,3-group migration, ultimately affording 2-substituted
3-formylbenzofurans (2). Density functional theory (DFT)
calculations support this proposed mechanism in which water plays
a key role. An alternative π-alkyne route contains cocatalyst
PhNH2 (10 mol %), leading to the formation of C3,4-fused tetrahydrobenzofuran-5­(4H)-ones (3) stereoselectively.