A catalytic [1,3] O-to-C rearrangement from enyne-ethers was developed for the rapid synthesis of diverse bridged bicyclic systems. In this reaction, a vinyl oxonium intermediate, generated in situ from enyne-ether, was the precursor for the [1,3] O-to-C rearrangement. This versatile protocol represents the first example of catalytic [1,3] O-to-C rearrangement based on ring-expansion strategy, enabling efficient access to bridged bicyclic scaffolds.

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The dearomative functionalization of aromatic compounds represents a fascinating but challenging transformation, as it typically needs to overcome a great kinetic barrier. Here, a catalyst-free dearomative rearrangement of o-nitrophenyl alkyne is successfully established by leveraging the remote oxygen transposition and a weak N-O bond acceleration. This reaction features high atom-, step- and redox-economy, which provides a divergent entry to a series of biologically important benzazepines and bridged polycycloalkanones. The reaction is proposed to proceed through a tandem oxygen transfer cyclization/(3 + 2) cycloaddition/(homo-)hetero-Claisen rearrangement reaction. The resulting polycyclic system is richly decorated with transformable functionalities, such as carbonyl, imine and diene, which enables diversity-oriented synthesis of alkaloid-like polycyclic framework.

An unprecedented Lewis acid-catalyzed cascade 1,3-rearrangement/Friedel–Crafts cyclization of propargyl acetates is developed for the construction of polycyclic bridged indene derivatives.

Ag old (I)-catalyzed reactiono fe nyne-etherst o rapidly construct oxa-bridged compoundsv ia at andem 1,2-acyloxy migration/intramolecularo xonium formation/ 1,2-rearrangement process was reported. The reaction was shown to be robust with aw ide range of substitution patterns tolerated to provide the corresponding oxygen-containing bridged products in good to excellent yields.Developing general and efficient methods for the construction of structurally diverse and complex polycyclic skeletons is important for natural products synthesis and lead discovery. [1] Oxygen-bridged bicyclic skeletons are ubiquitous structures in aw ide range of synthetic andn atural products, [2] such as Balsamiferine J, [2h] Englerin B, [2e] WaltherioneC, [2f] Mollanol A, [2g] Coutistatin A [2k] (Scheme 1). Highlye fficient construction of these oxa-bridged skeletons is one of the most important themes in organic synthesis. Much effort hasbeen made to de-Scheme1.Representative natural products with oxa-bridged bicyclic skeletons.Scheme2.Proposed gold-catalyzed propargyle ster rearrangements and further transformations.