Cycloisomerization of Allene–Enol Ethers under Bi(OTf)₃ Catalysis

Abstract

The cycloisomerization of allene-enol ethers under Bi(OTf)3 catalysis was developed as a novel "atom-economic" tool for accessing interesting functionalized cyclopentene rings. Bi(OTf)3 was shown to promote selectively the activation of the enol ether moiety of the substrate. This catalytic methodology was further extended to the synthesis of dihydrofuran and oxaspirocycle derivatives.

Cyclisation Reactions Involving Alkyl Enol Ethers

“…[36] Recently, Duñach et al developed a Lewis superacid-catalysed cycloisomerisation of allene-enol ethers (Scheme 16). [37] The enol ether was found to be activated preferentially by a catalytic amount of Bi(OTf) 3 in the presence of a tethered allene. Electro-philic activation of the enol ether was followed by nucleophilic 5-exo-dig addition of the allene to the intermediate oxocarbenium species.…”

Stereocontrolled Cascade Cyclisation of Campholenic Enol Ether Derivatives: En Route to Vetiver‐Scented Spiroxides

“…Recently, we developed new cyclisation reactions involving functionalised enol ethers displaying a tertiary alcohol motif and an alkene or an allene function. Specifically designed enol ethers were shown to undergo tandem cyclisations under acidic conditions, leading to the formation of oxanorbornane spirocyclic diethers (Scheme ) …”

“…[4] In this area, bismuth(III) triflate is known for its wide applicability to the activation of various chemical functions in cyclisation reactions. [5] Recently, we developed new cyclisation reactions involving functionalised enol ethers displaying a tertiary alcohol motif and an alkene [6] or an allene [7] function. Specifically designed enol ethers were shown to undergo tandem cyclisations under acidic conditions, leading to the formation of oxanorbornane spirocyclic diethers (Scheme 1).…”

Synthesis and olfactory evaluation of allylic α‐quaternary ether ketones

“…Special attention is hereby given to the scalability, robustness, and operational simplicity of the experimental procedure. The introduction of oxygen functionality by means of an enol ether has been one of our more recent research interests, and has led to the discovery of a range of interesting odoriferous molecules …”

“…13,14 Special attention is hereby given to the scalability, robustness, and operational simplicity of the experimental procedure. The introduction of oxygen functionality by means of an enol ether has been one of our more recent research interests, 15,16 and has led to the discovery of a range of interesting odoriferous molecules. [17][18][19] Herein, we report the olfactory notes of α-quaternary, oxygenated β,γ-unsaturated ketones prepared via a catalytic rearrangement of diallyl alcohols derived from α,β-unsaturated ketones and enol ethers.…”