As one of the most fundamental rearrangement reactions, the classical Piancatelli reaction mainly relies on the use of α-furylcarbinols and is initiated by an acid-promoted dehydroxylation process and limited to a two-component manner. In this work, the first asymmetric radical-mediated three-component Piancatelli-type rearrangement of furylalkenes with diverse carbon-centered radical precursors and anilines is developed via the combination of copper­(I) or photoredox catalysis with chiral Brønsted acid and unchiral Lewis acid catalysis. This protocol features a wide substrate scope and high functional group tolerance and provides expedient access toward a broad spectrum of densely functionalized fluoroalkyl-containing cyclopentenones bearing α-quaternary carbon stereocenters in high yields with high enantioselectivities and diastereoselectivities (>70 examples, up to 95% yield, 96% ee, and >20/1 dr). The synthetic utility has been demonstrated by product derivations and applying onto the late-stage functionalization of valuable drug targets or natural products. Mechanistic studies revealed that the diastereoselectivity of the rearrangement reaction was controlled by Dy­(III)-accelerated Z/E isomerization of the Piancatelli intermediates and the chiral Brønsted acid-catalyzed 4π-electrocyclization of pentadienyl carbocation intermediates was both a rate- and enantio-determining step.

The first Lewis acid and chiral Brønsted acid cooperatively catalyzed asymmetric cascade ring opening/aza-Piancatelli rearrangement reaction of furyl-substituted donor–acceptor cyclopropanes is achieved, enabling the construction of functionalized aminocyclopentenones bearing α-quaternary carbon stereocenters in high yields with excellent enantio- and diastereoselectivities under remarkably low catalyst loading of 0.2–1.2 mol %.

The Piancatelli reaction, which is the rearrangement of 2-furylcarbinol to cyclopentenone, involves a key furanoxonium ion intermediate and a furan ring opening-4π electrocyclization process. In recent years, the original oxa-Piancatelli reaction has been extended to a large family of aza- and carbo-Piancatelli reactions and related cascade processes, providing a powerful platform for the construction of diverse functionalized cyclopentenones and polycyclic cyclopentanones. Meanwhile, chiral Brønsted/Lewis acid based catalytic asymmetric approaches to Piancatelli reactions have also been achieved for the assembly of highly valued chiral cyclopentenone scaffolds. In this short review, we present an overview of the recent developments in these areas and focus primarily on reports published in the last five years.1 Introduction2 Diastereoselective Oxa-, Aza- and Carbo-Piancatelli Reactions3 Diastereoselective Cascade Piancatelli Reactions4 Asymmetric Piancatelli Reactions and Related Cascade Processes5 Miscellaneous Furanoxonium Ion-Based Rearrangements6 Conclusion