Rapid Synthesis of Fused Oxabicycles through the Molecular Rearrangement of Spirocyclic Ethers

The Piancatelli rearrangement of non-symmetrical furan-2,5-dicarbinols for the synthesis of highly functionalized cyclopentenones

Piancatelli rearrangement on substituted non-symmetrical furan-2,5-dicarbinols has been developed using an effective combination of microwave activation and Lewis acid catalyst.

A chiral cobalt(ii) complex catalyzed enantioselective aza-Piancatelli rearrangement/Diels-Alder cascade reaction

A chiral N,N′-dioxide/cobalt(ii) complex catalyzed highly diastereoselective and enantioselective tandem aza-Piancatelli rearrangement/intramolecular Diels–Alder reaction has been disclosed. Various valuable hexahydro-2a,5-epoxycyclopenta[cd]isoindoles bearing six contiguous stereocenters have been obtained in good yields with excellent diastereo- and enantio-selectivities from a wide range of both readily available 2-furylcarbinols and N-(furan-2-ylmethyl)anilines.

An asymmetric aza-Piancatelli rearrangement/Diels–Alder cascade reaction between 2-furylcarbinols and N-(furan-2-ylmethyl)anilines was realized by using a chiral N,N′-dioxide/cobalt(ii) complex catalyst.

The Piancatelli reaction and its variants: recent applications to high added-value chemicals and biomass valorization

The conversion of furfuryl alcohols by the Piancatelli reaction (and its C- and N-variants) provided highly functionalized cyclopentenones (intermolecular) and spirocycles (intramolecular).

Intramolecular etherification and polyene cyclization of π-activated alcohols promoted by hot water

Hot water, acting as a mildly acidic catalyst, efficiently promoted intramolecular direct nucleophilic substitution reactions of unsaturated alcohols with heteroatom or carbon nucleophiles. In a mixed solvent of water and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), polyene cyclizations using allylic alcohols as initiators gave the desired cyclized products, and in neat HFIP, a tricyclization reaction gave a tetracyclic product in 51% chemical yield.

The versatility of furfuryl alcohols and furanoxonium ions in synthesis

Substituted furfuryl alcohols are extraordinarily versatile starting materials in synthesis. They are precursors to furanoxonium ion intermediates which are implicated in the Piancatelli reaction (leading to 2-cyclopentenones) and in the synthesis of novel dihydrofuran-based exo enol ether/cyclic ketal natural products. They are also intermediates in a recently discovered (4+3) cycloaddition reaction with 1,3-dienes leading to furan ring-fused cycloheptenes. Here we provide a perspective on recent developments in these areas of synthesis, alongside recent applications of the Achmatowicz reaction and [5+2] cycloaddition reactions of the resulting oxidopyrylium ions.