Piancatelli rearrangement

An intramolecular aza-Piancatelli rearrangement that constructs a fully substituted carbon centre bearing a nitrogen atom and a spirocyclic ring system in a single operation has been catalysed by dysprosium (Ill)triflate. The azaspirocycles are formed exclusively as the irons diastereomer, consistent with a electrocyclization (Scheme 99). ... 

Intramolecular Piancatelli rearrangement of 2-furylcarbinols with alcohols catalyzed by dysprosium(III) triflate led to oxaspirocycles (130L476). 

The aza-Piancatelli rearrangement of furans was used to form a functionalized cyclopentenone.This reaction allows the formation of congested vicinal stereogenic centers through a 4Jt-electrocyclization process (13OL3250). 

A stereoselective synthesis of spirocyclic ethers via an intramolecular Piancatelli rearrangement has been reported (Scheme 169). " ... 

The aza-Piancatelli rearrangement of furylcarbinols and anilines can be triggered by Dy(OTf)3 to give 5-substituted-4-aminocyclopentenones with exclusive trans-selectivity (eq 6). This rearrangement is also proposed to terminate in a conrotatory 4it C-C bond-forming electrocyclization. 

In addition to the intermolecular aza-Piancatelli rearrangement, Dy(OTf)3 has been found to catalyze the intramolecular aza-Piancatelli rearrangement that provides access to nitrogen spiro-cycles (eq 7). ... 

Much of the chemistry of Dy(OTf)3 has been focused on transformations in the presence of basic nitrogen groups however, it is not limited to such reactions. It has been shown that Dy(OTf)s catalyzes the intramolecular oxo-Piancatelli rearrangement in toluene to form spirocyclic ethers (eq 8). ... 

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