Regio- and Stereospecific Hydrative Cloke–Wilson Rearrangement

Abstract

The Cloke−Wilson rearrangement of unsymmetrical βdiketone-derived cyclopropanes inevitably yields a mixture of two 4acylated 2,3-dihydrofuran regiomers. By using alkynes as masked acyls, Tf 2 NH-promoted Cloke−Wilson rearrangement of polysubstituted 1-(1alkynyl)cyclopropyl ketones followed by alkyne hydration is described, regioselectively affording 2,3-dihydrofurans bearing 4-acyls nonequivalent to that involved in the Cloke−Wilson rearrangement. The 2,3dihydrofuran rings with cis 2,3-diaryls are unexpectedly more stable than their trans diastereomers under the reaction conditions, guaranteeing the regiospecificity of this hydrative Cloke−Wilson rearrangement with high fidelity.

Intramolecular 1,2-Aroyl Migration in Spiro Donor–Acceptor Cyclopropanes: Formation of 1,4-Naphthoquinones and 1-Naphthols as Ring-Expansion Products

“…Generally, when treated with Lewis acids, DACs form transient 1,3-zwitterionic intermediates by ring-opening, which participate in annulations to give cyclic products, combine with nucleophiles or radicals to give mono- or difunctionalized products, or undergo rearrangements to give ring-expansion products . Among the various rearrangement reactions of DACs, the Cloke–Wilson rearrangements of cyclopropyl ketone to dihydrofuran, cyclopropyl imine to pyrroline, cyclopropyl ester to γ-butyrolactone, cyclopropyl amide to γ-butyrolactam, and other rearrangements such as nitrocyclopropane to isooxazoline- N -oxide involve the formation of new C–O or C–N bonds in the products (1,3-migration of carbon atom). Similarly, the vinylcyclopropane to cyclopentene rearrangement, homo-Nazarov rearrangement of cyclopropyl vinyl/aryl ketones to cyclohexenones/α-tetralones, and other rearrangements involve the formation of a new C–C bond (1,3- or 1,4-migration).…”

Catalytic Intramolecular Ketone Haloacylation Enabled Stereoselective Heterolytic Cleavage of Cyclopropyl Ketones with Enhanced Reactivity and Regioselectivity beyond Electronics

“…α-Alkynyl ( 1ca and 1cb ) and ring-fused ( 1da ) DACs were also suitable for this 1,5-haloacylation reaction (Scheme ). Notably, the internal alkyne in 1ca survived the reaction, while the terminal ethynyl group in 1cb was hydrochlorinated under reaction conditions. Although the palladium catalyst failed to catalyze the reaction of 1y with an alkynyl donor, it is effective for 1ca and 1cb with alkynyl acceptors.…”