Synthesis of (Het)aryl 2-(2-hydroxyaryl)cyclopropyl Ketones

Extended Corey–Chaykovsky reactions: transformation of 2-hydroxychalcones to benzannulated 2,8-dioxabicyclo[3.2.1]octanes and 2,3-dihydrobenzofurans

We report the divergent synthesis of benzannulated 2,8-dioxabicyclo[3.2.1]octanes and 2,3-dihydrobenzofurans using the concept of extended Corey–Chaykovsky reactions.

Protic Ionic Liquid as Reagent, Catalyst, and Solvent: 1-Methylimidazolium Thiocyanate

We propose a new concept of the triple role of protic ionic liquids with nucleophilic anions: a) a regenerable solvent, b) a Brønsted acid inducing diverse transformations via general acid catalysis, and c) a source of a nucleophile. The efficiency of this strategy was demonstrated using thiocyanate-based protic ionic liquids for the ring-opening of donor-acceptor cyclopropanes. A wide variety of activated cyclopropanes were found to react with 1-methylimidazolium thiocyanate under mild metal-free conditions via unusual nitrogen attack of the ambident thiocyanate ion on the electrophilic center of the three-membered ring affording pyrrolidine-2-thiones bearing donor and acceptor substituents at the C(5) and C(3) atoms, respectively, in a single time-efficient step. The ability of 1-methylimidazolium thiocyanate to serve as a triplex reagent was exemplarily illustrated by (4+2)-annulation with 1-acyl-2-(2-hydroxyphenyl)cyclopropane, epoxide ring-opening and other organic transformations.