Synthesis of multi-functionalized benzofurans through the condensation of ninhydrin and phenols using SSA as a recyclable heterogeneous acid catalyst
A simple and efficient one-pot methodology has been developed for the synthesis of biologically important multi-functionalized 3-(2$$^{\prime }$$′-hydroxyaryl)-2-(2$$^{\prime }$$′-carboxyphenyl)benzofurans using silica sulfuric acid (SSA) as a heterogeneous acid catalyst in DMF medium. The significant advantages of this methodology are the use of SSA as a recyclable solid acid catalyst, operational simplicity, easy availability of the starting materials, and good yield of the products with high atom-economy.
Novel Non‐toxic and Non‐hazardous Solvent Systems for the Chemistry of Indoles: Use of a Sulfone‐containing Brønsted Acid Ionic Liquid Catalyst in Butyl Acetate
Dipolar and aprotic solvents are often required in acid‐catalyzed reactions, however, many of them are listed in solvent selection guides as not‐recommended due to their toxicity or explosivity. A catalytically functionalized ionic liquid, namely a sulfone‐containing imidazolium‐based Brønsted acid ionic liquid, was synthesized. It alleviates the detrimental effect of classical dipolar aprotic solvents because this ionic liquid integrates the function of a dipolar aprotic solvent able to stabilize carbocation intermediates and the activating effect of a strong Brønsted acid on electrophiles. The use of this tailor‐made ionic liquid was exemplified in some transformation reactions of indoles, which proceeded with high yield and selectivity using a green and an industrially acceptable solvent, butyl acetate. The recyclability of the ionic liquid catalyst was also demonstrated.
Palladium catalyzed oxycarbonylation of 4-penten-1,3-diols: efficient stereoselective synthesis of cis 3-hydroxytetrahydrofuran 2-acetic acid lactones
Abstract cis 3-Hydroxytetrahydrofuran acetic acid lactones have been prepared selectively and in high yield by an intramolecular palladium catalyzed oxycarbonylation of 4-penten-1,3-diols under mild conditions (room temperature, 1 atm of CO).