Catalyst-Free Site Selective Hydroxyalkylation of 5-Phenylthiophen-2-amine with α-Trifluoromethyl Ketones through Electrophilic Aromatic Substitution

An original and effective approach for achieving trifluoromethyl hydroxyalkylation of 5-phenylthiophen-2-amine using α-trifluoromethyl ketones is described. In the last few years, reaction of Friedel-Crafts had been widely used to realize hydroxyalkylation on heterocycles such as indoles or thiophenes by means of Lewis acid as catalyst. Additionally, amine functions are rarely free when carbonyl reagents are used because of their tendency to form imines. This is the first time that a site-selective electrophilic aromatic substitution on C₃ atom of an unprotected 5-phenylthiophen-2-amine moiety is reported. The liberty to allow reaction in neutral conditions between free amine is valuable in a synthesis pathway. The reaction proceeds smoothly using an atom-economical metal-and catalyst-free methodology in good to excellent yields. A mechanism similar to an electrophilic aromatic substitution has been proposed.

Synthesis of N,N-disubstituted 2-aminothiophenes by the cyclization of gem-difluoroalkenes with β-keto thioamides

A novel and effective method for the construction of highly functionalized aminothiophenes via the cyclization of gem-difluoroalkenes with β-keto tertiary thioamides is described.

Direct synthesis of polysubstituted 2-aminothiophenes by Cu(II)-catalyzed addition/oxidative cyclization of alkynoates with thioamides

A facile and direct synthetic method was developed for the construction of structurally important 2-aminothiophenes in moderate to excellent yields (up to 91%), via Cu(II)-catalyzed addition/oxidative cyclization of readily available thioamides with alkynoates under an air atmosphere.