No abstract

The regioselective ipso-formylation of electron-rich, 3,4-push-pull-substituted 2-chlorothiophenes under Vilsmeier-Haack conditions was performed in good yields. The synthetic scope of this new reaction was explored using various halothiophenes, chloroanilines, and 1-methyl-3-chloroindole. In comparison with their structural C-H analogs the chlorinated thiophenes, anilines, and the indole proved to be less reactive toward electrophilic attack by chloromethyleniminium salts.

No abstract

The unique synthesis of 3‐amino‐4‐nitrothiophenes 2 provides easy access to reference species of a new family of push‐pull substituted thiophenes. The chemoselective modification of 2 into suitable derivatives was accomplished by selective S‐oxidation of the vinylsulfanyl unit, followed by substitution of the vinylsulfinyl group of 3 by nucleophiles. Dihalothiophenes were formed this way in very good yields. A subsequent selective dehalogenation at the 2, 5 or 2 and 5 positions also proved feasible, and the push‐pull unit was untouched. The new 2,5‐dihalothiophenes could be interesting monomers for conducting polymers.

Reaction of gem-dichloronitroalkenes with base leads to the formation of chlorinated nitrile oxides, probably via a cyclic intermediate. The 1,3-dipoles can be trapped with alkenes to give dihydroisoxazoles with a chlorinated side chain in 3-position. This novel synthetic method is fairly general.