2-Nitrobenzofuran and 3-Nitrobenzofurans as dienophiles in Polar Diels-Alder Reactions. Theoretical studies using DFT Methods

2- and 3-nitrobenzofurans are studied in polar thermal Diels-Alder reactions whit normal electron demand using several and structural different dienes. A very strong electron-acceptor group, such as nitro group, push the dienophilic character of these heterocyclic compounds and owing to this substituent is easily extruded under thermal conditions make this reaction sequence a simple method of organic compound's families with heteroatom rings preparation. This work is specifically concerned with theoretical studies using DFT methods. 2-nitrobenzofuran and 3-nitrobenzofuran react as dienophile against isoprene, 1-trimethylsilyloxy-1,3-butadiene, the Danishesfky diene and the Rawal's diene, taking part in a normal demand DA cycloaddition reactions. These reactions could be considered a domino process that is initialized by a polar D-A reaction, and the latter concerted elimination of nitrous acid from the [4 + 2] cycloadduct yields the corresponding dibenzofurans.