Nitro-pyridines as Dienophiles in Polar Diels-alder Reactions. A DFT Theoretical Study

3-nitropyridine and 4-nitropyridine N-oxide were theoretically studied, acting as dienophiles in the Diels-Alder reaction with different dienes. It was observed that both azacycles would suffer the cycloaddition reaching the quinoleine derivatives. Regioselectivity was predicted.The mechanism reaction was also analyzed observing that there is only one asymmetric and asynchronous transition state between the reactants and the primary cycloadduct when isoprene is the diene involved, and two when 1-methoxy-1,3-butadiene and Danishefsky\'s diene were used.