10.1039/c39860000784
The research explores a new route to synthesizing indoles through the deoxygenation of ortho-nitrostyrenes using carbon monoxide and metal carbonyl catalysts. The purpose is to develop a more selective and efficient method for constructing the indole nucleus under non-acidic conditions, which is of significant academic and industrial interest. Key chemicals used include Fe(CO)5, Ru3(CO)12, and Rh6(CO)16 as catalysts, along with various ortho-nitrostyrene substrates prepared via a modified Wittig reaction. The study found that Fe(CO)5 was the most selective catalyst, yielding primarily indoles with some side products like amines and quinolones. The method offers advantages over traditional deoxygenation methods, such as better selectivity and a simpler work-up procedure. The research also isolated a non-catalytically active rhodium complex during the synthesis, providing insights into the catalytic mechanism.