Microwave-assisted synthesis of novel hetero[5]helicene-like molecules and coumarin derivatives.

A concise and efficient approach to design and synthesize hetero[5]helicene-like molecules and coumarin derivatives is reported. Intriguingly, using the same catalyst (silica sulfuric acid), and a different solvent and reaction temperature, the reaction selectively afforded hetero[5]helicene-like molecules 3 or coumarin derivatives 4. Product 4 has a highly planar geometry, and product 3 can be regarded as hetero[5]helicene-like because of its helical conformation.