A Mild and Environmentally Benign Synthesis of Tetrahydrobenzo[b]pyrans and Pyrano[c]chromenes Using Pectin as a Green and Biodegradable Catalyst

Pectin was applied as a green and biodegradable catalyst for the one-pot three-component synthesis of tetrahydrobenzo[b]pyrans and pyrano[c]chromenes, from the condensation between aromatic aldehydes, malononitrile, and dimedone or 4-hydroxycumarine at ambient temperature. This protocol has many advantages such as mild conditions, high yields, environmental benignity, simple work-up procedures, short reaction time, as well as the use of a natural, easily accessible, convenient handling, and inexpensive catalyst. Another advantage of this method is that the products do not require further purification such as column chromatography.