Water Extract of Lemon (WEL) as a Promoter: Green and Regioselective Synthesis of Alkyl‐4‐(1 H ‐indol‐3 yl)‐2‐alkyl‐4 H ‐chromene‐3‐carboxylates Using 4 H ‐chromenes and Indoles

An efficient, simple, green, regioselective and catalyst‐free synthesis of alkyl‐4‐(1 H ‐indol‐3yl)‐2‐alkyl‐4H‐chromene‐3‐carboxylates is disclosed by employing indoles and substituted chromene derivatives under mild reaction condition. This is a novel green methodology, simple, eco‐friendly and easy to operate. Biomass‐derived catalyst Water Extract of Lemon (WEL) was used as a promoter for this procedure. The methodology could be applicable for cost‐effective large scale production of alkyl‐4‐(1 H ‐indol‐3yl)‐2‐alkyl‐4 H ‐chromene‐3‐carboxylates in good to excellent yield.