An Improved Synthetic Method for the Preparation Of Indole-3-Carboxylic Acid Derivatives: Useful Key Intermediate for the Synthesis of Several Biologically Active Molecules Including Tropisetron

• A simple, feasible, straightforward, economically viable, operationally simple one-pot process;
• The synthesis method has a relatively simple operation, mild reaction
• conditions, high yield and a simple process with moderate to good yield;
• The method is less time consuming compared to existing methods;
• Isatin has been used as a starting material which is cheaper than Indole / other designed starting materials;
• No reducing agent, no transition metal, Lewis acid or costly reagents has been used.  
• The subsequent product separation process is very simple and it is useful for small-scale laboratory preparation as well as large-scale industrial production.
• Subsequent product separation method is safer with a better yield compared to existing methods.
• The process has been used to prepare commercially available drug such as Tropisetron in good yield and several other drugs such as Dolasetron etc can be made with low cost, high yield and suitable for industrial production.
• The method is cost-effective compared to existing methods.
• The conversion happens at aerial pressure and it is operationally simple, economically viable, and effective for industrial preparation.
• Unique features of this reaction are the utilization of solvent (DMSO /DMSO-d6) as a reactant and the formation ICA derivatives in good to excellent yields without treating any reducing agents or transition metals.

The invention relates to a synthetic method for the preparation of building block indole-3-carboxylic acid (ICA) derivatives used as a key starting material to produce several artificial drugs.

The process has been used to prepare commercially available drug such as Tropisetron in good yield and several other drugs such as Dolasetron etc can be made with low cost, high yield and suitable for industrial production.