A process for the synthesis of 2-(4-chlorophenyl)-2-hydroxy-N-(3-methoxy-4-(prop-2-yn-1-yloxy)phenethyl)acetamide, a key intermediate of Mandipropamid The present invention provides an improved method for the preparation of building blocks 2-(4-chlorophenyl)-2-hydroxy-N-(3-methoxy-4-(prop-2-yn-1-yloxy)phenethyl)acetamide, a key intermediate for the synthesis of Mandipropamid. An efficient, safe, cost-effective method for the preparation of Mandipropamid is developed. The method involves simple Nitro-aldol reaction, LAH reduction and mild Amidation reaction for synthesizing key intermediate 2-(4-chlorophenyl)-2-hydroxy-N-(3-methoxy-4-(prop-2-yn-1-yloxy)phenethyl)acetamide (E). The current synthesis method of the invention has relatively simple operation, mild reaction conditions, high yield and a simple process with, a yield up to 90%. Subsequent product purification of this method uses filtration and crystallization methods and easy column chromatography separation. This approach is highly effective and scalable, contributing to both atom and step economy in the process Therefore, the research of its synthetic process has a wide range of applications from the drug development and material synthesis point of view.