Diazo compounds have emerged as one of the most versatile and useful reagents in modern synthetic organic chemistry. Specially, applications of diazo chemistry to the preparation of biologically interesting and active compounds are increasing day by day. Natural products bearing -substituted -haloenones, furopyrimidinediones, furopyranones and indene skeletons are widely found in nature. They have been found to possess a variety of biological activities such as antiproliferative, cytotoxic agents, antimicrobial, antimalarial, antitumor, anticancer, antibacterial, and fungicidal properties. Due to the importance of their biological activities and properties, this research work aims at developing novel and efficient synthetic protocols for the construction of biologically interesting diverse organic molecules such as -substituted -haloenones, furo[2,3-d]pyrimidinediones and thioxofuro[2,3-d]pyrimidineones, furo[2,3-b]pyran-6-ones and functionalized indene derivatives using diazo compounds as starting materials. These newly developed synthetic protocols are expected to be widely used for the construction of pharmacologically active molecules and heterocyclic compounds.