An efficient and practical process for the synthesis of ramelteon 1, a sedative-hypnotic, is described. Highlights in this synthesis are the usage of acetonitrile as nucleophilic reagent to add to 4,5-dibromo-1,2,6,7-tetrahydro-8H-indeno[5,4-b]furan-8-one 2 and the subsequent hydrogenation which successfully implement four processes (debromination, dehydration, olefin reduction, and cyano reduction) into one step to produce the ethylamine compound 13where dibenzoyl-l-tartaric acid is selected both as an acid to form the salt in the end of hydrogenation and as the resolution agent. Then, target compound 1 is easily obtained from13 via propionylation. The overall yield in this novel and concise process is almost twice as much as those in the known routes, calculated on compound 2.
A Novel and Practical Synthesis of Ramelteon
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