Development of a Scaleable Synthesis of a Partial Nicotinic Acid Receptor Agonist

A practical and efficient synthesis of 1,4,5,6-tetrahydro-3-(1H-tetrazol-5-yl)cyclopenta[c]pyrazole, 1, is described. A new one-pot process has been developed, starting from the commercially available 1H-tetrazole-5-carboxylic acid-ethyl ester sodium salt which is reacted in a pseudo-Claisen condensation reaction with cyclopentanone, followed by the addition of hydrazine.