An Approach to the Synthesis of Pyrimido[b]azepines via Ruthenium-Catalyzed Ring-Closing Metathesis

A highly efficient approach to the synthesis of a series of pyrimido[b]azepines has been developed with 5-allyl-2,4,6-trichloropyrimidine as the starting material in six or seven steps via a ring-closing metathesis (RCM) reaction. The absolute configuration of the key intermediate pyrimido[4,5-b]azepine was ascertained by X-ray crystal structure analysis.