Synthesis of Pyrano[4,3‐d]pyrimidine Derivative and Its Behaviour towards Nitrogen Nucleophiles and Active Methylenes

Pyrano4,3‐d]pyrimidine derivative 3 was prepared by reaction of chlorocarbonyl isocyanate 1 with enaminonitrile 2 . Compound 3 reacted with nitrogen nucleophiles 4a‐f to afford 2‐substituted pyrido4,3d]pyrimidine 5–8 , pyrimidoi]1,5a‐diaza‐9‐oxafluorene 9 and pyrimidoi]5a‐aza‐9‐thiafluorene 10 derivatives. Also, compound 3 reacted with active methylene compounds 4j to yield pyrimidine derivatives 14–16 which on reaction with EtONa 4k afforded 1,5,7‐triaza‐10‐oxaphenanthrene derivatives 17–19 .