One‐Pot Multicomponent Synthesis of Novel Spiro‐(1,8)‐Naphthyridine Derivatives in PEG‐400

Abstract

A one‐pot multi‐component pathway is reported to synthesize novel spiro‐(1,8)‐naphthyridine derivatives in good to excellent yields via the condensation reaction of isatin derivatives, malononitrile dimer and enamine derivatives. In polyethylene glycol‐400 at 80 °C, more than 30 novel products of spiro‐(1,8)‐naphthyridines were synthesized up to 95 % yields with only water as a by‐product. Separation of the products was performed efficiently and no additional operation was needed for purification of the products, except that, in some cases, recrystallization was done. Moreover, some new spiro‐dihydropyrimidines were efficiently synthesized when malononitrile (or methyl/ethyl‐2‐cyanomalonate) was employed instead of enamines.