A Facile Intramolecular Cyclization of 4-Diazomethylcoumarins. A Convenient Route to Benzopyrano[3,4-c]pyrazol-4(3H)-ones

Abstract

The 7-substituted 4-diazamethylcoumarins 2 as the , stable aryldiazomethanes were rapidly transformed into their cyclized isomers, benzopyranoI3.4-clpyrazol-4(3H)-ones 2 in high yields in refluxing toluene. 1We have recently reported the preparations of the 7-substituted 4-diazomethylcoumarins Z as a new type of stable aryldiazomethanes which are potentially useful fluorogenic reagents for acids andIn this communication we wish to report facile thermal cyclization of Z leading to the formation of the benzopyrano 13,4-cl pyrazol-4 (3H) -ones 2.