CHEMISTRY OF PHOSPHORUS YLIDES 9.¹ REACTIONS WITH PHOSPHACUMULENES III.² SYNTHESIS OF BENZODIPYRANS FROM THE REACTION OF KETENYLIDENE- AND THIOKETENYLIDENETRIPHENYLPHOSPHORANE WITH FORMYL BENZOPYRAN DERIVATIVES

Abstract

When 6-formyl-7-hydroxy-5-methoxy-2-methylbenzopyran-4-one (1a), was reacted with ketenylidene(2a) and thioketenylidenetriphenylphosphorane (2b), the corresponding 5-methoxy-8-methyl-2,6-dioxo 2H, 6H-benzo[1,2-b:5,4-b′]dipyran (4a) and its thio analogue (4b), were obtained respectively. The structure of the new benzodipyrans (4) were confirmed on the basis of elemental analysis and spectral studies. Moreover, the pyrazole derivatives (5), were obtained when compounds (4) were allowed to react with hydrazine hydrate.

Key Words:

• Intramolecular Wittig reaction
• benzodipyrans
• pyrazoles.