Reactions of 3-(1-Hydroxyalkyl)phthalides with Acids: Synthesis of (Z)-3-Alkylidenephthalides and 3-Alkyl-8-hydroxyisocoumarins.
A new acid-catalyzed method for the synthesis of (Z)-3-butylidenephthalides 5 and a novel and general route to 3-alkyl-8-hydroxy/methoxyisocoumarins 6-8 from phthalides 9 is described. The hydroxyphthalides 4 and 10 were obtained by condensation of the phthalide anion with butyraldehyde and acetaldehyde. Reaction of hydroxyphthalides 4 with a mixture of orthophosphoric acid and formic acid gave the (Z)-3-butylidenephthalides 5, while the hydroxyphthalides 4 and 10 on reaction with p-toluenesulfonic acid provided the 3-alkylisocoumarins 6-8. The present approaches permit variation of the 3-substituent in isocoumarin and the pattern of functionalization on the aromatic rings of both isocoumarins and alkylidenephthalides.
Mali
Raghao S.
RS
Department of Chemistry, Garware Research Centre, University of Pune, Pune 411 007, India.
Babu
Kantipudi N.
KN