Synthesis of phthalides and 3,4-dihydroisocoumarins using the palladium-catalyzed intramolecular benzannulation strategy.
A novel method for the synthesis of phthalides and 3,4-dihydroisocoumarins via the palladium-catalyzed intramolecular benzannulation of bis-enyne and enyne-diyne systems is described. Various kinds of substituted phthalides 9 and 17 and 3,4-dihydroisocoumarins 19 were synthesized from 8, 16, and 18, respectively, in moderate to excellent yields. The benzannulation reaction proceeded chemoselectively to give the corresponding fused ring compounds A without the formation of the regioisomeric products B (eq 6). Furthermore, this methodology was applied to the synthesis of biologically active 3-n-butylphthalide 23.
Kawasaki
Taishi
T
Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
Saito
Shinichi
S
Yamamoto
Yoshinori
Y