JOURNAL OF THE CHINESE
CHEMICAL SOCIETY
Yttrium Catalyzed Pechmann Synthesis of Coumarins
variety of coumarins were obtained in good to excellent
yields in short reaction times.
In a general experimental procedure, b-Ketoester (1
mmol) was added to a mixture of substituted phenol (1
Coumarin 1a was synthesized in 92% yield for 45
3 3 2
mmol) and Y(NO ) ×6H O (0.0392 g, 10 mol%) in a screw-
min (monitored by TLC CCl
4
– ethylacetate 5:1). It was
cap vial. The reaction mixture was stirred in a preheated oil
bath (90 °C). After the completion of the reaction, the solid
product was suspended in water (20 mL). The resulting
crude product was filtered off and recrystallized from hot
EtOH to give a white crystalline solid.
characterized by IR, NMR and other spectral data Simi-
larly, resorcinol was treated with ethyl 4-chloroacetoace-
tate, ethyl benzoylacetate (Table 1, entries 2, 3) to furnish
coumarins (2a, 3a), respectively.
Encouraged by the above results, other phenolic sub-
strates were subjected to the Pechmann reaction using
7-Hydroxy-4-methyl-2H-chromen-2-one 1a Color-
1
less prisms, mp 183-185 °C; Yield 92%. H-NMR (400
Y(NO
3
)
3
×6H
2
O. In all cases, the reactions proceeded suc-
MHz, DMSO-d
(s, 1H), 6.470 (s, 1H), 5.957 (s, 1H), 2.292 (s, 3H). C-
NMR (100 MHz, DMSO-d ): d 160.09, 156.05, 155.96,
155.51, 143.93, 139.75, 128.34, 127.92, 127.75, 113.88,
6
): d 10.138 (s, 1H), 7.373 (m, 5H), 6.722
1
3
cessfully to afford the corresponding coumarins in good to
excellent yields. The electron-donating substituents in the
meta position to the phenolic –OH facilitated the cycliza-
tion. The reactivity of phloroglucinol (1,3,5-trihydroxy-
benzene) (entry 7) with ethyl acetoacetate was observed to
be higher than pyrrogallol (entry 14) due to two hydroxyl
groups at meta-positions in phloroglucinol compared to
one hydroxy group in pyrrogallol. Presence of meta-hy-
droxy group strongly activates the substrates due to reso-
nance effect. m-Methoxyphenol (entry 10) showed no de-
tectable demethylation under the reaction conditions. Simi-
larly, 1-naphthol (entry 12) requires a slightly higher tem-
perature and longer reaction time. These results were indi-
cated that addition to Influence of the catalyst acidity, reac-
tivity of phenolic substrates is also very important. Finally,
the reactions are remarkably clean, and no chromato-
graphic separation is necessary to get the spectra-pure com-
pounds.
6
-
1
112.52, 108.19, 105.44, 21.65. IR (KBr, cm ): (3000-
3400), 3050, 2900, 1690, 1615, 1590, 1500, 1080.
In conclusion, the present procedure of the synthesis
of coumarins by the Yttrium (III) nitrate hexahydrate cata-
lyzed condensation of phenol and b-ketoesters provides an
efficient and much improved modification of the von
Pechmann reaction. In addition to its simplicity and mild
reaction conditions, this method has the ability to tolerate a
wide variety of substitutions in both components. Thus,
this method will offer easy access to substituted coumarins
with varied substitution patterns in high yields. We believe,
our procedure will find important applications in the
synthesis of coumarins.
ACKNOWLEDGEMENTS
We acknowledge the research council of Yasouj Uni-
versity.
The suggested mechanism for the Pechmann conden-
sation of phenols with b-ketoesters in the presence of
Y(NO
3
)
3
×6H
2
O catalyst (Scheme II) has been described us-
×6H
REFERENCES
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3
)
3
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1
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