A Green Synthesis of Tetrahydrobenzo[b]pyran Derivatives
131
Experimental
References
Melting points were measured on an Electrothemal X6 mi-
croscopy digital melting point apparatus. IR spectra were
recorded on a Bruker Equinox-55 spectrometer using KBr
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General Experimental Procedure: Methods A and B
A solution of an aromatic aldehyde 1 (3mmol), 198mg ma-
lononitrile (2, 3 mmol), 420 mg dimedone (3, 3 mmol) and
N-methylimidazole (one drop, ca. 20mol%) in 10cm3 95%
EtOH (Method A) or in 10 cm3 H2O (Method B) was vigor-
ously stirred at room temperature for the specific time indicat-
ed in Table 1. The end of the reaction was monitored by TLC.
Then, the mixture was poured into water (Method A) or was
cooled in a refrigerator overnight (Method B) to precipitate
the solid. The crude product obtained was filtered off by suc-
tion and washed with 3ꢂ10 cm3 H2O. The pure product was
obtained by recrystallization from ethanol.
General Experimental Procedure: Method C
A mixture of as given above for Methods A and B was ground
for the appropriate time using a mortar and pestle of appropri-
ate size. The initial syrupy reaction mixture solidified within
4–30 min. The solid was washed with cold water and recrys-
tallized from ethanol.
All of the products are known and the data were found to be
identical with those reported in literature.
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Acknowledgements
We are grateful to the National Natural Science Foundation of
China (No. 20672046) and the Guangdong Natural Science
Foundation (No. 04010458).