Abstract
Polyethylene glycol (PEG) was found to be an inexpensive nontoxic
and effective medium for the one-pot synthesis of N-substituted
azepines under catalyst-free conditions in excellent yields. Environmental
acceptability, low cost, high yields, and recyclability of the PEG
are the important features of this protocol.
Key words
anilines - dialkylacetylene dicarboxylates - 2,5-dimethoxytetrahydrofuran - N-substituted
azepines - polyethylene glycol - catalyst-free
conditions
References and Notes
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General Procedure
for the Synthesis of N-Substituted Azapins by Using PEG as a Reaction
Medium
A mixture of the requisite aniline (1.0 mmol),
dialkyl-acetylene dicarboxylate (1.0 mmol), and 2,5-dimethoxy-tetrahydrofuran
(1.0 mmol) was taken in PEG (5 mL) and stirred at 60 ˚C
for the appropriate time. After completion of the reaction, as monitored
by TLC, the reaction mixture was poured into H2 O and
extracted with EtOAc. The organic layer was removed under reduced
pressure, and the crude product was purified by column chromatography.
The recovered PEG could be reused for a number of cycles without
significant loss of activity.