Background: Over a decade, a number of papers have been published on the usage of ionic
liquids (ILs) and Microwave-Assisted Organic Synthesis (MAOS), which displayed their benefits with
respect to the conventional synthetic procedures, for current generation of fast, efficient and environmental
friendly synthetic methodologies. The aim of the present study is the synthesis of linear and angular
spirochromanone derivatives using microwave irradiation with the IL. As the microwave assisted
organic synthesis (MAOS) with IL as a solvent is environmental friendly and non-volatile, therefore it
allows simple separation and catalyst recycling.
Methods: Though various methods for the synthesis of linear and angular spirochromone derivatives
have been developed, one of the widely used methods is the Kabbe condensation synthesis. In this paper,
we report an efficient synthesis of spirochromone conjugates by substituted 1-(6-hydroxy-3-
methylbenzofuran-5-yl) ethan-1-one (1a) linear isomer or 1-(4-hydroxy-3-methylbenzofuran-5-
yl)ethan-1-one (1b) angular isomer with various cycloalkanones catalyzed by pyrrolidine in ionic liquid
[bmim]Cl.AlCl3 under microwave irradiation.
Results: The comparative results of 3a-g (linear isomers) and 4a-g (angular isomers) are summarized in
Table 1. A series of new spirochromone conjugates synthesized were purified by column chromatography
and obtained with good yields. All new compounds were synthesized and characterized by 1H
NMR, 13C NMR, IR and LCMS.
Conclusion: A new series of linear/angular spirochromanone derivatives (3a-g/4a-g) have been successfully
synthesized under conventional and microwave irradiation methods using ionic liquid as solvent.
The microwave irradiation with the ionic liquid mediated method has proven to be highly yielding
with a higher rate of acceleration and being eco-friendly.