Tetrahedron Letters
4
viable green methodology for solvent- and catalyst-free 14. (a) Kaan, H. Y. K.; Ulaganathan, V.; Rath, O.;
reactions. Further research to widen the scope of this
enhanced protocol is in progress.
Prokopcova, H.; Dallinger, D.; Kappe, C. O.; Kozielski,
F. J. Med. Chem. 2010, 53, 5676. (b) Kappe, C. O. Eur.
J. Med. Chem. 2000, 35, 1043. (c) Butters, M.; Davies,
C. D.; Elliott, M. C. Org. Biomol. Chem. 2009, 7, 5001–
5009.
Acknowledgements:
We express special gratitude to the Director, DRDE,
Gwalior, for his keen interest and encouragement.
15. Suresh, Sandhu, J. S., ARKIVOC, 2012, 66-133.
16. Typical experimental procedure (transesterification
transfomation): A homogeneous mixture of an alcohol
(1.5 equiv.) and methylacetoacetate (1.0 equiv.) was
charged in a round bottomed flask and gently heated at
110 ˚C under solvent-free, catalyst-free conditions, for a
certain period of time as required. The progress of the
reaction was monitored by TLC. After completion, the
resulting desired product was distilled out directly or
separated by short column chromatography over silica
gel using light petroleum ether and ethylacetate (80:20)
to afford the pure product in 60-92% yield.
17. Typical Experimental Procedure (Biginelli reaction): A
25ml round bottom flask equipped with a reflux
condenser was charged with arylaldehyde (1.0 equiv.)
and urea (1.2 equiv.). Both precursors were finely
powdered and mixed together and allowed to stir for 30
min at room temperature. The β-ketoester (1.0 equiv.)
was subsequently added to above mixture. The resulting
reaction mixture was heated at 110 ˚C (oil bath) under
solvent- and catalyst-free conditions with constant
mechanical stirring for 3h. The progress of the reaction
was monitored by TLC (6 : 4, hexane : ethylacetate ).
After completion of the reaction as indicated on TLC, the
contents were cooled to room temperature and the crude
reaction mixture was crushed and washed with chilled
water (15ml x 3), filtered and dried under vacuum. For
analytically pure products, the final solid mass was
washed with diethyl ether (10ml x 2) to remove the un-
reacted reagents to afford the pure product in 82-92%
yield.
Supplementary data:
Supplementary data (Details experimental procedure and
characterization data of selected compounds and copies of
1H NMR and 13C NMR spectras are given in supplementary
material) associated with this article can be found.
References and note:
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