Categories: Synthesis of O-Heterocycles >
Synthesis of Coumarins
Name Reactions
Recent Literature
The employment of hydrophobic ionic liquids
dramatically enhanced the activity of metal triflates in Friedel-Crafts
alkenylations of aromatic compounds with various alkyl- and aryl-substituted
alkynes.
C. E. Song, D.-U. Jung, S. Y. Choung, E. J. Roh, S.-G. Lee, Angew. Chem., 2004, 116,
6309-6311.
The basic ionic liquid 1-butyl-3-methylimidazolium hydroxide, [bmIm]OH,
efficiently catalyzes the Knoevenagel condensation of various aliphatic and
aromatic aldehydes and
ketones with active methylenes at room temperature without requirement of any
organic solvent.
B. C. Ranu, R. Jana, Eur. J. Org. Chem., 2006, 3767-3770.
A facile, convenient, efficient, and high yielding synthesis of a
combinatorial library of 3-aroylcoumarins has been developed by the
condensation of easily available -aroylketene dithioacetals and
2-hydroxybenzaldehydes in the presence of catalytic amount of piperidine in
THF reflux.
H. S. P. Rao, S. Sivakumar, J. Org. Chem., 2006, 71, 8715-8723.
The ionic liquid 1-butyl-3-methylimidazonium tetrafluoroborate [bmim]BF4
was used for ethylenediammonium diacetate (EDDA)-catalyzed Knoevenagel
condensation between aldehydes or ketones with active methylene compounds.
Catalyst and solvent can be recycled.
C. Su, Z.-C. Chen, Q.-G. Zhen, Synthesis, 2003, 555-559.
A new carbamoyl Baker-Venkataraman rearrangement allows a general synthesis of
substituted 4-hydroxycoumarins in good overall yields. Intermediate arylketones
are efficiently prepared via a Directed ortho Metalation - Negishi cross
coupling protocol from arylcarbamates. The overall sequence provides a
regiospecific anionic Friedel-Crafts complement for the construction of ortho-acyl
phenols and coumarins.
A. V. Kalinin, A. J. M. Da Silva, C. C. Lopes, R. S. C. Lopes, V. Snieckus,
Tetrahedron. Lett., 1998, 39, 4995-4998.
