Abstract:
A large variety of natural products of biological importance contain xanthenes and
bcnzoxanthenes as an integral part of their structures. Xanthenes are of great interest in organic
synthesis owing to their various biological activities, their application in photodynamic therapy
and their use as dyes and fluorescent materials for visualizing biomolecules. The arenofurans
are well known for their antibacterial, antiviral, anticancer, mutagenic, antifertility activities.
They act as inhibitors of hepatocyte nuclear factor 4-alpha, agonist for nicotinic
acetylcholine receptor and inhibitor of nuclear transcription factor kappa-3.
Keeping the importance of these heterocycles in mind, we have developed a methodology for
the synthesis of these compounds using simple, mild, efficient and cost effective catalysts. The
cheap, easily available and easily removable silica sulphuric acid has been used as catalyst for
the solvent-free synthesis of dibenzoxanthesnes. The reaction procedure is quite simple, rapid
and dibenzoxanthenes are formed exclusively in good yields. We have demonstrated basic
alumina as a novel promoter for the coupling of f3-naphthols and 3-nitrostyrenes to afford
naphthofurans in good to high yields under solvent-free conditions. The simplicity of
experimental procedure and ready availability of catalyst and starting materials render this an
experimentally attractive method for the synthesis of naphthofurans. The reaction of anaphthol
with -nitrostyrenes is less effective and produced the corresponding naphthofurans
in low yields. This may be attributed for the less reactivity of f3-position of a-naphthol in
comparision to that of a-position of I3-naphthol. All the compounds were fully characterized by
analytical tools and by comparison of the known data for the available compounds.
