Background:
The various industrial processes have a diverse effect on the environment
through pollution. In view of these observations, some environmentally benign synthetically protocols
have developed under green chemistry. For rapid and sustainable synthesis, the microwave
irradiation (MI) has gained popularity as a powerful tool compared to conventional synthesis. The
present study describes the synthesis of novel substituted 1, 3-diaryl-2-propene-1-one derivative
using alumina supported K3PO4-MWI combination.
Objective:
Chalcones are important compounds which are widely spread in nature like in fruits,
vegetables, tea, spices, etc. The 2’-hydroxy derivative of chalcones plays an important role in the
synthesis of bioactive compounds. The present communication deals with a convenient and rapid
synthesis of 1, 3-diaryl-2-propene-1-one under the support of alumina-tripotassium phosphate and microwave
irradiation. Our efforts are focused on the introduction of typical and easier route for the
synthesis of title compounds using a microwave. All synthesized chalcones have been screened and
evaluated for the antioxidant activity by DPPH and nitric oxide radical scavenging. Some of these compounds
are found to be more potent scavengers and may lead to the development of a new class of antioxidants.
Methods:
The α, β-unsaturated carbonyl functionality contains two electrophilic centers allowing
them to undergo addition and cyclization reactions with different nucleophiles. In the literature
survey, we found that Chalcones were synthesized using tripotassium phosphate catalyst under refluxing
by a conventional method. A novel method for the synthesis of 1, 3-diaryl-2-propene-1-one
via Claisen Schmidt has been introduced by reacting substituted 2’- hydroxyl acetonaphthones with
substituted aromatic aldehydes under the support of basic alumina –tripotassium phosphate via microwave
radiations. Formation of corresponding Chalcones was confirmed by spectral studies followed
by their screening for antioxidant activity. The scavenging activity is expressed in terms of
% inhibition and IC50 value (μg/ml).
Results:
The structures of newly synthesized Chalcones were confirmed and in good agreement
with obtained spectral analysis such as IR, NMR, Mass and elemental analysis. Commercially
available basic alumina and tripotassium phosphate in combination of microwave were utilized
and found to be effective, convenient route for the synthesis of 1, 3-diaryl-2-propene-1-one derivatives
with desirable yields in short reaction time (5-12 min). The results of antioxidant activity
revealed that the IC50 value for compounds 3a, 3d, 3e, 3f, 3g, 3h, 3j, 3l and 3n are lower than
that of standard ascorbic acid to scavenge DPPH radical. This indicates that these compounds are
more significant scavengers in comparison with standard drug. On the other hand, compounds 3a,
3b, 3c, 3d, 3g, 3l and 3n are more potent scavengers for NO free radical.
Conclusion:
We have introduced an efficient, ecofriendly, simple and fast microwave assisted
method using basic alumina-tripotassium phosphate for the synthesis of 1, 3-diaryl-2-propene-1-
one derivatives. Microwave irradiation provides an effective way for the preparation of Chalcones
in terms of several advantages as a simple procedure, short reaction time, milder reaction condition,
cleaner reaction and excellent yield. The scavenging activity of chalcones against DPPH and NO free
radicals showed excellent properties of antioxidants.
Substrate Directed Regioselective Monobromination of Aralkyl Ketones Using N-Bromosuccinimide Catalysed by Active Aluminium Oxide: α-Bromination versus Ring Bromination