B(C6F5)3 catalyzed Biginelli reaction
Acknowledgements
The authors thank Department of Pharmaceuticals,
Ministry of Chemicals and Fertilizers for providing
funds and also acknowledge Indian Institute of Chemi-
cal Technology, Hyderabad, for the scientific and instru-
mental support.
Scheme 2. B(C6F5)3 catalyzed 5 g scale synthesis of
monastrol.
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Scheme 3. Plausible mechanism for dihydropyrimidinones
synthesis using B(C6F5)3.
intramolecular cyclo-addition and concomitant loss of
water to afford dihydropyrimidinone (4a) (scheme 3).
4. Conclusions
We have demonstrated an extremely facile and efficient
protocol for the synthesis of 3,4-dihydropyrimidin-
2-(1H) ones and their thione analogues via one-
pot cyclocondensation of aldehydes, urea/thiourea
and β-ketoester/β-diketone using catalytic amount of
B(C6F5)3. The resulting protocol was proved to be
suitable for a wide range of substrates. Furthermore,
the present methodology was effectively extended to
the large-scale synthesis of monastrol, which signifies
its suitability for industrial application. Moreover, this
method offers several advantages including mild reac-
tion conditions, eco-friendliness, low catalyst loading,
low toxicity, short reaction time, high yields and purity.
Another important aspect of this procedure is tolerance
of acid-sensitive protecting groups such as TBDMS and
TBDPS and compatibility with a variety of functional
groups under the present reaction conditions.
Supplementary Information
Spectral data for the synthesized compounds can be