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Amulrao Borse 1 and Mahesh Patil 1 and Nilesh Patil 1 and Rohan Shinde 2
Recommended by J. Drabowicz and H. A. Jimenez-Vazquez and F. Machetti and F. C. Pigge and H. Wakamatsu
1, School of Chemical Sciences, North Maharashtra University, Jalgaon 425 001, India
2, Department of Pharmacology, R. C. Patel Institute of Pharmaceutical Education & Research, Shirpur 425 405, India
Received 4 April 2012; Accepted 25 June 2012
This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
1. Introduction
The widespread interest in 3,4-dihydropyrimidin-2(1H)-ones, Biginelli compounds, has resulted in enormous efforts towards the synthesis of this biologically important moiety. Several methods have been developed for the synthesis of these compounds, but most of these protocols involve expensive reagents, strong acid catalysts, solvents, of prolonged reaction time and even then provide the products in unsatisfactory yields. With the current global awareness of developing environmentally friendly technologies, it is a need to perform a reaction in neat and nonhazardous conditions for providing a green approach towards organic synthesis [1]. Therefore, it was decided to develop an efficient method for the synthesis of Biginelli compounds. In this communication, we report a straightforward and simple procedures for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones using a mixture of phosphorus pentoxide-methanesulfonic acid (Eaton's reagent).
Eaton's reagent (1 : 10 phosphorus pentoxide in methanesulfonic acid) is an inexpensive and commercially available substance synthesized by Eaton in 1973 and found to be a good alternative to polyphosphoric acid which enables the drawbacks of many traditional catalysts to be overcome, because it has a much lower viscosity, it is easier to handle, and no complex separation procedures need to be employed [2]. Many processes that employ a mixture of P 2 O5 /MeSO3 H are not only more economical, but also they are more environmentally friendly and offer a number of distinct advantages such as safe in industrial scale, no additional solvent required, chlorine-free, rapid reactions, and high-purity products with excellent yields. The distinctive physical and chemical properties of Eaton's reagent make it a very useful substance in many different reactions with different applications. The mixture of P 2 O5