La2O3 as a very effective double-functional catalyst for the production of 2-amino-4-aryl-4H-pyrans and Pyrazolopyranopyrimidines

Lanthanum (III) oxide (La2O3) was applied as an efficient bifunctional catalyst to develop a new methodology in the production of 2-amino-4-aryl-4H-pyrans and pyrazolopyranopyrimidines in the absence of solvent. In both synthetic protocol, due to the dual functionality of lanthanum (III) oxide (i.e. having basic and acidic Lewis sites), it was very useful and general, and plausible mechanisms were presented in support of this generality and high capability. The current protocol featured environmentally friendly conditions, the ability to recycle and reuse the heterogeneous catalyst up to 6 times, providing products in short times with high yields, easy work-up and no need for difficult steps of catalyst synthesis by using a commercially available catalyst, which makes it an appealing route for the preparation of these derivatives.