l-proline as an efficient asymmetric induction catalyst in the synthesis of chromeno[2,3-d]pyrimidine-triones, xanthenes in water

The multi-component reactions involving aromatic aldehydes, dimethylcyclohexane-1, 3-dione/cyclohexane-1, 3-dione and barbituric acids were carried out in presence of the organo catalyst l-proline in aqueous medium at ambient temperature. The reactions afforded chromeno[2,3-d]pyrimidinones in excellent yields and with high enantioselectivities. The above reactions exhibited the efficient asymmetric induction property of the organo catalyst l-proline as reported earlier. In the absence of barbituric acid the method proved equally efficient when aromatic aldehydes readily condensed with 2 mol of cyclohexane-1, 3-dione in presence of l-proline to give Xanthenes derivatives in good yields. The protocol reported here is benign to the environment as water is used as the solvent and purification does not involve any chromatographic procedures. Selected compounds were further studied using DFT calculations in order to establish a clear picture about the geometric parameters and the electronic absorption spectra of the compounds.

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