Titanium aminophosphates as efficient,economical, and recyclable catalysts for the synthesis of xanthenediones

Titanium aminophospates have been used as catalysts in the synthesis of xanthenediones at room temperature. Among the three catalysts tested, titanium n-propyl aminophosphate (TNPAP) was found to be more efficient catalyst for the synthesis of xanthenediones. The solvent-screening studies for this catalytic reaction reveals that MeOH: H₂O was the most suitable solvent system, yielding higher amounts (89%) of products. The TNPAP catalyst was found to be reusable for five successive cycles. The optimized reaction conditions are 1.0?mmol of benzaldehyde, 2.0?mmol of dimedone, methanol/water (5.0?mL) as solvent, rt, and 100?mg of TNPAP. A plausible mechanism for the catalytic reactions has been proposed.