Nano perlite sulfuric acid: an inexpensive heterogeneous acid catalyst for the synthesis of 1,8-dioxo-octahydroxanthenes and tetrahydrobenzoxanthenes under solvent-free conditions

Nano perlite sulfuric acid (n-PeSA) as an inexpensive powerful solid acid nanocatalyst has been successfully applied for the efficient and green synthesis of 1,8-dioxo-octahydroxanthenes and tetrahydrobenzoxanthenes under solvent free condition in excellent yield. These new procedures offer many advantages including ease of preparation and handling, low cost and low toxicity of catalyst, environmental friendliness reaction conditions, short reaction time and absence of any tedious workup or purification .Furthermore, the catalyst could be recycled and reused at least five times without appreciable deterioration in catalytic activity, confirming the stability of the covalent bonding of acidic centers.