Trisodium citrate, a natural non-toxic compound, is used as a catalyst for an efficient, rapid,
one-pot synthesis of tetrahydrobenzo[b]pyrans and dihydropyrano[c]chromenes in moderate
to excellent yields and under eco-friendly conditions. The catalyst is environmental benign,
easy handling, non-toxic, stable in air, inexpensive and could be reused at least five cycles
without losing its activities.