Safarzaei, "Potassium sodium tartrate as a versatile and efficient catalyst for the one-pot synthesis of pyran
annulated heterocyclic compounds in aqueous media," Research on Chemical Intermediates.
Bis-spiropyrans contain two photochromic spiropyran units in the molecule and achievable opening of two pyran cycles allow one to suggest such compounds as a prototypes for the multistate light-driven molecular switches  that can be controllably and reversibly switched between three or more well-distinguished states.
For instance, there were not any examples of observed and well-proved scission of two carbon-oxygen bond in a single bis-spiropyran molecule until quite recently, when we had shown that nonsymmetric bis-spiropyran Figure 2 (1) containing not only indoline but also benzoxazine moiety could undergo opening of two pyran cycles .
Nawwar, "Salicylamides containing amino acid or pyran moieties with molluscicidal activity," Archiv der Pharmazie, vol.
Keshipoor, "Ti[O.sub.2] and Ti[O.sub.2] nanoparticles as efficient and recoverable catalysts for the synthesis of pyran annulated heterocyclic systems," Research on Chemical Intermediates, 2012.
Moreover heterocyclic compounds containing pyran
ring also present a wide properties of biological activities such as anticancer, spasmolytic, diuretic, anticoagulant [15, 16].