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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



heterocyclic compounds that contain an oxygen atom and two conjugated (α-pyrene) or isolated (γ-pyran) double bonds. Pyrans are highly unstable compounds: α-pyran is only known in derivative form, and γ-pyran is a colorless liquid with a boiling point of 84°C (with decomposition; also decomposes rapidly at room temperature).

Dihydropyrans and tetrahydropyrans are most stable and more readily accessible. Important pyran derivatives are αpyrone

and γ-pyrone. The pyran ring is a structural feature of many natural substances. For example, most hexoses (aldoses and ketoses) are essentially six-membered pyranoses.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
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 [7] 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 [9].
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].