Benzopyran

As chromenes (also: Benzopyrans ) the two organic chemical compounds 2H- chromene and 4H- chromene be called. These are among the aromatic compounds and the heterocyclic compounds, as the hetero atom of oxygen is contained in the ring system. Both substances are isomers that differ only in the position of the double bond in the heterocyclic six-membered ring.

Deposits, derivatives and use

2H- chromene occurs in the Myrtle family Calyptranthes tricona. Derivatives of 2H- chromene act as potent potassium channel openers and are used as drugs ( cromakalim, Lemakalim ); Carbocromene is used for cardiac therapy. From 2H- chromene to coumarin and umbelliferone derive from 4H- chromen the chromone, anthocyanidins and flavones. By hydrogenation of the pyran ring to obtain the chroman, which is the basic building block of the tocopherols, and the rotenoids some cannabinoids, for example. Many alkaloids containing a chromene scaffold as a chromophore.

Isochromene

Chromenes of the two positional isomers are the 1H - and 3H- isochromene isochromene, in which the oxygen atom is in position 2.

3H- isochromene

Representation

A simple one-step synthesis of 2H - chromene by Yoshiyuki Kawase is possible by direct cyclization of salicylaldehyde with Propencarbonsäureestern in DMF. The synthesis of 2H- chromene is also achieved by a Wittig reaction and subsequent cyclisation, starting from the sodium salt of salicylaldehyde and Vinyltriphenylphosphoniumbromid.