Calone

Calone is a synthetic benzodioxepinone used as a marine odorant. Its formula is CH₃C₆H₃(OCH₂)₂CO, and it is a derivative of 4-methylcatechol. The preferred IUPAC name is 7-methyl-2,4-dihydro-3H-1,5-benzodioxepin-3-one. It is a crystalline solid that is insoluble in water. It dissolves well in ethanol, dipropylene glycol and other organic solvents.

In 2014, Plummer et al. reported the synthesis and fragrance properties of several related aliphatic analogues. The isopropyl homologue of Calone was later released under the brand name Cascalone. Cascalone is a sweet, watery version of calone with a transparent floral signature.

Chemical identity

PubChem records Calone as 7-methyl-1,5-benzodioxepin-3-one under the title methyl benzodioxepinone. The original patent names the compound 7-methyl-3,4-dihydro-2H-1,5-benzodioxepin-3-one and calls ketones of this kind watermelon ketones.

Place among marine odorants

To find out how far the marine odor depends on the benzene ring, researchers built analogues carrying different substituents on it. These substituents gave a wide range of odor character. The patent methods were hard to apply to analogues with electron-withdrawing substituents, so a different route was used. An epoxide of epichlorohydrin was opened to give a protected dihalo alkylating agent, which allowed ether formation and ring closure, and removal of the protecting group followed by oxidation of the alcohols gave the ketones.

Preparation in the original patent

In the first example of the patent, the first step gives a mixture of 7- and 8-methyl esters, recovered in 95% crude yield. Heating this mixture in ethanol and hydrochloric acid and then distilling gives the 7-methyl ketone in 93% yield.

Later analogues

A European patent with a 1997 priority date describes 7-propyl-benzodioxepin-3-one for use in perfumery. A patent with a 2010 priority date covers benzodioxole derivatives as watery odorants.

Flavour use

In the patent, adding the ketones to unflavored gelatin and boiling water gives a gelled food with a pleasant watermelon taste and odor.