Coffee furanone

Coffee furanone (2-methyltetrahydrofuran-3-one) is a pleasant smelling liquid furan derivative which is a volatile constituent of the aroma complex of roasted coffee.^[1] Coffee furanone is less odorous than furfuryl mercaptan, which with an odor threshold of 0.005 ppb was the first high impact aroma chemical, but has a very pleasant sweet caramel character, with some nuttiness.^[2]

Coffee furanone

Names
Preferred IUPAC name 2-Methyloxolan-3-one
Other names 2-Methyltetrahydrofuran-3-one; 2-Methyl-3-oxotetrahydrofuran; 2-Methyltetrahydro-3-furanone; Dihydro-2-methyl-3-furanone; 2-Methyldihydrofuran-3(2H)-one
Identifiers
CAS Number	3188-00-9 Y
3D model (JSmol)	Interactive image
ChemSpider	17494
ECHA InfoCard	100.019.715
PubChem CID	18522
UNII	I3703CL967 Y
CompTox Dashboard (EPA)	DTXSID9047677
InChI InChI=1S/C5H8O2/c1-4-5(6)2-3-7-4/h4H,2-3H2,1H3 Key: FCWYQRVIQDNGBI-UHFFFAOYSA-N InChI=1/C5H8O2/c1-4-5(6)2-3-7-4/h4H,2-3H2,1H3 Key: FCWYQRVIQDNGBI-UHFFFAOYAD
SMILES O=C1C(OCC1)C
Properties
Chemical formula	C5H8O2
Molar mass	100.117 g·mol−1
Density	1.040 g/cm3 (20 °C)
Boiling point	139 °C (282 °F; 412 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Synthesis

Coffee furanone was synthesized in 1963 by Wynberg via acid-catalyzed ring closure of β-alkoxy diazoketones.^[3] Coffee furanone has also been prepared via the condensation of ethyl lactate and methyl acrylate in DMSO solution^[4] and (under phase transfer conditions) in ionic liquids.^[5] A related lactic acid synthesis was described as having the advantages of a simple process, high conversion rate, low pollution, and low cost.^[6] This compound has also been prepared in acceptable yield via oxidative hydroxylation of the 2-acetylbutyrolactone.^[7] Further approaches to the synthesis of coffee furanone involved the hydrolysis of the corresponding dithioketals^[8] and the oxidation of 2-methyltetrahydrofuran employing lithium hypochlorite in the presence of ruthenium catalysts.^[9]

Applications

The synthetic version of this natural flavorant and odorant is used in a variety of food and beverage applications, including coffee, nuts, cocoa, brandy, meat sauces and as a general food flavorant at a typical dosage (about 5-20 ppm), similar to the natural concentration (30 ppm) of coffee furanone in roasted coffee.^[10][11]