Rosefuran (3-methyl-2-prenylfuran) is a liquid boiling at 103-104 °C (at 50 mm Hg), with a density of 0.9089 g/cm3 (at 30 °C), less than that of water. It is an aroma chemical which is a minor constituent of the aroma of the rose (Rosa damascene). Rosefuran is a 2,3-disubstituted furan (3-methyl-2-(3-methyl-2-buten-1-yl)furan). It has an odor threshold of 200 ppb and constitutes 0.16% of Bulgarian rose oil. Rosefuran has been established as a female sex pheromone of an acarid mite, Caloglyphus sp. Concentrations of less than 100 ng of synthetic rosefuran caused sexual excitation in males of the species.
Synthesis
Rosefuran was synthesized in 1968 by
George Büchi via the organomercury compound bis(3-methyl-2-furyl)mercury. Rosefuran has been synthesized in many steps from common starting materials starting with prenyl chloride (3-methyl-but-2-en-1-yl chloride). Rosefuran has also been synthesized via cyclization of suitable acyclic precursors, such as, 5-oxogeraniol and 5-hydroxycitral (4-hydoxy-3,7-dimethyl-(E)-2,6-octadienol). Rosefuran has also been prepared via palladium catalyzed cross coupling of the methyl ester of 4-bromo-5-methyl-2-furancarboxylic acid followed by decarboxylation.
Alternatively, rosefuran has been prepared from other furan derivatives. Thus,
Wittig reaction
The Wittig reaction or Wittig olefination is a chemical reaction of an aldehyde or ketone with a triphenyl phosphonium ylide called a Wittig reagent. Wittig reactions are most commonly used to convert aldehydes and ketones to alkenes. Mos ...
of 3-methyl-2-furanacetaldehyde with triphenylphosphonium isopropylide gave rosefuran in 67% yield. The aldehyde was obtained via
Claisen rearrangement
The Claisen rearrangement is a powerful carbon–carbon bond-forming chemical reaction discovered by Rainer Ludwig Claisen. The heating of an allyl vinyl ether will initiate a ,3sigmatropic rearrangement to give a γ,δ-unsaturated carbonyl, ...
of 3-(vinyloxymethyl)furan. Similarly, the readily available
3-bromofuran was reacted with 3,3-dimethylallyl bromide and
lithium diisopropylamide
Lithium diisopropylamide (commonly abbreviated LDA) is a chemical compound with the molecular formula . It is used as a strong base and has been widely utilized due to its good solubility in non-polar organic solvents and non-nucleophilic nature ...
in THF solution, followed by reaction at with methyl iodide and
N-butyllithium
''n''-Butyllithium C4H9Li (abbreviated ''n''-BuLi) is an organolithium reagent. It is widely used as a polymerization initiator in the production of elastomers such as polybutadiene or styrene-butadiene-styrene (SBS). Also, it is broadly emp ...
in THF, yielding rosefuran.
A patented process for the manufacture of rosefuran via condensation of 3-formylpropionic acid methyl ester with
crotonaldehyde
Crotonaldehyde is a chemical compound with the formula CH3CH=CHCHO. The compound is usually sold as a mixture of the ''E''- and ''Z''-isomers, which differ with respect to the relative position of the methyl and formyl groups. The ''E''-isomer ...
has been described. The intermediate ketoaldehyde is cyclized to a furan derivative which is converted to rosefuran in 33% overall yield via
Grignard reaction
The Grignard reaction () is an organometallic chemical reaction in which alkyl, allyl, vinyl, or aryl-magnesium halides (Grignard reagent) is added to a carbonyl group in an aldehyde or ketone. This reaction is important for the formation of ...
to give 2-methyl-4-(3-methyl-2-furanyl)-2-butanol followed by dehydration.
Applications
Rosefuran is a desirable component of rose oil, a natural fragrance material. Rosefuran is the major constituent (58% by weight) of the essential oil of ''
Perilla
''Perilla'' is a genus consisting of one major Asiatic crop species ''Perilla frutescens'' and a few wild species in nature belonging to the mint family, Lamiaceae. The genus encompasses several distinct varieties of Asian herb, seed, and veget ...
ocimoides'', a herbaceous, annual plant cultivated in
Bangladesh
Bangladesh (}, ), officially the People's Republic of Bangladesh, is a country in South Asia. It is the eighth-most populous country in the world, with a population exceeding 165 million people in an area of . Bangladesh is among the mos ...
and used as a component of a common spice. Additionally, synthetic rosefuran is recommended (average recommended level in parentheses) for use as a flavor, fragrance chemical for a wide variety of applications including baked goods (5 ppm), breakfast cereal (2 ppm), cheese (3 ppm), condiments (2 ppm), frozen dairy (3 ppm), soups (2 ppm) and snack foods (5 ppm).
[rosefuran: http://www.thegoodscentscompany.com/data/rw1435551.html]
References
{{DEFAULTSORT:Rosefuran
Furans