Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1996-11-06
1999-06-01
Kight, John
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
549418, C07D31500
Patent
active
059089415
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a process for producing certain gamma pyrones such as maltol and ethyl maltol, which process is characterized by the use of a dry aprotic solvent as a reaction medium.
BACKGROUND OF THE INVENTION
Maltol is a naturally occurring substance found in the bark of young larch trees, pine needles and chicory. Maltol has the structure ##STR1## Maltol is one of a family of compounds called gamma pyrones which enhance the flavor and aroma of a variety of food products and which, in general, have the formula ##STR2## wherein R is hydrogen, (C.sub.1 -C.sub.6)alkyl, (C.sub.2 -C.sub.6)alkenyl, phenyl, or benzyl. The compounds wherein R is methyl (maltol) or ethyl (ethyl maltol) are regulated for use as flavor enhancers in foods. In addition, these materials are used as ingredients in perfumes and essences. Pyromeconic acid (formula II, R.dbd.H) derivatives such as the 2-alkenylpyromeconic acids reported in U.S. Pat. No. 3,365,469 inhibit the growth of bacteria and fungi and are useful as flavor and aroma enhancers in foods and beverages and aroma enhancers in perfumes.
Many processes for producing maltol have been reported. Early commercial production was from the destructive distillation of wood. Synthesis of maltol from 3-hydroxy-2-(1-piperidylmethyl)-1,4-pyrone was reported by Spielman and Freifelder in J. Am. Chem. Soc., 69, 2908 (1947). Schenck and Spielman, J. Am. Chem. Soc., 67, 2276 (1945), obtained maltol by alkaline hydrolysis of streptomycin salts. Chawla and McGonigal, J. Org. Chem., 39, 3281 (1974) and Lichtenthaler and Heidel, Angew. Chem., 81, 998 (1969), reported the synthesis of maltol from protected carbohydrate derivatives. Shono and Matsumura, Tetrahedron Letters No. 17, 1363 (1976), described a five step synthesis of maltol starting with methyl furfuryl alcohol.
Syntheses of gamma-pyrones such as pyromeconic acid, maltol, ethyl maltol and other 2-substituted-3-hydroxy-gamma-pyrones are described in U.S. Pat. Nos. 3,130,204; 3,133,089; 3,140,239; 3,159,652; 3,365,469; 3,376,317; 3,468,915; 3,440,183; 3,446,629; 4,082,717; 4,147,705; 4,323,506; 4,342,697; 4,387,235; 4,390,709; 4,435,584; and 4,451,661. A typical process for making gamma pyrones is illustrated by U.S. Pat. No. 4,435,584 to Brennan et al. This patent describes a one pot, furfuryl alcohol based synthesis wherein all reactions are conducted in aqueous/protic media. The present invention is based on chemistry which can employ a furfuryl alcohol precursor, but which, by contrast, employs a reaction medium comprising an aprotic solvent to effect the conversion of a haloenone to the desired gamma pyrone product.
U.S. Pat. No. 4,126,624 discloses preparation of gamma-pyrones from 3-substituted furans by procedures which can employ isolation of various components by extraction with various organic solvents.
SUMMARY OF THE INVENTION
This invention, in one aspect, provides a method of synthesizing compounds having the formula ##STR3## wherein R is (C.sub.1 -C.sub.6)alkyl, (C.sub.2 -C.sub.6)alkenyl, phenyl, or benzyl, comprising treating, at a temperature above about 40.degree. C., preferably above about 60.degree. C., and in a reaction medium comprising an aprotic solvent, a compound (a haloenone) having the formula ##STR4## wherein R is as defined above, R.sup.1 is (C.sub.1 -C.sub.6)alkyl or hydroxy(C.sub.2 -C.sub.4)alkyl, and X is chloro or bromo, with a catalytically effective amount of acid, thereby effecting conversion of said compound III to said compound II. While temperatures as high as 200.degree. C. or higher can be employed, it is most preferred to conduct the reaction at a temperature within the range of about 80.degree. C. to about 120.degree. C.
The above discussion illustrates a reaction in which haloenone III is converted to gamma pyrone II. The acronym "H-T-GP" is herein employed as an abbreviation for the phrase "haloenone-to-gamma pyrone" for convenience.
A haloenone of formula III can be generated by reacting a corresponding furfuryl alcohol of formula IV, with a halogen
REFERENCES:
patent: 4126624 (1978-11-01), Brennan et al.
patent: 4342697 (1982-08-01), Weeks et al.
patent: 4390709 (1983-06-01), Weeks et al.
patent: 4435584 (1984-03-01), Brennan et al.
patent: 4451661 (1984-05-01), Weeks et al.
Weeks et a l., J. Org. Chem., 1980, 45, pp. 1109-1113.
Harada et al., Agric. Biol. Chem., 47(12), pp. 2921-2922, 1983.
Fung Fu-Ning
Hay Bruce A.
Swenarton, deceased James E.
Covington Raymond
Cultor Ltd.
Kight John
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