Oxygen-containing aliphatic compounds and their use as intermedi

Details Oxygen-containing aliphatic compounds and their use as intermedi Oxygen-containing aliphatic compounds and their use as intermedi

1995-04-13

1996-12-03

Reamer, James H.

Organic compounds -- part of the class 532-570 series

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

568385, 568405, 568413, 568673, C07D30314

Patent

active

055809960

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD AND PRIOR ART

This appln is a 371 of PCT/IB94/00261, Sep. 01,1994.
4-Hydroxy-2,5-dimethyl-3(2H)-furanone, a compound better known under its commercial tradename of Furaneol.RTM. [registered trademark of Firmenich SA, Geneva], is an essential component of the pineapple and strawberry aromas and, in this capacity, it is widely used in the flavor industry. As a result of its organoleptic properties, it has found extensive use in a wide number of flavoring compositions, wherein it enhances the fruity and caramel note characteristic of the above-mentioned fruits.
Since its discovery, there have been suggested quite a number of methods for its preparation, amongst which it is fitting to cite the synthesis which resorts to the use of hex-3-yne-2,5-diol as a starting product [see Swiss patent no 474'500]. This process can be thus represented: ##STR2##
Although this type of process is quite satisfactory from an industrial point of view, it is nevertheless defined by critical steps which require specific industrial facilities and meticulous handling. Thus, it is not surprising to observe that many research teams have been looking into this problem. However, no valid alternative has been able to impose itself up until now.


DESCRIPTION OF THE INVENTION

The present invention is intended to bring a novel solution. More particularly, it relates to oxygen-containing aliphatic compounds which can be used as intermediate products for the preparation of Furaneol.RTM.. The compounds in question here are the di-tert-butyl and diisoamyl esters of hex-3-yne-2,5-diol, or 2,5-di-tert-butyloxy-hex-3-yne and 2,5-diisoamyloxy-hex-3-yne, as well as 2,5-di-tert-butyloxy-hexane-3,4-dione and 2,5-diiosamyloxy-hexane-3,4-dione. These are novel compounds which are obtained by an original process which is also the object of the present invention, which process is characterised in that values of zero or 1 and wherein n+m=2, to form an acetylenic ether of formula ##STR3## wherein index p represents an integer equal to 2 or 3 and q can be zero or 1 and wherein p+q=3; and ruthenium tetroxide, in the presence of an agent capable of re-oxidising the formed RuO.sub.2, to provide the corresponding hexane-3,4-dione of formula ##STR4## wherein indexes p and q have the meaning indicated above.
Hex-3-yne-2,5-diol, used as starting product in the process of the invention, is a commercially available product. As the ethylenic reagent of formula (I), there is used isobutene (n=2; m=0) or 2-methyl-but-2-ene (n=m=1). The latter can be replaced by isoamylene, a mixture containing predominant amounts of 2-methyl-but-2-ene together with its isomer 2-methyl-but-1-ene.
This first step of the process of the invention, which formally consists in the etherification of the hexyne-diol, is preferably carried out in anhydrous medium and at a temperature below 80.degree. C., and preferably comprised between 0.degree. and 40.degree. C. The reaction can be carried out continuously, or batchwise in an autoclave.
Since hex-3-yne-2,5-diol is viscous at low temperature, it is more convenient to operate in the presence of a solvent, which also allows better control of the reaction's exothermicity. To this end, ethers such as methyl-tertbutyl ether or diisopropyl ether are particularly convenient. Aromatic solvents such as toluene can also be used.
In this way, the 2,5-di-tert-butyloxy- or 2,5-diisoamyloxy-hex-3-yne obtained in organic solution can be directly employed in the following step of the process, without separation or subsequent purification.
The etherification reaction is also favored by the action of an anhydrous acidic catalyst. This can be a protonic acid, for example p-toluenesulfonic acid, a Lewis-type acid such as BF.sub.3.Et.sub.2, or yet an acid resin such as the sulfonic resins. The particular choice amongst these reagents will be made on the basis of economic considerations, availability of the reagent and protection of the environment. In this manner, we obtained particularly high, close to quantitative, yields.
The second step of the

REFERENCES:
patent: 3576014 (1971-04-01), Meyrin et al.
patent: 3728397 (1973-04-01), Re et al.
patent: 3853916 (1974-12-01), van den Ouweland
patent: 4290960 (1981-09-01), Ross et al.
patent: 4464409 (1984-08-01), de Rooij
Harsh Gopal et al. "Ruthenium Tetroxide Oxidation of Alkynes. A New One Step Synthesis of Alpha-Kiketones"; Tetrahedron Letters No. 31, Juillet 1971, Oxford GB, pp. 2941-2944.
Eugen M uller, "Methoden der Organischen Chemie (Houben-Weyl)" Band V1/2, Sauerstoffverbindungen l, 1965; pp. 19-20.

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