Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Patent
1996-03-04
1999-11-09
Ambrose, Michael G.
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
568 62, 568 66, 568861, 568862, C07C 29147, C07C 29143, C07C 2914, C07C31902, C07C31912
Patent
active
059818093
DESCRIPTION:
BRIEF SUMMARY
The field of the invention is that of enantiomers, in particular difunctional ones, of high optical purity.
This purity is particularly interesting and advantageous in view of the optimum expression of the functionalities of the enantiomers, especially as reactants, synthons or intermediates in specific syntheses of chiral compounds such as active ingredients, e.g. pharmaceutical or agrochemical ones, or as active compounds per se or else as precursors of special polymers.
More precisely, the present invention relates to the synthesis of difunctional compounds of high enantiomeric purity and of formula: ##STR1## in which: ##STR2## R.sub.1 and R.sub.2 are identical or different and denote hydrogen or an aliphatic and/or alicyclic and/or aromatic and/or heterocyclic hydrocarbon radical, preferably a hydrogen or an alkyl, group, corresponds to the formula (If) in which: ##STR3## with R.sub.2 and Y as defined above, it being additionally possible for R.sub.2 to denote an NH.sub.2, alkoxy, or alkylated S radical or: ##STR4## with n=1 to 1000.
Still more precisely the present invention relates to the synthesis of enantiomers of high optical purity containing at least two hydroxyl functional groups (diols) or two thiol functional groups (dithiols).
A nonlimiting example of a diol is (+)(S)-1,2-propanediol or (-)(R)-1,2-propanediol.
To obtain enantiomers of high optical purity the operation is conventionally carried out by resolving the racemate: a chemical or enzyme route. The chemical route is essentially that of converting the racemate to two separable diastereoisomers. Separation by liquid phase chromatography or by crystallization may be mentioned.
These chemical resolutions are cumbersome, complex and therefore costly to implement.
The same applies to enzyme resolutions which, in addition, present the disadvantage of being specific to a given enantiomer.
Routes for specific asymmetric chemical synthesis are also known, like, for example, the asymmetric dihydroxylation of propene, catalysed by osmium tetraoxide and making it possible to obtain one of the enantiomers of 1,2-propanediol (K. B. Sharpless et al., J.O.C., 1992, 57, 2768), with an enantiomeric purity which remains moderate.
Another, more advantageous, possibility of obtaining compounds of high enantiomeric purity, which are capable of being exploited industrially, consists in employing chiral compounds as starting materials, like, for example, those corresponding to the formula (Id) given above, and in reducing them so as to produce the hydrogenated derivatives of high enantiomeric purity which are aimed at (If).
By definition, the chiral materials (Id) are inexpensive, being easily available or accessible. They may be materials which are present in nature and are easily extractable, or else compounds that can be produced in industrial quantities, e.g. by fermentation or resolution. These materials (Id) are, for example, esters of .alpha.-, .beta.- or .gamma.-hydroxycarboxylic acids or of other derivatives of the latter, such as ketones or aldehydes, as well as their equivalents, when sulphur is substituted for oxygen in the radicals X and Y.
Among these techniques employing a reduction, those using catalytic reduction under hydrogen will be adopted, as well as those using stoichiometric reduction with the aid of a chemical reducing agent.
Insofar as the catalytic reduction under hydrogen is concerned, the prior technical literature bears witness to the great difficulties that exist in reducing an acid, an ester, an aldehyde, a ketone, or their sulphur analogues, to alcohol or thiol in conditions that are mild and productive. The catalysts employed in heterogeneous catalysis are generally Raney nickel and copper chromites.
By way of example, the paper by E. Bowden et al., JACS, 56, 689, 1934, may be cited, which is one of the only ones to be concerned with chirality and which reports a total racemization when (+)n-butyl lactate is subjected to reduction by heterogeneous catalysis with the aid of copper chromite (200 bars-225.degree. C.-2 hours in b
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Melchiorre, C. "A Convenient Synthesis of S(+)-propane-1,2-diol." Chemistry and Industry (Mar. 6, 1976): 218.
Gombos, J. et al. "Notiz uber eine einfache Herstellung von (S)-Propylenoxid." Chem. Ber. (1976): 109, 2645-2647.
Ambrose Michael G.
Rhone-Poulenc Chimie
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