Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1997-01-21
1998-11-03
Richter, Johann
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
568463, 568464, C07C 4545, C07D24908
Patent
active
058310975
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/EP95/02660 filed Jul. 8, 1995.
DESCRIPTION
The present invention relates to a process for the preparation of acyloins of the general formula I ##STR3## in which R.sup.a and R.sup.b are the same or different and stand for hydrogen or an optionally substituted C.sub.1 -C.sub.20 alkyl, an optionally substituted C.sub.6 -C.sub.10 aryl, an optionally substituted C.sub.7 -C.sub.12 aralkyl, an optionally substituted heteroaryl, or an optionally substituted heterocycloalkyl group, except for autocondensation products of formaldehyde.
In addition, the present invention relates to a process for the preparation of cycloaliphatic or heterocycloaliphatic acyloins having a total of from 5 to 12 ring members.
In addition, the present invention relates to a process for the preparation of acyloins of the general formula Ia ##STR4## in which the radicals R.sup.a' and R.sup.b' are different and stand for hydrogen or an optionally substituted C.sub.1 -C.sub.20 alkyl, an optionally substituted C.sub.6 -C.sub.10 aryl, an optionally substituted C.sub.7 -C.sub.11 aralkyl, an optionally substituted heteroaryl, or an optionally substituted heterocycloalkyl group, except for autocondensation products of formaldehyde.
Since the publication of papers by Breslow (J. Am. Chem. Soc. 80, 3719 (1959)) it is known that thiazolium ylides can be used as catalysts for the catalytical reversal of polarization of aldehydes and thus for their condensation to form acyloins. Castells (Tetrahedron lett. 21, 4517 (1980)) applied this reaction to the autocondensation of formaldehyde. .alpha.-hydroxycarbonyl compounds are generally designated as acyloins, in particular .alpha.-hydroxyketones and .alpha.-hydroxyaldehydes. The said processes have considerable disadvantages however. Thus relatively large amounts of the thiazolium ylide serving as catalyst, that is to say from 5 to 20 mol %, based on the aldehyde used, are required in order to achieve a satisfactory space-time yield. In addition, the thiazolium ylide catalysts have been found to be relatively unstable during continuous operation, ie they form considerable quantities of decomposition products of the thiazolium ylide catalyst which are virtually impossible to separate from the desired product. These factors are an obstacle to the use of the thiazolium ylide catalysts in industrial processes.
DE-A 4,230,466 relates to a process for the preparation of autocondensation products of formaldehyde by means of triazolium salt catalysts. Formaldehyde used in this process as starting material is the simplest of the aldehydes but is unique, as aldehyde, in respect of its chemical behavior, particularly as regards its high chemical reactivity. The same applies, on account of their special chemical structure, to the formaldehyde/triazolium salt adducts formed as intermediates in this process. In addition, in the condensation of formaldehyde with itself there is virtually no sterical hindering of the reactants. This document makes no reference to the applicability of this process to the condensation of aldehydes higher than formaldehyde.
Acyloins are very well suited, on account of their bifunctionality (carbonyl and hydroxy group in mutual .alpha.-position relationship), for the synthesis of heterocyclics, in particular imidazoles (EP-A 252,162) and imidazolones (J. Chem. Soc. Perkin II, 310 (1981)), which are in turn used, eg, in the preparation of medicines and plant protectants and are thus desirable intermediates and building blocks for the preparation of such active materials. On account of their high reducing power, acyloins are used as reducing agents in the dyeing industry, for example for dyeing textile materials consisting of cellulose fibers (EP-A 364,752). Further applications of acyloins are given below by way of example:
Acetoin is used, eg, as an aromatic substance in foodstuffs, likewise the diacetyl obtainable therefrom by oxidation. Furoin serves as starting material for the preparation of furildioxime, which is obtained therefrom by its oxidation to
REFERENCES:
patent: 3957888 (1976-05-01), Reiss et al.
patent: 4035395 (1977-07-01), Stetter et al.
patent: 4482696 (1984-11-01), Schuster et al.
patent: 5386062 (1995-01-01), Teles et al.
Tetrahedron Letters, vol. 21, pp. 4517-4520, (1980).
J. Am. Chem. Soc., vol. 80, pp. 3719-3726, (1958).
J. Chem. Soc., Perkin II, pp. 310-316.
Ebel Klaus
Melder Johann-Peter
Schneider Regina
Teles Joaquim Henrique
BASF - Aktiengesellschaft
Oswecki Jane C.
Richter Johann
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