Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Patent
1987-07-16
1990-01-09
Garner, Vivian
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
260408, 2604109R, 131276, 426538, 512 8, 568346, 568379, 568380, C07C 69716
Patent
active
048929662
DESCRIPTION:
BRIEF SUMMARY
The invention is concerned with a novel process for the manufacture of .alpha.-hydroxycarbonyl compounds, especially those of the formula ##STR3## wherein R.sup.1 signifies C.sub.1-5 -alkyl, especially methyl, ethyl, propyl or isopropyl, and the radicals R.sup.2 each independently represent hydrogen or C.sub.1-5 -alkyl, especially hydrogen or methyl, ethyl, propyl or isopropyl.
The process in accordance with the invention is characterized in that a compound of the general formula ##STR4## wherein R stands for C.sub.1-4 -alkoxy, chlorine, bromine or C.sub.1-4 -alkanoyloxy, e.g. acetoxy, propionyloxy, butyryloxy, R.sup.1 and R.sup.2 have the above significance and R.sup.3 represents C.sub.1-4 -alkyl, is hydrolyzed and subjected to an aldol condensation.
In this alkaline hydrolysis the ester bonds which are present in II (R in II=C.sub.1-4 -alkanoyloxy and the group --COOR.sup.3) are cleaved. The aldol condensation yields the compound I.
Where R=chlorine or bromine, only the group --COOR.sup.3 is initially cleaved hydrolytically and, after the aldol condensation has been carried out, the halogen residue R must also be hydrolyzed alkalinically.
As the aldol condensation is preferably carried out alkalinically, where R=C.sub.1-4 -alkoxy the compound ##STR5## wherein R.degree. stands for C.sub.1-4 -alkyl and R.sup.1 and R.sup.2 have the above significance, which is initially formed in this manner must, of course, thereupon be subjected to an acidic ether cleavage.
Tautomerism is possible where R.sup.1 .noteq.R.sup.2 .noteq.H. Formula I is accordingly intended to embrace both tautomeric forms and their mixtures.
The convenient parameters for the process in accordance with the invention, i.e. the conversion in accordance with the invention of II into I, are indicated in the following Reaction Scheme and Table I relating thereto.
Moreover, this Scheme and Table I contain the convenient parameters for the process for the preparation of the compounds II.
In this Scheme:
The novel compounds II are obtained by alkylating a compound of the formula ##STR6##
wherein R, R.sup.2 and R.sup.3 have the above significance, conveniently by means of halocarbonyl compounds in accordance with the Reaction Scheme.
In a particular embodiment in the case of R.sup.2 .dbd.C.sub.1-5 -alkyl (R.sup.2 in the .alpha.-position to the ester group) a corresponding compound III is not used, but the compound of formula II is alkylated prior to its hydrolysis and the aldol condensation which are conveniently carried out without separating the alkylated product. ##STR7##
Table I provides information concerning convenient methods and reagents as well as convenient and preferred reaction parameters for the individual process steps.
TABLE 1 __________________________________________________________________________
Type of
Step
reaction
Reagent T Literature
__________________________________________________________________________
a 1
Hydrolysis (1)
Metal hydroxides, metal carbon-
20-100.degree. C.
H.O. House, Modern Synthetic
a 3
alkaline
ates, metal bicarbonates
Reactions, 2nd ed. W. A.
(ester cleav-
in aqueous solution Benjamin Inc. Menl. Park,
age) California, 1972, 511 seq.,
concomitant 629 seq.
aldol conden-
sation
a 11
Enol-ether
Strong acids e.g. H.sub.2 SO.sub.4,
Reflux
H.O. House loc, cit. 504
cleavage (1)
HCl, H.sub.3 PO.sub.4
temper-
aqueous solution;
ature
HI, HBr/CH.sub.3 COOH
a 2
Hydrolysis (1)
Alkaline conditions:
20-100.degree. C.
Metal hydroxides, e.g. alkali
metal hydroxides, alkaline
earth metal hydroxides,
preferably in aqueous solution.
aqueous ammonia solution
a 22
Hydrolysis (1)
Weakly basic: 20-100.degree. C.
H.O. House, loc. cit.,
alkaline
Metal carbonates, metal bi-
511 seq., 629 seq.
(ester cleav-
carbonates
age) in aqueous solution
concomitant
aldol conden-
ation
b 1
Substitution
Alkali alcoholate in excess:
prefer-
EP-PS 76,378
(alkoxylation)
aprotic solvent, e.g.
ably CH-PS 562,191
acetonitrile, prop
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Garner Vivian
Givaudan Corporation
Tavares Robert F.
Vag Linda A.
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