Organic compounds -- part of the class 532-570 series – Organic compounds
Patent
1997-05-20
1998-07-14
Lambkin, Deborah C.
Organic compounds -- part of the class 532-570 series
Organic compounds
560 35, 562470, 562471, 564164, 564253, 564254, 564255, C07D29100, C07C22900, C07C 5940, C07C23300
Patent
active
057806241
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This appln. is a 371 of pct/EP95/04580 Nov. 21, 1995.
The present invention relates to a process for preparing oxime ethers of the general formula I ##STR4## where R.sup.1 is a C-organic radical, CO.sub.2 -alkyl, P(O)(OR.sup.4).sub.2 or a C-organic radical, and -alkyl, ##STR5## where the substituents R.sup.1 and R.sup.2 have the abovementioned meanings, in the presence or absence of an organic diluent, with a base into the corresponding salt, and reacting the latter with a dialkyl carbonate of the general formula III ##STR6## where R.sup.3 has the abovementioned meanings.
The present invention preferably relates to a process for preparing oxime ethers of the general formula Ia ##STR7## where R.sup.3, R.sup.4 are, identically or differently, C.sub.1 -C.sub.6 -alkyl and R.sup.4 is additionally hydrogen, and ##STR8## where R.sup.5 -R.sup.7 are, identically or differently, hydrogen, C.sub.1 -C.sub.4 -alkyl, aryl and hetaryl, with the proviso that following radicals: halogen, cyano, nitro, C.sub.1 -C.sub.4 -alkyl, C.sub.1 -C.sub.4 -alkoxy, C.sub.1 -C.sub.4 -haloalkyl, C.sub.1 -C.sub.4 -haloalkoxy, C.sub.1 -C.sub.4 -alkoximino-c.sub.1 -C.sub.4 -alkyl, aryl, aryloxy, benzyl, benzyloxy, hetaryl, hetaryloxy, C.sub.3 -C.sub.6 -cycloalkyl, C.sub.1 -C.sub.4 -dialkylamino, CO.sub.2 CH.sub.3, CO.sub.2 C.sub.2 H.sub.5, formyl and acetyl, and that such as dialkyl sulfate or alkyl halide ##STR9##
However, both process variants have considerable disadvantages which impede industrial preparation of the compounds of the general formula I. Particular mention should be made of the high price and the poor availability of alkoxyamine salts in process variant a).
The main disadvantage of variant b) is the low selectivity of the alkylation reaction; thus, besides the desired O-alkylation product, there is also obtained a 10-20% yield of the N-alkylation product in the form of the corresponding nitrone.
These two ways of preparing novel oxime ethers are described, for example, in EP-B 253 213.
EP-A 554 767 describes a process for preparing E-oxime ethers of phenylglyoxylic esters, in which E-oximes of phenylglyoxylic esters are reacted with an alkylating agent, also resulting in the corresponding nitrone, which is described in connection with procedure b), as by-product.
SUMMARY OF THE INVENTION
J. Chem. Soc. 58 (1993) 5765-70 discloses the reaction of aliphatic oximes with dimethyl carbonate to give essentially oxazolinones and only to a minor extent O-methyl derivatives. Reaction of benzophenone oxime with dimethyl carbonate resulted in 56% of the oxime methyl ether and 24% of the N-methylnitrone. Reaction of acetophenone with dimethyl carbonate resulted in 45% of the corresponding O-methyl derivative. This document shows that reaction of oximes with dimethyl carbonate has low selectivity in respect of oxime ether formation.
It is an object of the present invention to find a simple, low-cost and industrially applicable process for preparing the oxime ethers I.
We have found that this object is achieved by very selective alkylation of an oxime of the general formula II in the desired manner on the oxygen atom using a dialkyl carbonate in the presence of a base. The unwanted by-product formed by alkylation on the oxime nitrogen atom (nitrone) is produced in a maximum yield of 5% in the present process, but as a rule in a yield of <2%.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The process according to the invention is, as a rule, carried out in such a way that an oxime of the general formula II is initially reacted with a base, and the oximate which is formed is then reacted with dialkyl carbonate at 80.degree.-130.degree.C., preferably at the boiling point of the particular dialkyl carbonate.
It is often advantageous to isolate the oximate which is formed and then to react it in pure form with a dialkyl carbonate, preferably with dimethyl carbonate, at 80.degree.-130.degree. C., preferably at the boiling point of the particular dialkyl carbonate. It is preferable in this
REFERENCES:
patent: 5354883 (1994-10-01), Isak et al.
J. Org. Chem., vol. 58, No. 21, 1993, pp. 5765-5770.
ACS Symposium Series, vol. 443, 1991, pp. 226-235.
Keil Michael
Wingert Horst
BASF - Aktiengesellschaft
Lambkin Deborah C.
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