Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
2000-01-27
2000-10-17
Ramsuer, Robert W.
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C07D23122
Patent
active
061334510
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/EP98/04490 filed Jul. 20, 1998.
The present invention relates to a process for preparing 2-(3-pyrazolyloxymethylene)nitrobenzene derivatives of the formula I ##STR4## where R.sup.1 is halogen; alkoxycarbonyl; carbocyclyl or heterocyclyl; different when m is greater than 1; different when n is greater than 1; ##STR5## where R.sup.1 has the abovementioned meaning, to give the o-nitrobenzyl bromide of the formula III ##STR6## in the presence of a nonpolar aprotic solvent and subsequent reaction of the resulting solution of III with a 3-hydroxypyrazole of the formula IV ##STR7## where R.sup.2 and R.sup.3 have the abovementioned meanings, in the presence of a base.
Numerous processes for preparing o-nitrobenzyl bromides of the formula III starting from o-nitrotoluene derivatives II are described in the literature. In many cases, owing to the deactivation by the nitro group, the side-chain bromination takes place only at temperatures above 100.degree. C. and under pressure. These conditions are disadvantageous in view of the low thermal stability of the o-nitrobenzyl bromides and are problematic in terms of industrial safety (see Z. Chem. 12 (1972) 139).
WO 96/01256 describes the preparation of 2-(3-pyrazolyloxy-methylene)nitrobenzene derivatives I starting from o-nitrobenzyl bromides III in general. No details are given of the industrial preparation of III in this publication. Nor does the publication provide any help with safe handling of III on implementation of the described process on the industrial scale. The handling of industrial quantities of III is problematic because of the lachrymatory and mucosal-irritant effect of III and the thermal instability of III which has already been mentioned.
It is an object of the present invention to find a route to 2-(3-pyrazolyloxymethylene)nitrobenzene derivatives I which is industrially applicable and, on the one hand, solves the difficult operating and safety problems in handling III and, on the other hand, provides the required product I in good yield and purity. Compounds of the formula I are important intermediates for preparing inter alia the fungicidal agents described in WO 96/01256.
We have found that this object is achieved by the process mentioned at the outset, wherein the solution of the o-nitrobenzyl bromide III resulting from the bromination is reacted further with IV, in the solvent used, directly without intermediate isolation of the o-nitrobenzyl bromide III.
Surprisingly, the novel process provides the required compound I in good yield and in excellent purity. This was not to be expected since the bromination always takes place with formation of considerable quantities of o-nitrobenzal bromide V, which is able to react with 3-hydroxypyrazoles IV to give bis-O-alkylated acetals of the formula VI. ##STR8##
The formation of VI can be virtually completely suppressed by employing the 3-hydroxypyrazole IV, which is the more costly component, in equimolar quantities, or even less, relative to the o-nitrobenzyl bromide III. The selectivity of the alkylation reaction is surprising; on the contrary, the substrates o-nitrobenzyl bromide III and o-nitrobenzal bromide V would have been assumed to be of comparable reactivity.
The novel process can be used to prepare 2-(3-pyrazolyloxy-methylene)nitrobenzene derivatives of the formula I. The meanings specified above for the substituents R.sup.1 to R.sup.3 in formula I represent collective terms for individual lists of single members of the groups. All alkyl moieties may be straight-chain or branched. Halogenated substituents preferably have from 1 to 6 identical or different halogen atoms.
Examples of specific meanings are:
halogen: fluorine, chlorine, bromine and iodine;
alkyl or the alkyl moieties of alkoxy, alkoxycarbonyl and alkylthio: saturated, straight-chain or branched hydrocarbon radicals, in particular having 1 to 10 carbon atoms, eg. C.sub.1 -C.sub.6 -alkyl such as methyl, ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, pentyl, 1-m
REFERENCES:
Recueil des Travaux (Chimiques des Pays-Bas, Bd., 107/2, 1988 73-81, van den Berge et al.
Gotz Norbert
Keil Michael
Klintz Ralf
Vogelbacher Uwe Josef
Wahl Josef
BASF - Aktiengesellschaft
Ramsuer Robert W.
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