Process for preparing substituted valine amide derivatives

Details Process for preparing substituted valine amide derivatives Process for preparing substituted valine amide derivatives

1999-01-28

2000-06-20

Richter, Johann

Organic compounds -- part of the class 532-570 series

Organic compounds

Carboxylic acid esters

C07C26904, C07C27114, C07C27118

Patent

active

060779691

DESCRIPTION:

BRIEF SUMMARY
The invention relates to valinamide derivatives and a process for their preparation.
The valinamide derivatives are known and have excellent effectiveness in pest control. In particular, they can be used as fungicides, especially in crop protection (EP-472 996).
It has now been found that the known valinamide derivatives can be prepared more simply and with higher yield and purity, it being possible to essentially dispense with the use of organic solvents.
The application thus provides a process for the preparation of compounds of the formula (I) ##STR1## in which
R.sup.1 is i-propyl or s-butyl, and
R.sup.2 is chlorine, methyl, ethyl or methoxy, chloroformate, and the resulting reaction products, after neutralization, presence of catalytic amounts of a tertiary amine reacted with isopropyl chloroformate, and then the resulting reaction products, optionally after the addition of organic solvents, dissolved in organic solvents, at least one organic solvent being used in process step b) or process step c).
The valinamide derivatives obtainable by this process can be readily worked up and isolated and are produced in compact form with a high space/time yield.
The process according to the invention or the individual process steps a) and b) are preferably carried out in water as the sole solvent or diluent respectively.
The products of process steps a) and b) can be isolated and used for further reaction. However, the process is preferably carried out without intermediate isolation as a one-pot process, optionally with return of the mother liquor to a further batch or optionally with continuous processing.
For the process steps a) and b), isopropyl chloroformate is preferably used. The ester is preferably added to the corresponding solutions or reaction mixtures, the ester preferably being added in molar excess based on valine or the reaction product from process step a) and in total amounts of from 2 to 3 mol, based on 1 mol of valine.
The addition or reaction temperatures for process step a) are preferably from -20 to 80.degree. C., in particular from 10 to 50.degree. C., and for process step b) preferably from -20 to 40.degree. C., in particular from 10 to 30.degree. C. Process steps a) and b) are preferably carried out at room temperature, optionally with cooling of the exothermic reaction.
Process step a) is carried out in an alkaline medium, i.e. preferably in the presence of inorganic bases such as KOH and, in particular, NaOH. The base is in excess, in particular, in an amount from 1 to 3 mol, based on 1 mol of valine.
The neutralization in process step a) is preferably carried out using inorganic acids such as sulphuric acid and, in particular, hydrochloric acid, in particular to a pH of about 7.
Process step b) is carried out in the presence of catalytic amounts of a tertiary amine, preferably pyridine, methylpyridine, dimethylaminopyridine, triethylamine and/or, in particular, dimethylbenzylamine (Desmorapid DB.RTM.). In the present application, catalytic amounts are preferably taken to mean amounts of 1/10,000 to 1/100 mol of catalyst per mol of valine.
It is particularly important for process step c) and for subsequent work-up that the phenethylamines are dissolved in little organic solvent and brought to react only with the reaction products from process step b).
The solvents used are preferably acetic ester, methyl tert-butyl ether and, in particular, tert-amyl methyl ether (TAME). The amount of organic solvent used is preferably from 50 to 800 ml and, in particular, from 100 to 500 ml, based on 0.3 mol of the respective phenethylamine. The phenethylamines predissolved in this way are then preferably added to the reaction mixture from process step b), the amount of phenethylamine being equimolar or in slight excess relative to valine.
For better work-up of the target compounds produced in process step c), the reaction mixtures from process step c), are heated to temperatures of from 40.degree. C. up to the boiling temperature of the respective organic solvent, optionally under pressure, until opti

REFERENCES:
patent: 5453531 (1995-09-01), Seitz et al.
M. R. Vernsten et al: "The Preparation of Some N-Carbethoxyamino Acids", Mar. 1953, DC US, 1320-1321, XP002046973, Journal of the American Chemical Society.
Database CAPLUS on STN, Acc. No. 108:38389, Chen et al., `Diisopropylethylamine eliminates dipeptide formation during the acylation of amino acids using benzoyl chloride and some alkyl chloroformates.` Can. J. Chem (1987), 65(6), pp. 1224-1227 (abstract), 1987.

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