Abstract: Preparation of alkoxymethylene malonic acid ester of formula: ##STR1## wherein R and each R' is an alkyl group, by reaction of malonic acid diester and ortho formic acid triester. The reaction is performed in the presence of a carboxylic acid or a carboxylic acid anhydride and a Lewis acid. The ortho ester is initially present in amount of at least 1,4 mols per mole of the malonic acid ester starting material. Alcohol formed during the reaction is removed during the reaction.

Abstract: A process for preparing a pyridylaminomethylenemalonic acid derivative of the formula: ##STR1## which comprises reacting together a pyridyl compound of the formula: ##STR2## an alkoxy compound of the formula: ##STR3## and a malonic acid derivative of the formula selected of the group of ##STR4## wherein: R.sub.5 and R.sub.7 are the groups -- OOR.sub.4 or OOR.sub.5 or .tbd.NR is a substituted or unsubstituted alkyl radical, preferably a C.sub.1 - C.sub.4 alkyl radical;R.sub.1, r.sub.2 and R.sub.3 are each independently substituted or unsubstituted alkyl radicals, preferably C.sub.1 - C.sub.2 alkyl radicals;R.sub.4 and R.sub.5 are each independently substituted or unsubstituted alkyl radicals, preferably C.sub.1 - C.sub.8 alkyl radicalsAt a temperature of 60.degree. to 160.degree. C.