Process and intermediate products for preparing substantially isomer-pure E-2(2-aryloxymethylene phenyl)-crotonic acid methyl esters

摘要

PCT No. PCT/EP96/01689 Sec. 371 Date Oct. 9, 1997 Sec. 102(e) Date Oct. 9, 1997 PCT Filed Apr. 23, 1996 PCT Pub. No. WO96/34847 PCT Pub. Date Nov. 7, 1996A process for the preparation of essentially isomerically pure methyl E-2-(2-aryloxymethylenephenyl)crotonates of the formula Ia <IMAGE> Ia where R is an aromatic radical and R' is a C1-C3-alkyl group, which comprises first converting a suitable methyl 2-(2-aryloxymethylenephenyl)- alpha -ketoacetate with an alkyl metal compound of the formula IIIM-CH2-R'IIIwhere M is a metal ion equivalent into the corresponding methyl 2-(2-aryloxymethylenephenyl)- alpha -hydroxybutyrate of the formula IV, subsequently dehydrating IV in the presence of an acid to give a mixture of methyl E- and Z-2-(2-aryloxymethylenephenyl)crotonates and, subsequently, converting this mixture in the presence of a base in an inert polar solvent into the essentially isomerically pure methyl E-2-(2-aryloxymethylenephenyl)crotonate Ia.