C - Chemistry – Metallurgy – 07 – D
Patent
C - Chemistry, Metallurgy
07
D
C07D 241/44 (2006.01) A01N 43/60 (2006.01) C07D 403/12 (2006.01) C07D 405/12 (2006.01)
Patent
CA 2058320
HOE 90/F391 Abstract Process for the preparation of optically active esters of quinoxalinyloxyphenoxypropionic acid The invention relates to a process for the preparation of o p t i c a l l y a c t i v e e s t e r s o f (D)-2-[4-(quinoxalinyloxy)phenoxy]propionic acid of the formula I (selective herbicides) Image (I) in which R1 is H, halogen, haloalkyl, CN, NO2, alkyl or alkoxy, R2 is H or halogen, R3 is C1-C18alkyl, benzyl, cycloalkyl, optionally halogenated alkenyl, optionally halogenated alkynyl or (CH2)n(O)mR4, R4 is C1-C6-alkyl which may be substituted by alkoxy, or a 5- or 6-membered carbocyclic or heterocyclic compound or N=CR5R6, R5 and R6 are alkyl, cycloalkyl, alkylcarbonyloxyalkyl, alkoxy, alkylthio or, together with the carbon atom to which they are bonded, a cycloalkyl radical, n is 1 or 2 and m is 0 or 1, which comprises reacting a substituted quinoxaline of the formula II Image Image II III in which X is a leaving group, with a compound of the formula III in which R7 is C1-C4-alkyl, and, where R3 is not identical to R7, transesterifying the ester to obtained, of the formula I (R3=R7), to give another ester of the formula I substantially without racemization.
Mildenberger Hilmar
Zeiß Hans-Joachim
Fetherstonhaugh & Co.
Hoechst Aktiengesellschaft
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