A new synthesis of fungicidal methyl (E)-3-methoxypropenoates

Several structural analogues of strobilurin A having general formula (E)-18, in which the methyl (E)-3-methoxypropenoate unit is linked to substituted aromatic, alkenyl or cyclopentenyl substrates, have been efficiently and selectively prepared by Pd-catalyzed cross-coupling reactions between (Z)-2-methoxy-1-(methoxycarbonyl)ethenylzinc halides, (Z)-19, and aryl halides, alkenyl halides or triflates or cyclopentenyl triflates, respectively. Compounds (Z)-19, which represent a new class of highly functionalized and stereodefined organozinc derivatives, have been synthesized in very high yield by reaction of THF solutions of easily available methyl (Z)-2-iodo- or (Z)-2-bromo-3-methoxypropenoate, (Z)-8 and (Z)-12, respectively, with an activated Zn/Ag couple in the presence of TMEDA. Compounds (E)-18 synthesized according to this procedure include substances which are known to be able to control agrochemically important fungi as well as derivatives which are able to inhibit the growth of fungi which deteriorate papery materials.