A novel method for the efficient synthesis of methyl 2-oxo-2- arylacetates and its application to the preparation of fungicidal methyl (E)- O-methyloximino-2-arylacetates and their (Z)-stereoisomers

Article abstract of DOI:10.1016/S0040-4020(99)00632-8

Methyl 2-oxo-2-arylacetates 1, which include some fluorinated compounds, have been synthesized in moderate to excellent yields by reaction of methyl oxalyl chloride with arylzinc halides in the presence of Pd(PPh₃)₄. The highest yields have been obtained when these reactions involved arylzinc bromides which were prepared by conversion of the corresponding aryl bromides to organolithiums, followed by transmetallation with ZnBr₂. Compounds 1 have been converted in high yields to the corresponding (E)- and (Z)-O- methyloximino-2-arylacetates (E)- and (Z)-5 by treatment with O- methylhydroxylamine hydrochloride in pyridine. Compounds (E)- and (Z)-5 have been easily separated by MPLC on silica gel and their structure and stereochemistry have been assigned by NMR techniques. So prepared compounds of general formula 5 included an agrochemically important fungicide, i.e. (E)-5c, its fluorinated structural analogues, as well as compounds which proved to be able to delay the growth of fungal species isolated from deteriorated papers. Interestingly, several compounds of general formula (Z)- 5 underwent partial stereomutation in the presence of daylight and catalytic amounts of iodine.