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

Methyl 2-oxo-2-arylacetates 1, which include some fluorinated compounds, ha ve been synthesized in moderate to excellent yields by reaction of methyl o xalyl chloride with arylzinc halides in the presence of Pd(PPh3)(4). The hi ghest yields have been obtained when these reactions involved arylzinc brom ides which were prepared by conversion of the corresponding aryl bromides t o organolithiums, followed by transmetallation with ZnBr2. Compounds 1 have been converted in high yields to the corresponding (E)- and (Z)-O-methylox imino-2-arylacetates (E)- and (Z)-5 by treatment with O-methylhydroxylamine hydrochloride in pyridine. Compounds (E)and (Z)-5 have been easily separat ed by MPLC on silica gel and their structure and stereochemistry have been assigned by NMR techniques. So prepared compounds of general formula 5 incl uded an agrochemically important fungicide, i.e. (E)-5c, its fluorinated st ructural analogues, as well as compounds which proved to be able to delay t he growth of fungal species isolated from deteriorated papers. Interestingl y, several compounds of general formula (Z)-5 underwent partial stereomutat ion in the presence of daylight and catalytic amounts of iodine. (C) 1999 E lsevier Science Ltd. All rights reserved.