2000 oxocarboxylic acids and esters

oxocarboxylic acids and esters (benzene compounds)Q 0460

01 - 101A Novel Method for the Efficient Synthesis of Methyl 2-Oxo-2-arylacetates and Its Application to the Preparation of Fungici-dal Methyl (E)-O-Methyloximino-2-arylacetates and Their (Z)-Stereoisomers. — Palladium-catalyzed reaction of methyl oxalyl chloride(II) with in situ prepared arylzinc halides provides a novel general access tothe title oxoarylacetates (III) and (VIII). It is shown that arylzinc bromides,derived from aryllithium compounds [from (VII)] and zinc bromide, possesshigher reactivity to methyl oxalyl chloride compared to arylzinc chlorides, whichare derived from Grignard reagents (I) and zinc chloride. Keto esters (III) and(VIII) are smoothly converted to E/Z-mixtures of the corresponding oximinoesters (V)/(VI) and (IX)/(X), resp., on reaction with O-methylhydroxylamine.E-oximino esters (V) and (IX) represent potential agrochemically useful fungi-cides. An attempt to transform the Z-isomers (VI) and (X) to their E-isomers,however, under daylight in the presence of catalytic iodine furnishes unevenresults. — (ROSSI, RENZO; CARPITA, ADRIANO; PAZZI, PIERGIOR-GIO; MANNINA, LUISA; VALENSIN, DANIELA; Tetrahedron 55 (1999) 37,11343-11364; Dip. Chim. Chim. Ind., Univ. Pisa, I-56126 Pisa, Italy; EN)

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