1999 stereochemistry

stereochemistry (general, optical resolution)O 0030

44 - 034Transition-Metal-Catalyzed Carbenoid Reactions of SulfoniumYlides. — The Rh(II)- and Cu(I)-catalyzed decomposition of diphenyl-sulfonium methylide (II) in the presence of various olefins is studied in orderto develop a synthetic alternative for carbenoid olefin cyclopropanation thatreplaces toxic and explosive diazo compounds. For comparison the samereactions are studied using diazoacetate (V). The product distribution forthe Rh(II)- and Cu(I)-catalyzed reactions of (II) and diazo compound (V)is practically identical, which suggests that both types of compounds reactvia the same mechanism. However, the reactions of (II) suffer generally fromsignificantly lower yields in comparison to those of diazo compound (V). Thetrans/cis ratios of cyclopropanes change slightly upon going from methylide (II)to diazoacetate (V) by Rh(II) catalysis, as well as the enantioselectivities by useof chiral Rh catalyst. In the presence of chiral Cu catalyst, the trans/cis ratiosand enantioselectivities are almost identical. Intramolecular Rh(II)-catalyzedcarbenoid reactions are demonstrated for compounds (V) and (VII) which givethe expected products with good enantioselectivities. — (MUELLER, PAUL;FERNANDEZ, DANIEL; NURY, PATRICE; ROSSIER, JEAN-CLAUDE;Helv. Chim. Acta 82 (1999) 6, 935-945; Dep. Org. Chem., Univ. Geneva,CH-1211 Geneva 4, Switz.; EN)

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1999 stereochemistry

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