Control of Chemoselectivity in Dirhodium(II)-Catalyzed Reaction of 5, 6-Dioxygenated 2-Diazo-3-oxohexanoates : C-H Insertion Reaction versus Oxonium Ylide Formation

Abstract

Methyl (S)-2-diazo-4-(3, 3-dimethyl-2, 4-dioxolan-1-yl)-3-oxobutanoate (1), upon treatment with Rh₂(OAc)₄ in boiling dichloromethane, gave methyl (1S, 5S)-2, 2-dimethyl-7-oxo-3, 8-dioxabicyclo[3.2.1]octane-1-carboxylate (2) via oxonium ylide formation/1, 2-shift. On the other hand, similar treatment of methyl (S)-5, 6-bis(tert-butyldimethylsilyloxy)-2-diazo-3-oxohexanoate (3a) gave methyl 3-(tert-butyldimethylsilyloxy)-5-oxo-1-cyclopentene-1-carboxylate (4a) via the C-H insertion reaction.