An Approach Toward Oxidopyrylium Ylides Using Rh(II)-Catalyzed Cyclization Chemistry.

The Rh(II)-catalyzed reaction of the E-isomer of 2-diazo-3,6-dioxo-6-phenyl-hex-enoic acid methyl ester was carried out in the presence of various carbonyl compounds and was found to give 1,3-dioxoles in moderate to good yield. In an attempt to prepare the starting -diazo substrate, an unexpected pseudo-dimerization reaction was encountered when 5-phenyl-furan-2,3-dione was heated in the presence of sodium methoxide.