Carbomethoxy iodonium ylides, generated from methyl acetoacetate and methyl malonate, respectively, are exploited in synthesis of cyclopropanes, cyclopropenes as well as various heterocycles. Despite the fact that a significant number of iodonium ylides, 1 a class of hypervalent iodine compounds, are known in the literature, their chemistry still remains unexplored, especially when compared to the corre-sponding diazo compounds. 2 Generally speaking, the easily isolable 3 phenyliodonium ylides, formed quanti-tatively from the reaction of an active methylene com-pound and a hypervalent iodine precursor, have often been used as alternatives to diazo precursors in metal-catalyzed or photochemical cycloadditions and CH insertion reactions. 4 These reactions occur sometimes in the absence of catalysts, albeit in much lower yields. Quite generally speaking, phenyliodonium ylides usu-ally decompose at lower temperatures than the corre-sponding diazo compounds, thus leading to better yields of the desired products. The major drawback of iodonium ylide chemistry, is the requirement for two similar strong electron-with-drawing substituents at the carbanionic center. Gener-ally, such ylides are isolable in pure form, while ylides with different carbanionic substituents are rather labile entities with unknown behavior. Ylides 2, bearing at least one carbomethoxy substituent were easily prepared from methyl acetoacetate 1a and methyl malonate 1b, respectively, in moderate yields (Scheme 1), employing the well-known procedure. 3,4b There are two IC bonds which could, in principle, be cleaved. Cleavage of the IC aromatic bond could yield an iodo ether 3, resembling the decomposition product of a b-dicarbonyl iodonium ylide, while the cleavage of the IC carbanionic bond could yield initially a carbene (or