Lodonium ylides

Ylides other than acceptor-substituted diazomethanes have only occasionally been used as carbene-complex precursors. lodonium ylides (PhI=CZ Z ) [1017,1050-1056], sulfonium ylides [673], sulfoxonium ylides [1057] and thiophenium ylides [1058,1059] react with electrophilic transition metal complexes to yield intermediates capable of undergoing C-H or N-H insertions and olefin cyclopropanations. 

When these cycloaddition reactions are carried out with alkynes, furan derivatives are formed. lodonium ylide 5, for instance, on photochemical reaction with alkynes 43, gives benzofurans 44 (86JOC3453) (Eq. 19). In a similar way, the iodonium ylide derived from 2-hydroxy-1,4-naphthoquinone undergoes a cycloaddition reaction with phenylacety-lene to yield benzofuran 45 (Scheme 16) (89LA167). 

Table 2. Copper Salt Catalyzed Intramolecular Cyclopropanation Using lodonium Ylides Derived from 3-Oxohept-6-enoic Esters or /l-Oxobut-3-enyl Sulfones...

Intramolecular Cyclopropanation Using lodonium Ylides Typical Procedure "... 

Figure 2.15 lodonium ylides derived from cyclic 1,3-dicarbonyl compounds (405), phenols (406), coumarin derivatives (407) and hydroxyquinones (408). 

Figure 2.16 lodonium ylides analyzed by single-crystal X-ray diffraction. 

Another use of iodonium ylides is as a synthetic route to heterocyclic compounds (Scheme 9). lodonium ylides can be photochemically converted to oxathiole-2-thiones in the presence of CSj. In the presence of phenyl isothiocyanate or styrenes, the iodonium ylides undergo photochemical conversion to 2-phenyliminooxathioles, dihydrofurans, and dihydrobenzofurans, respectively. Many other interesting reactions of iodonium ylides based on the photochemical approach are also reported in the literature. 

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