Structure data, alkynyliodonium salts

The pareitropone project began quite by accident after an unexpected observation expanded our thinking about potentially accessible targets for alkynyliodonium salt/alkylidenecarbene chemistry (Scheme 18). Treatment of the tosylamide iodonium salt 125 with base under standard conditions was designed to provide no more than routine confirmation of the aryl C-H insertion capabilities, which were first exposed in indoleforming reactions using tosylanilide anion nucleophiles and propynyl(phenyl)iodonium triflate,5b of the intermediate carbene 126. However, this substrate did not perform as expected, since only trace amounts of the 1,5 C-H insertion product 127 was detected. One major product was formed, and analysis of its spectral data provided yet another surprising lesson in alkynyliodonium salt chemistry for us. The data was only consistent with the unusual cycloheptatriene structure 129. 

Single-crystal X-ray structures of six alkynyliodonium compounds, all containing oxyanions and including four alkynyl(phenyl)iodonium salts, one alkynylbenziodoxolone and one dialkynyliodonium salt, have been reported. Selected structural data for these compounds are given in Table 3. 

TABLE 3. Selected X-ray structural data for alkynyliodonium salts... 

To date, six single-crystal X-ray molecular structures of alkynyliodonium compounds have been reported four aIkynyl(phenyl)iodonium salts including the substituted cyanoethynyl salt, one heterocyclic and one dialkynyliodonium salt, all with oxyanions. Key structural data for these compounds are summarized in Table 3-1. 

Table 3-1 Key X-Ray Molecular Structural Data for Alkynyliodonium Salt...

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