✍ Scribed by Spyroudis, Spyros P.
No coin nor oath required. For personal study only.
Photoreaktionen von 2,4-Dinitro-6-(phenyliodonio)phenolat mit einigen Nucleophilen 2,4-Dinitro-6-(phenyliodonio)phenolat (1) kann photochemisch mit Pyridin zu einem Pyridinium-Zwitterion 4, mit Phenylisocyanat zu einem 1,3-Benzoxathiol 5 und mit Thioharnstoffen zu h3-Iodanen 6 umgesetzt werden. Ein denkbarer Mechanismus wird vorgeschlagen.
The oxidodiaryl iodonium zwitterion 1 belongs to one of the two major classes of zwit-terionic iodonium compounds (ZIC), the other being aryliodonium ylides of active methylene compounds. The chemistry of ZIC has recently been reviewed 'I. Among oxidodiaryl iodonium zwitterions 2,4-dinitro-6-(phenyliodonio)phenolate (1) is easily prepared and fairly stable'). One of its most interesting properties is the nucleophilic displacement of the positive iodophenyl group by basic nucleophiles such as CH30Q, CH3CH2O0, BuNH2, OHQ already at room temperature. At higher temperatures a rearrangement of the zwitterion to iodophenyl ether predominates, as it also occurs with other zwitterions ' 1.
Another type of reaction of ZIC is that with heterocumulenes to form a range of various heterocycle^^^^). We have found that the yield of the reaction of 1 with carbon disulfide to 1,3-oxathiolene-2-thiones increases spectacularly on UV irradiation 67). We now wish to report some further photoreactions of 1 with various nucleophiles.
When a suspension of 1 in methanol was exposed to UV irradiation for several hours the ether 2 was formed in 65% yield. In ethanol-acetonitrile 1 gave the corresponding ethyl ether with 8% yield.
Whereas primary aliphatic amines react with 1 at room temperature to give aminophenols'), pyridine and its derivatives 3 are unreactive under these conditions. The latter, however, react with 1 photolytically to form the zwitterions 4.
Pyridinium phenolates, or phenol betaines, analogous to 4 have been prepared by the reaction of phenols, especially hydroquinone, with pyridine followed by deprotonation of the initially formed quaternary salts''. Photoreaction of 1 with pyridines is a kind of iodonium to pyridinium zwitterion conversion, i. e. a trans-ylidation. Similar trans-ylidations have been observed with a variety of iodonium ylides') but with the addition of catalysts and not photochemically.
Compounds 4 are fairly stable and decompose only at high temperatures. They are also inert towards strong nucleophiles, e. g. CH3O0. Their UV spectra are identical to that of the phenolate ion. Their mass spectra show peaks for the heterocyclic ring fragments. In one case, namely 4a, the molecular ion was also detected.
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## Abstract During crystallization of the pyridinium __N__‐phenolate dye 1 from a saturated aqueous solution of urea, 1‐(4‐hydroxyphenyl)‐2,4,6‐triphenylpyridinium cyanate (4) is formed unexpectedly as verified by IR, ^1^H‐NMR and X‐ray structural analysis. Such a course of reaction can be explaine
## Abstract Exclusive formation of 6‐aryloxy ethers **9** from an S~N~Ar reaction of methyl 2,6‐dichloronicotinate (**2**) with phenols **7** catalyzed by 1,4‐diazabicyclo[2.2.2]octane (DABCO) in the presence of stoichiometric triethylamine is described. The reaction proceeds __via__ the regioselec