- Photochemical generation of six- and five-membered cyclic vinyl cations
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The photochemical solvolyses of 4-tert-butylcyclohex-1-enyl(phenyl)iodonium tetrafluoroborate (1) and cyclopent-1-enyl(phenyl)iodonium tetrafluoroborate (2) in methanol yield vinylic ethers and vinylic cycloalkenyliodobenzenes and cycloalkenylbenzene, which are the trapping products of the geometrically destabilized C6-ring and C5-ring vinyl cation with the solvent and with the leaving group iodobenzene. Iodonium salt 2 also yields an allylic ether and allylic cyclopentenyliodobenzenes and cyclopentenyl-benzene, which are the trapping products of the C5-ring allylic cation produced from the C5-ring vinyl cation by a hydride shift in a typical carbocationic rearrangement.
- Slegt, Micha,Gronheid, Roel,Van Vlugt, Dennis Der,Ochiai, Masahito,Okuyama, Tadashi,Zuilhof, Han,Overkleeft, Hermen S.,Lodder, Gerrit
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p. 2227 - 2235
(2007/10/03)
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- Michael addition-elimination mechanism for nucleophilic substitution reaction of cycloalkenyl iodonium salts and selectivity of 1,2-hydrogen shift in cycloalkylidene intermediate
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(Chemical Equation Presented) Reactions of cyclohexenyl and cyclopentenyl iodonium salts with cyanide ion in chloroform give cyanide substitution products of allylic and vinylic forms. Deuterium-labeling experiments show that the allylic product is formed via the Michael addition of cyanide to the vinylic iodonium salt, followed by elimination of the iodonio group and 1,2-hydrogen shift in the 2-cyanocycloalkylidene intermediate. The hydrogen shift preferentially occurs from the methylene rather than the methine β-position of the carbene, and the selectivity is rationalized by the DFT calculations. The Michael reaction was also observed in the reaction of cyclopentenyliodonium salt with acetate ion in chloroform. The vinylic substitution products are ascribed to the ligand-coupling (via λ3-iodane) and elimination-addition (via cyclohexyne) pathways.
- Fujita, Morifumi,Wan, Hyeok Kim,Fujiwara, Koji,Okuyama, Tadashi
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p. 480 - 488
(2007/10/03)
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- Chromium(ii)-mediated reactions of iodonium tetrafluoroborates with aldehydes: Umpolung of reactivity of diaryl-, alkenyl(aryl)-, and alkynyl(aryl)iodonium tetrafluoroborates
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The method described herein allows us, for the first time, to perform umpolung of reactivity of diaryl-, alkenyl(aryl)-, and alkynyl(aryl)iodonium tetrafluoroborates. The method involves generation of organochromium(III) species via reaction of iodonium salts with anhydrous chromium dichloride, followed by their nucleophilic addition to aldehydes to yield alcohols. In contrast to the reaction of aryl and alkenyl halides with chromium dichloride, these iodonium salts are so active that organochromium(III) could be generated without using a nickel catalyst. Substituent effects of unsymmetrically substituted diaryliodonium salts on the product profiles are in good agreement with the reported mode of decomposition of the intermediate unsymmetrical diaryliodanyl radicals. Alkenyl(mesityl)iodonium tetrafluoroborates undergo exclusive alkenylation of aldehydes with no signs of the formation of an arylation product.
- Chen, Da-Wei,Ochiai, Masahito
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p. 6804 - 6814
(2007/10/03)
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- Studies on the Synthesis of Heterocyclic Compounds. XVI. Cleavage of 1,3-Benzodioxoles and -Benzoxathioles by Sodium Iodide-Acyl Chloride
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The cleavage reaction of ethereal and thioethereal bonds with sodium iodide and acyl chloride has been studied.In all the 1,3-benzodioxoles and -benzoxathioles studied, the opening of the heterocyclic ring with formation of 1,2-diacetoxybenzene or 2-hydroxythiophenol diacetic acid ester and gem-diiodoalkanes and iodoalkenes has been observed.The structure of newly prepared compounds has been determined by analytical and spectroscopic data or comparison with authentic samples.
- Corda, Luciana,Fadda, Anna Maria,Maccioni, Antonio,Maccioni, Anna Maria,Podda, Gianni
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p. 311 - 314
(2007/10/02)
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