- Preparation of (perfluoroalkyl)alkane thiols via Zemplén deacylation of fluorous (perfluoroalkyl)alkyl thioacetates
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Convenient and robust synthesis of (perfluoroalkyl)alkane thiols [(CnF2n+1(CH2)mSH); m/n = 3/4,6,8,10, 4a-d; m/n = 2/6, 8; m/n = 1/1,2,3,7,8H, 12a-e] was developed starting from commercially available fluorous alcohols (1a-d, 5, 9a-e). The intermediate (perfluoroalkyl)alkyl iodides and/or sulfonates were reacted with potassium thioacetate in DMF, and the resulting thioacetates were deacetylated by a Zemplén analogue reaction. The (perfluoroalkyl)alkane thiols were obtained in good overall yields and high purity.
- Menczinger, Bálint,Nemes, Anikó,Szíjjártó, Csongor,Rábai, József
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- A fluorous ethylenediamine promoted direct C-H arylation of unactivated arenes with aryl halides
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A novel and recyclable fluorous ethylenediamine was prepared. Together with potassium tert-butoxide, the fluorous ethylenediamine showed a good activity in promoting the coupling of aryl halides with benzene derivatives without the aid of transition-metal catalysts. Furthermore, a chain homolytic aromatic substitution mechanism was proposed in this paper.
- Zhu, Yi-Wei,Shi, Yi-Xin
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- Fluorous dimethylthiocarbamate (FDMTC) protecting groups for alcohols
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N,N-Bis(perfluoroalkyl)thiocarbamoyl chlorides (FDMTC-Cls) were synthesized as reagent for the protection of alcohols. Using the crystalline FDMTC-Cls, the FDMTC groups were introduced into the alcohol molecules in excellent yields in the presence of sodium hydride in THF at room temperature. The products were separated from the excess alcohols by solid-phase extraction with a fluorous reverse-phase silica gel column (Fluorous Solid Phase Extraction; FSPE). The FDMTC groups were readily removed by oxidation with m-chloroperbenzoic acid (m-CPBA) and subsequent hydrolysis with KHCO3.
- Kojima, Masaru,Nakamura, Yutaka,Ishikawa, Takuma,Takeuchi, Seiji
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p. 6309 - 6314
(2007/10/03)
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- Effect of a Perfluoroalkyl Group on the Elimination and Substitution Reactions of Two Homologous Series of Perfluoroalkyl-Substituted Iodoalkanes
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Substitution and elimination reactions of two homologous series of compounds, induced by strong bases, were studied in aqueous alcohol and anhydrous methanol solution.Series I compounds, RF(CH2)nI having n = 2 (RF = a perfluoroalkyl group, also named an F-alkyl group), gave only RFCH=CH2 under all conditions.By contrast, RF(CH2)3Igave 4-10 times as much substitution as elimination products.Isomerization of RFCH2CH=CH2 (6) to RFCH=CHCH3 (7) occurred; this result may account, in part, for the extremely high 7/6 alkene ratios (37-81/1) obtained from elimination reactions of RFCH2CHICH3.All series II compounds, RFCH2CHI(CH2) nCH3 (n = 0-5), gave entirely elimination, and principally toward the RF group.E/Z isomer ratios varied from 2.65 to 5.These results were compared to those obtained from 1- and 2-iodooctane under the same conditions.A practical synthesis of CF3(CF2)5CH2CH2CH2I is described; the isomeric (F-alkyl)propenes 6 and 7 were also separately prepared.Rates of reactions under standard conditions for both series I and II compounds were measured.Kinetically, only second-order processes were observed, but a sharp break occurred in rate as the RF group was separated more than two carbons from the departing iodine atom, in series I compounds.Series II compounds reacted about one-tenth as fast as series I compounds.These results are discussed in the context of previous work with F-alkyl-substituted compounds.
- Brace, Neal O.,Marshall, Lawrence W.,Pinson, Carol J.,Wingerden, Gail van
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p. 2361 - 2368
(2007/10/02)
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