- Oxidation chemistry of perfluoroalkyl-segmented thiols, disulfides, thiosulfinates and thiosulfonates: The role of the perfluoroalkyl group in searching out new chemistry
-
The oxidation chemistry of perfluoroalkyl-segmented thiols, RF-R-SH (1), thiosulfinates, RF-R-S(O)S-R-RF (3), thiosulfonates, RF-R-S(O2)S-R-RF (4) and disulfides, RF-R-SS-R-RF (5) (in which RF=n-C6F13 or n-C8F17 and R=CH2CH2) is studied herein. Base catalyzed reaction of C6 thiol 1 with hydrogen peroxide gives pure disulfide 5, quantitatively. Other, less suitable methods for the oxidation of thiol 1 are also examined and compared. Selective oxidation of disulfide 5 by peroxy acids in chlorinated solvents gives excellent yields of thiosulfinate 3. Unlike their hydrocarbon analogues, which are unstable to heating or storage, the RF-segmented thiosulfinates 3 are relatively stable, crystalline compounds. Selective oxidation of 3 by sodium metaperiodate gives thiosulfonate 4 in high yield. Side reactions intervene with unfavorable conditions, or when peroxy acetic acid in acetic acid is used as oxidant,. Oxidation of 5 by hydrogen peroxide in low conversion gives 4 and two new compounds, 8 and 9. Compound 8 is n-C6F13S(O)2CH2CH2C 6F13 (probably the sulfinate ester and not the sulfone), and 9 is most likely the O,S-sulfenyl sulfinate or, possibly an isomer, the vic-disulfoxide. A free radical chain mechanism is proposed for conversion of 4 (or 9) to 8. Compounds 8 and 9 are stable in solution and are identified by MS/GC. In 3, 4 and 5, the ν CH bands correlate with NMR of CH2 at C(1) and C(2) positions, both 1H and 13C NMR. The RF-segment in these unique sulfur compounds enhances their utility and modifies their chemical and physical properties in important and interesting ways.
- Brace, Neal O.
-
-
Read Online
- A Sm(II)-mediated cascade approach to dibenzoindolo[3,2- b ]carbazoles: Synthesis and evaluation
-
Previously unstudied dibenzoindolo[3,2-b]carbazoles have been prepared by two-directional, phase tag-assisted synthesis utilizing a connective-Pummerer cyclization and a SmI2-mediated tag cleavage-cyclization cascade. The use of a phase tag allows us to exploit unstable intermediates that would otherwise need to be avoided. The novel materials were characterized by X-ray, cyclic voltammetry, UV-vis spectroscopy, TGA, and DSC. Preliminary studies on the performance of OFET devices are also described.
- Levick, Matthew T.,Grace, Iain,Dai, Sheng-Yao,Kasch, Nicholas,Muryn, Christopher,Lambert, Colin,Turner, Michael L.,Procter, David J.
-
supporting information
p. 2292 - 2295
(2014/05/06)
-
- Exploiting Sm(ii) and Sm(iii) in SmI2-initiated reaction cascades: Application in a tag removal-cyclisation approach to spirooxindole scaffolds
-
A tag removal-cyclisation sequence is described that is initiated by reduction using a Sm(ii) species and completed by a Sm(iii) Lewis acid that is formed in an earlier stage. Therefore, the reaction cascade utilises both oxidation states of a samarium reagent in discrete steps and allows access to privileged, pyrrolidinyl-spirooxindole scaffolds and analogues inspired by the anti-cancer natural product spirotryprostatin A. The Royal Society of Chemistry 2011.
- Coote, Susannah C.,Quenum, Seidjolo,Procter, David J.
-
p. 5104 - 5108
(2011/08/07)
-
- Preparation, reactions and physical properties of segmented 2-(perfluoroalkyl)ethanesulfinic acids and their derivatives. the role of the perfluoroalkyl group in finding new and useful compounds and in searching out new chemistry
-
2-(Perfluoroalkyl)ethanesulfinic acids of the formula RFCH2CH2SO2H (2, where RF=n-C6F13, or n-C8F17) are synthesized from the thiol, RFCH2CH2SH (1). These segmented acids 2 have sharp melting point (mp) and can be recrystallized. The C6 or C8 perfluoroalkyl group confers unusual "fluophilic" properties to acids 2 and their derivatives. Water solutions of acids 2 and their Na, K, Cs and Bu4N salts are highly surface active and stable for several days, and are more effective in reducing surface tension at the air/water interface than sodium n-perfluorooctanesulfonate (10). Sodium salts 2 (C6, C8) are converted to K and Cs salts by methathesis in high yield. However, the amphiphilic Bu4N salts of 2 (C6, C8) are best prepared in a biphasic system (C6, 99.6% yield). Acids 2 are synthesized by three methods. (1) Oxidation of the C8 thiol 1 (at -35°C) by m-CPBA gives acid 2 (C8) in 73% yield and unwanted disulfide (3) in 27% yield. The bulky, strongly electronegative RF group of 1 may slow oxidation of the RSOH (intermediate) to allow disproportionation with RSH into disulfide 3 and water. (2) Hydrolysis of RFCH2CH2SO2SCH2CH 2RF (4) with strong base gives salt 2 (C6, or C8; 92% yield). (3) Heating sulfone, RFCH2CH2SO2CH2CH 2Y (8) with a base (M2CO3) eliminates RFCH2CH2SO2M (2, M=Na, K, Cs) in 95-100% yield (C6, C8). Alternatively, 8 with the sodium thiolate of 1 gives RFCnH2nSCH2CH2Y (7, 90%) and sodium salt 2 (C6, 95%). Conjugate addition of the RFCH2CH2SO2- to CH2CHY gives sulfones 8, and RFCH2CH2SO2- adds stereospecifically to cyclohexene oxide, giving the trans-adduct 13. RFCH2CH2SO2H (2), with azo initiator, telomerizes acrylamide to a water-soluble, surface active product.
- Brace, Neal O.
-
-
- Synthesis of terminally perfluorinated long-chain alkanethiols, sulfides and disulfides from the corresponding halides
-
Semifluorinated n-alkanethiols, symmetrical sulfides and disulfides bearing the chain(s) F(CF2)n(CH2)m with n=4, 6, 8, 10, and m=2, 11 have been prepared by various synthetic methods, starting from the corresponding iodides or bromides. Methods based on sodium hydrogen sulfide, commonly used to accomplish this conversion, treatment of the Bunte salt obtained from sodium thiosulfate, the basic hydrolysis of isothiouronium salts, the hydrolysis under mild conditions of thiophosphorates formed from sodium thiophosphate and the basic hydrolysis of thiol acetic acid derivatives, have been investigated and compared relatively to the selective synthesis of the title compounds. The thiolacetic route yields essentially the thiols with some amounts of disulfides. Results from thiourea appears similar. Sodium thiophosphate constitutes an excellent route for the synthesis of thioethers, particularly when starting from the bromides. The two classical methods based on sodium hydrogen sulfide and sodium thiosulfate exhibit poor selectivity. It has been possible to obtain all the sulfur compounds reported in the pure state.
- Naud,Calas,Blancou,Commeyras
-
p. 173 - 183
(2007/10/03)
-
- Phase transfer synthesis of symmetrical di-terminally perfluorinated alkyl trithiocarbonates
-
Symmetrical di-terminally perfluorinated alkyl trithiocarbonates having the formula [F(CF2)n(CH2)mS]2CS (n = 4,6,8 m = 2 and n = 6,8 m = 11) were prepared in good yield under phase-transfer catalytic conditions starting from perfluoroalkyl alkyl iodides F(CF2)n(CH2)mI.
- Naud,Calas,Blancou,Commeyras
-
-