| 1. |
- Janjetovic, Mario, et al.
(författare)
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Catalytic Iodination of the Aliphatic C-F Bond by YbI3(THF)(3): Mechanistic Insight and Synthetic Utility
- 2016
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Ingår i: Organic Letters. - : American Chemical Society (ACS). - 1523-7060 .- 1523-7052. ; 18:12, s. 2804-2807
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Tidskriftsartikel (refereegranskat)abstract
- A facile iodination protocol, of unactivated alkyl fluorides: using catalytic amounts of YbI3(THF)(3) in the presence of iodotrimethylsilane as a stoichiometric fluoride trapping agent is presented. H-1 NMR spectroscopy demonstrates a two-step :catalytic cycle where TMSI regenerates active YbI3(THF)(3). Finally, the catalytic reaction is extended a one-pot procdure to demonstrate a potential application of the method Overall, the findings present a distinct strategy for C-F bond transformations in the presence of catalytic YbI3(THF)(3).
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| 2. |
- Janjetovic, Mario
(författare)
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Lanthanide-mediated C-F Bond Activation Method Development and Mechanistic Investigation
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The use of transition-metals and main-group Lewis acids has proven to be an outstanding source for activation and subsequent functionalization of fluorinated compounds. However, the first is mainly limited to C(sp2)–F bonds which partially are activated by an adjacent heteroatom, and the latter is limited to simple C(sp3)–F bonds due to particularly strong Lewis acid character. The main focus of this thesis has been directed towards development of mild and chemoselective lanthanide mediated C–F bond activation of simple and functionalized alkyl fluorides from a synthetic point of view. The first part of the thesis covers a solvent dependent reductive HDF of alkyl fluorides by employing Sm(HMDS)2 as a single-electron transfer reagent. The Sm(II)-reagent, assisted by microwave heating, is capable of reductive cleavage of primary, secondary, and tertiary alkyl fluorides to the corresponding hydrocarbons in excellent yields The second part of the thesis describes the utilization of YbI3(THF)3 as a superior Lewis acid for the selective iodination of primary, secondary, and tertiary alkyl fluorides in presence of various common functional groups. The mechanism of the reaction was distinctively studied by the means of substrate reactivity, stereochemical analysis, and initial rate measurements. The reaction was further elaborated into a catalytic process in the presence of TMSI as a stoichiometric fluoride-trapping agent. 1H and 19F NMR spectroscopy demonstrated a two-step catalytic cycle where TMSI regenerates the active YbI3(THF)3. The third and final part of the thesis involves the development of a facile and efficient protocol of direct amination of alkyl fluorides employing La[N(SiMe3)2]3. The method was shown to tolerate various secondary nucleophilic amines as well as functionalized alkyl fluorides. A concerted transition state was proposed for the reaction based on 1H NMR spectroscopy, initial rate measurements, KIE, and steric effects. It was also found that La[N(SiMe3)2]3 promoted instantaneous and subsequent substitution of β-amino fluorides. 1H NMR spectroscopy revealed that the reaction appears to proceed via an aziridinium ion. Consequently, the reactive intermediate was prone to undergo ring-opening by various nucleophiles, yielding the corresponding β-substituted amines in high to excellent yields.
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| 3. |
- Janjetovic, Mario, et al.
(författare)
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Mild and Selective Activation and Substitution of Strong Aliphatic C-F Bonds
- 2015
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Ingår i: Chemistry-a European Journal. - : Wiley. - 0947-6539. ; 21:9, s. 3772-3777
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Tidskriftsartikel (refereegranskat)abstract
- A procedure for chemoselectively manipulating the strong aliphatic CF bond with direct transformation into a CN bond under mild conditions is reported. The activation and subsequent substitution of primary alkyl fluorides is mediated by La[N(SiMe3)(2)](3), and results in high to excellent yields of tertiary amines. The methodology displays high selectivity towards the C(sp(3))F bond, and a variety of secondary amines are applicable as nucleophiles. Mechanistic investigations reveal a reaction that is first order with respect to [La[N(SiMe3)(2)](3)], [(RRNH)-R-1-N-2], and [alkyl fluoride], and a 6-membered cyclic transition state is proposed. In addition, (HNMR)-H-1 spectroscopy shows that La[N(SiMe3)(2)](3) is the active species involved in the substitution and that protonolysis of the amine, yielding La[(NRR2)-R-1](3), lowers the reactivity.
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| 4. |
- Janjetovic, Mario, et al.
(författare)
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Solvent dependent reductive defluorination of aliphatic C-F bonds employing Sm(HMDS)(2)
- 2013
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 49:18, s. 1826-1828
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Tidskriftsartikel (refereegranskat)abstract
- Sm(HMDS)(2) in n-hexane mediates fast cleavage of primary, secondary and tertiary alkyl fluorides in good to excellent yields. In n-hexane Sm(HMDS)(2) exhibits uniquely enhanced reductive ability towards the C-F bond compared to when using THF as solvent.
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| 5. |
- Träff, Annika M., et al.
(författare)
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C-F bond substitution via aziridinium ion intermediates
- 2015
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 51:68, s. 13260-13263
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Tidskriftsartikel (refereegranskat)abstract
- Aliphatic 1,2-aminofluorides undergo extremely fast substitution reactions under the influence of lanthanum tris(hexamethyldisilazide). The substitution proceeds via an in situ generated aziridinium ion intermediate, which subsequently undergoes ring opening by addition of a nucleophile, yielding various beta-substituted amines.
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| 6. |
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