7333-65-5Relevant articles and documents
One-Step Synthesis of Triphenylphosphonium Salts from (Het)arylmethyl Alcohols
Abaev, Vladimir T.,Chalikidi, Petrakis N.,Demidov, Oleg P.,Gutnov, Andrey V.,Magkoev, Taimuraz T.,Trushkov, Igor V.,Uchuskin, Maxim G.
, p. 9838 - 9846 (2021/07/28)
Two approaches for the synthesis of substituted phosphonium salts from easily available benzyl alcohols and their heterocyclic analogs have been developed. The developed protocols are complementary: the direct mixing of alcohol, trimethylsilyl bromide, and triphenylphosphine in 1,4-dioxane followed by heating at 80 °C was found to be more efficient for acid-sensitive substrates, such as salicyl or furfuryl alcohols as well as secondary benzyl alcohols, while a one-pot procedure including sequential addition of trimethylsilyl bromide and triphenylphosphine gave higher yields for benzyl alcohols bearing electroneutral or electron-withdrawing substituents.
Ion-pairing of phosphonium salts in solution: C-H...halogen and C-H...π hydrogen bonds
Ammer, Johannes,Nolte, Christoph,Karaghiosoff, Konstantin,Thallmair, Sebastian,Mayer, Peter,Devivie-Riedle, Regina,Mayr, Herbert
supporting information, p. 14612 - 14630 (2013/11/06)
The 1HNMR chemical shifts of the C(α)-H protons of arylmethyl triphenylphosphonium ions in CD2Cl2 solution strongly depend on the counteranions X-. The values for the benzhydryl derivatives Ph2CH-PPh3+ X -, for example, range from δH=8.25 (X -=Cl-) over 6.23 (X-=BF4 -) to 5.72ppm (X-=BPh4-). Similar, albeit weaker, counterion-induced shifts are observed for the ortho-protons of all aryl groups. Concentration-dependent NMR studies show that the large shifts result from the deshielding of the protons by the anions, which decreases in the order Cl- > Br- a‰ BF4 - > SbF6-. For the less bulky derivatives PhCH2-PPh3+ X-, we also find C-H...Ph interactions between C(α)-H and a phenyl group of the BPh4- anion, which result in upfield NMR chemical shifts of the C(α)-H protons. These interactions could also be observed in crystals of (p-CF3-C6H4)CH2-PPh 3+ BPh4-. However, the dominant effects causing the counterion-induced shifts in the NMR spectra are the C-H...X- hydrogen bonds between the phosphonium ion and anions, in particular Cl- or Br-. This observation contradicts earlier interpretations which assigned these shifts predominantly to the ring current of the BPh4- anions. The concentration dependence of the 1HNMR chemical shifts allowed us to determine the dissociation constants of the phosphonium salts in CD2Cl2 solution. The cation-anion interactions increase with the acidity of the C(α)-H protons and the basicity of the anion. The existence of C-H...X- hydrogen bonds between the cations and anions is confirmed by quantum chemical calculations of the ion pair structures, as well as by X-ray analyses of the crystals. The IR spectra of the Cl- and Br- salts in CD2Cl2 solution show strong red-shifts of the C-H stretch bands. The C-H stretch bands of the tetrafluoroborate salt PhCH 2-PPh3+ BF4- in CD 2Cl2, however, show a blue-shift compared to the corresponding BPh4- salt.
Dirhodium(II)-catalyzed intramolecular C-H amination of aryl azides
Shen, Meihua,Leslie, Brooke E.,Driver, Tom G.
supporting information; experimental part, p. 5056 - 5059 (2009/03/11)
(Chemical Equation Presented) Azides to indoles: Dirhodium(II)-catalyzed decomposition of aryl azides was developed as a mild, functional group tolerant method for the synthesis of indoles (see scheme).
