85685-99-0Relevant articles and documents
Diastereoselective Rhodium Catalyzed [4 + 2] Cycloisomerization of Allenes
Li, Jun,Gilbertson, Scott R.
supporting information, p. 2911 - 2914 (2021/05/05)
A diastereoselective [4 + 2] cycloisomerization of asymmetric allenyl dienes is reported. The asymmetric dienyl allenes are synthesized using the method reported by Ma. These substrates readily undergo diastereoselective intramolecular rhodium catalyzed [4 + 2] cycloisomerization analogous to thermal intramolecular Diels-Alder reactions. Overall, 29 examples are presented with tethers possessing nitrogen, oxygen, and carbon. Diastereoselectivities range from 99:1 to 90:10 in most examples.
31P NMR spectroscopic analysis on photooxidation of 1,n-bis(diphenylphosphino)alkanes with the aid of DFT calculations
Yasui, Shinro,Yamazaki, Shoko
, (2020/02/15)
The chloroform-d solution of diphosphine, 1,n-bis(diphenylphosphino)alkane (Ph2P(CH2)nPPh2; n = 1-6), was photolyzed with light from a xenon lamp in air. The progress of the reaction was followed by 31P NMR spectroscopy. The observed spectral change showed that the diphosphine is initially oxidized to diphosphine monoxide, Ph2P(═O)(CH2)nPPh2, which is further oxidized to diphosphine dioxide, Ph2P(═O)(CH2)nP(═O)Ph2. The oxidation of the diphosphine to the diphosphine monoxide took place according to first-order kinetics with respect to the concentration of the diphosphine, the first-order rate constant, kobs, being larger with increasing number of the methylene units in the spacer. The observation in kinetics is interpreted based on the conformation of the diphosphine radical cation intermediate initially generated by electron transfer from the photoexcited diphosphine to oxygen. Density functional theory (DFT) calculations predict that the diphosphine radical cation takes “folded” conformation where two phosphorus atoms are arranged closely to each other. The “folded” conformer of the diphosphine radical cation results from electrostatic interaction of these two phosphorus atoms. This conformer explains the observed dependency of kobs on the length of the spacer in the diphosphine.
Intramolecular stabilization of the phosphine radical cation by the second phosphorus atom during the photooxidation of diphosphines:31P NMR spectroscopic analysis
Yasui, Shinro,Yamazaki, Shoko
, p. 422 - 424 (2015/05/27)
Diphosphines, Ph2P(CH2)nPPh2 1 (n = 1, 2, 3, 4, and 6), were photolyzed by a xenon lamp in air. The 31P NMR spectroscopic analysis of the reaction showed that 1 is oxidized, according to first-order kinetics, to the monoxide, which is further oxidized to the dioxide. The dependence of the rate constants for the first oxidation on the chain-length n in 1 is interpreted in terms of the orientation of the p-orbitals on the two phosphorus atoms in the intermediate, the diphosphine radical cation.
Selective mono reduction of bis-phosphine oxides under mild conditions
Petersson, Maria J.,Loughlin, Wendy A.,Jenkins, Ian D.
experimental part, p. 4493 - 4494 (2009/05/06)
Bis-phosphine oxides can be selectively reduced to bis-phosphine monoxides under exceptionally mild conditions using triflic anhydride and a thiol. The Royal Society of Chemistry.
