- Dynamic kinetic resolution of 1-substituted-3-methyl-3-phospholene oxides via the formation of diastereomeric alkoxyphospholenium salts
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A dynamic kinetic resolution method based on the formation of covalent diastereomeric intermediates was elaborated for the preparation of enantiomerically enriched 1-substituted-3-methyl-3-phospholene oxides. The 3-phospholene oxides were first converted to the corresponding chloro-3-phospholenium chlorides. The dynamic interconversion between the enantiomers of the chlorophospholenium salts was verified experimentally, as it is the key step for a dynamic resolution. The cyclic chlorophospholenium salts were reacted with a chiral auxiliary bearing a hydroxy function to form the corresponding diastereomeric alkoxyphospholenium salts in unequal amounts. The diastereomeric species then rearranged into the corresponding optically active 3-phospholene oxides upon heating. After a screening of chiral auxiliaries and the optimization of the reaction conditions, several scalemic 1-aryl- or 1-alkyl-3-methyl-3-phospholene oxides were prepared in excellent yields and with ee-s up to 35%. The key steps of this resolution were investigated by quantum chemical calculations to get some insights into the factors responsible for the stereoselection.
- Bagi, Péter,Herbay, Réka,ábrányi-Balogh, Péter,Mátrav?lgyi, Béla,Fogassy, Elemér,Keglevich, Gy?rgy
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p. 5850 - 5857
(2018/08/29)
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- General Approaches to Phosphinidenes via Retroadditions
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The retroaddition strategy for the generation of phosphinidenes involves thermal and photochemical decomposition of 1-arylphosphiranes and photolysis of 1-aryl-3-phospholenes.Evidence that free phosphinidenes are produced as reactive intermediates includes a lack of dependence of the conversion rate on precursor and substrate concentrations and the nature of the reaction products.These are best rationalized by the addition of phosphinidenes to carbon-carbon ?-bonds forming three-membered rings and the dimerization of phosphinidenes to diphosphenes.
- Li, Xinhua,Lei, Deqing,Chiang, Michael Y.,Gaspar, Peter P.
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p. 8526 - 8531
(2007/10/02)
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- REACTION OF PHOSPHOLES WITH ACIDS; PROTON SHIFTS IN 1H-λ5-PHOSPHOLES
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Addition to phospholes of gaseous HCl at -90 deg C or of an excess of trifluoromethanesulphonic acid at -70 deg C, results in P-protonation.The triflate solutions are stable up to room temperature, but the 1H-phospholium chlorides form PV adducts at -70 deg C, which rapidly rearrange by a sigmatropic H-shift.The observed product is a 1-chloro-2,5-dihydrophospholium chloride.Addition of a chloride ion source to the triflates produces the same result.Unprotonated 3,4-dimethyl-1-phenyl phosphole was found to react at a double bond of its 1H-phospholium ion, forming a crystalline 1,3'-biphospholium dimer.
- Quin, Louis D.,Belmont, Stephen E.,Mathey, Francois,Charrier, Claude
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p. 629 - 634
(2007/10/02)
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