- Lewis-Base-Catalyzed Reductive Aldol Reaction to Access Quaternary Carbons
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A synthetic method for the efficient construction of β-hydroxylactones and lactams bearing α-quaternary carbon centers is described. This transformation relies on an electronically differentiated Lewis base catalyst, which is uniquely capable of promoting
- Deporre, Yvonne C.,Annand, James R.,Bar, Sukanta,Schindler, Corinna S.
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- Reaction of arylphosphines with singlet oxygen: intra- vs intermolecular oxidation.
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[reaction--see text] The chemistry of singlet oxygen with all three isomers of tris(methoxyphenyl)phosphine has been studied. For the severely hindered ortho isomer, intramolecular rearrangement to form phenyl diphenyl phosphinate is preferred to formatio
- Gao,Ho,Dong,Khuu,Franco,Sezer,Selke
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Read Online
- Flame retardant polycyanurate thermosets from the cyanate esters of triphenylphosphine oxide
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Three cyanate esters containing phosphorus are synthesized in good overall yields starting from bromoanisoles. Di- and tricyanates with meta configuration are most stable while para is less so. The para dicyanate ester isomer is particularly affected by water from the atmosphere. The meta dicyanate ester 2 has good thermal properties with glass transition at 268 °C and char yield of 65% in air at 600 °C. All three phosphorus-containing cyanate esters are low flammability in an open flame. They make highly combustible cyanate esters resins less flammable simply by blending. Mixing 10 wt% dicyanate ester 2 into bisphenol A or E dicyanate esters makes them rate V-0. Published 2018.? J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1100–1110.
- Davis, Matthew C.,Garrison, Michael D.,Ghiassi, Kamran B.,Groshens, Thomas J.,Redeker, Neil D.
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p. 1100 - 1110
(2018/03/21)
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- Aryl group - A leaving group in arylphosphine oxides
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The treatment of triphenylphosphine oxide with organometallic reagents leads to the substitution of up to three phenyl substituents with the incoming carbon nucleophile. The replacement of the phenyl/aryl group in tertiary diarylalkylphosphine oxides or even aryldialkylphosphine oxides was also observed. Naphthyl-substituted phosphine oxides undergo Michael-type addition at the naphthyl group when treated with organolithium reagent.
- Stankevi?, Marek,Pisklak, Jolanta,W?odarczyk, Katarzyna
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p. 810 - 824
(2016/01/20)
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- Mild and efficient oxidation of phosphorus(III) compounds with Selectfluor
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A novel and efficient oxidation of phosphorus(III) compounds with Selectfluor is described. The reactions smoothly led to the formation of tertiary phosphine oxides, phosphinates, and phosphonates in up to 99% yield under mild conditions in minutes.
- Chen, Qian,Zeng, Jiekun,Yan, Xinxing,Huang, Yulin,Du, Zhiyun,Zhang, Kun,Wen, Chunxiao
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supporting information
p. 3379 - 3381
(2016/07/11)
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- Lewis-acid-promoted stoichiometric and catalytic oxidations by manganese complexes having cross-bridged cyclam ligand: A comprehensive study
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Redox-inactive metal ions have been recognized to be able to participate in redox metal-ion-mediated biological and chemical oxidative events; however, their roles are still elusive. This work presents how the redox-inactive metal ions affect the oxidative reactivity of a well-investigated manganese(II) with its corresponding manganese(IV) complexes having cross-bridged cyclam ligand. In dry acetone, the presence of these metal ions can greatly accelerate stoichiometric oxidations of triphenylphosphine and sulfides by the manganese(IV) complexes through electron transfer or catalytic sulfoxidations by the corresponding manganese(II) complexes with PhIO. Significantly, the rate enhancements are highly Lewis-acid strength dependent on added metal ions. These metal ions like Al3+ can also promote the thermodynamic driving force of the MnIV-OH moiety to facilitate its hydrogen abstraction from ethylbenzene having a BDECH value of 85 kcal/mol, while it is experimentally limited to 80 kcal/mol for MnIV-OH alone. Adding Al3+ may also improve the manganese(II)-catalyzed olefin epoxidation with PhIO. However, compared with those in electron transfer, improvements in hydrogen abstraction and electron transfer are minor. The existence of the interaction between Lewis acid and the manganese(IV) species was evidenced by the blue shift of the characteristic absorbance of the manganese(IV) species from 554 to 537 nm and by converting its EPR signal at g = 2.01 into a hyperfine 6-line signal upon adding Al3+ (I = 5/2). Cyclic voltammograms of the manganese(IV) complexes reveal that adding Lewis acid would substantially shift its potential to the positive direction, thus enhancing its oxidizing capability.
- Dong, Lei,Wang, Yujuan,Lv, Yanzong,Chen, Zhuqi,Mei, Fuming,Xiong, Hui,Yin, Guochuan
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p. 5418 - 5427
(2013/06/26)
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- Iron porphyrin-catalyzed olefination of ketenes with diazoacetate for the enantioselective synthesis of allenes
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In the presence of Ph3P and catalytic Fe(TCP)Cl, ketenes could react with EDA to give allenes in high yields under neutral conditions for the first time. By employing chiral phosphine instead of PPh3, allenes could be synthesized with high enantioselectivity (93-98% ee) in good yields. Copyright
- Li, Chuan-Ying,Wang, Xiao-Bing,Sun, Xiu-Li,Tang, Yong,Zheng, Jun-Cheng,Xu, Zheng-Hu,Zhou, Yong-Gui,Dai, Li-Xin
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p. 1494 - 1495
(2007/10/03)
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- Synthesis of a family of triarylphosphanes with fluorous phase affinity
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A very efficient synthesis of new perfluoro-functionalized triarylphosphanes using an oxygen substituent as the branching point for the introduction of the perfluoro chain has been developed. This approach enabled the introduction of the perfluoro tail at the para, meta, and oitho position, giving highly perfluorinated analogues of triphenylphosphane con-taining between 54 and 59 wt% fluorine. This methodology has been extended to the synthesis of a perfluoro analogue of l,2-bis(diphenylphosphanyl)ethane. Fluorous/organic partition coefficients of some of the perfluorophosphanes have been measured, as well as their rates of oxidation. WILEY-VCH Verlag GmbH, 2002.
- Sinou, Denis,Maillard, David,Pozzi, Gianluca
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p. 269 - 275
(2007/10/03)
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