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81.
Cobley CJ Gardner K Klosin J Praquin C Hill C Whiteker GT Zanotti-Gerosa A Petersen JL Abboud KA 《The Journal of organic chemistry》2004,69(12):4031-4040
A series of mono- and bidentate phosphites was prepared with (S)-5,5',6,6'-tetramethyl-3,3'-di-tert-butyl-1,1'-biphenyl-2,2'-dioxy [(S)-BIPHEN] as a chiral auxiliary and screened in the asymmetric hydroformylation of allyl cyanide. These hydroformylation results were compared with those of two existing chiral ligands, Chiraphite and BINAPHOS, whose utility in asymmetric hydroformylation has been previously demonstrated. Bisphosphite 11 with a 2,2'-biphenol bridge was found to be the best overall ligand for asymmetric hydroformylation of allyl cyanide with up to 80% ee and regioselectivities (branch-to-linear ratio, b/l) of 20 with turnover frequency of 625 [h(-)(1)] at 35 degrees C. BINAPHOS gave enantioselectivities up to 77% ee when the reaction was conducted in either acetone or neat but with poor regioselectivity (b/l 2.8) and activities 7 times lower than that of 11. The product of allyl cyanide hydroformylation using (R,R)-11 was subsequently transformed into (R)-2-methyl-4-aminobutanol, a useful chiral building block. Single-crystal X-ray structures of (S,S)-11 and its rhodium complex 19 were determined. 相似文献
82.
The synthesis and characterization of both diastereomers of a system comprised of two [2.2]paracyclophane units linked through a single 4,4' bond are described. Both the meso and d,l diastereomers of 4,4'-bis(octafluoro[2.2]paracyclophane) have been prepared via a palladium-catalyzed reductive homocoupling reaction by copper, producing a 3:2 ratio of meso and d,l diastereomers. A similar reductive homocoupling of pseudo-o-iodotrifluoromethyloctafluoro[2.2]paracyclophane gave only the analogous meso diastereomer. Single-crystal X-ray structures were obtained for all of the diparacyclophane products. 相似文献
83.
The presence of catalytic amounts of CeCl(3) improves yields and simplifies procedure in the Reformatsky reactions of ethyl bromofluoroacetate with aldehydes and ketones to generate diastereomeric mixtures of alpha-fluoro-beta-hydroxy esters, some of which can be separated by crystallization or column flash chromatography. Diastereomerically pure alpha-fluoro-beta-hydroxy acids are obtained by mild alkaline hydrolysis of the resolved alpha-fluoro-beta-hydroxy esters. Detailed NMR data of new alpha-fluoro-beta-hydroxy esters and alpha-fluoro-beta-hydroxy acids are also presented. 相似文献
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Annaliese E. Thuijs George Christou Khalil A. Abboud 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(3):185-187
The title dodecanuclear Mn complex, namely dodeca‐μ2‐acetato‐κ24O:O′‐tetraaquatetra‐μ2‐nitrato‐κ8O:O′‐tetra‐μ4‐oxido‐octa‐μ3‐oxido‐tetramanganese(IV)octamanganese(III) nitromethane tetrasolvate, [Mn12(CH3COO)12(NO3)4O12(H2O)4]·4CH3NO2, was synthesized by the reaction of Mn2+ and Ce4+ sources in nitromethane with an excess of acetic acid. This compound is distinct from the previously known single‐molecule magnet [Mn12O12(O2CMe)16(H2O)4], synthesized by Lis [Acta Cryst. (1980), B 36 , 2042–2044]. It is the first Mn12‐type molecule containing nitrate ligands to be directly synthesized without the use of a preformed cluster. Additionally, this molecule is distinct from all other known Mn12 complexes due to intermolecular hydrogen bonds between the nitrate and water ligands, which give rise to a three‐dimensional network. The complex is compared to other known Mn12 molecules in terms of its structural parameters and symmetry. 相似文献