- Osmium-Promoted Transformation of Alkyl Nitriles to Secondary Aliphatic Amines: Scope and Mechanism
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The transformation of alkyl nitriles to symmetrical and asymmetrical secondary aliphatic amines promoted by the hexahydride complex OsH6(PiPr3)2 (1) is described, and the mechanisms of the reactions involved are established. Complex 1 catalyzes the aforementioned transformations of aryl-, pyridyl-, and alkoxy-functionalized alkyl nitriles with linear or branched chains. The formation of the secondary amines involves primary imines, primary amines, and secondary imines as organic intermediates. The reactions take place under mild conditions (toluene, 100 °C, and 4 bar of H2). Stoichiometric reactions of 1 with pivalonitrile and 2-methoxyacetonitrile have allowed us to isolate the trihydride azavinylidene derivatives OsH3{═N═CHR}(PiPr3)2 (R = tBu (3), CH2OMe (4)). Their formation involves the insertion of the N-C triple bond of the substrates into an Os-H bond of the unsaturated tetrahydride OsH4(PiPr3)2 (A), which is generated by reductive elimination of H2 from the hexahydride precursor. The reaction of these trihydride azavinylidene species with H2 is the key step for the reduction of the N-C triple bond of the nitriles. In the absence of H2, the attack of A to the azavinylidene ligand produces the rupture of its C(sp2)-C(sp3) bond. As a consequence of this attack and the presence of primary imines and amines in the reaction media, the binuclear complexes (PiPr3)2H4Os(μ-CN)OsH3{κ1-N-(NH═CHCH2OMe)}(PiPr3)2 (5) and (PiPr3)2H4Os(μ-CN)OsH3{κ1-N-(NH2CH2CH2OMe)}(PiPr3)2 (6) have been isolated and characterized by X-ray diffraction analysis, for 2-methoxyacetonitrile. DFT calculations reveal noticeable similarities between the hydrogenations of nitriles to primary imines and those of primary imines to primary amines.
- Babón, Juan C.,Esteruelas, Miguel A.,López, Ana M.,O?ate, Enrique
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supporting information
p. 2177 - 2188
(2020/06/08)
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- Synthesis and evaluation of oryzalin analogs against Toxoplasma gondii
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The synthesis and evaluation of 20 dinitroanilines and related compounds against the obligate intracellular parasite Toxoplasma gondii is reported. Using in vitro cultures of parasites in human fibroblasts, we determined that most of these compounds selectively disrupted Toxoplasma microtubules, and several displayed sub-micromolar potency against the parasite. The most potent compound was N1,N1-dipropyl-2,6-dinitro-4-(trifluoromethyl)-1,3- benzenediamine (18b), which displayed an IC50 value of 36 nM against intracellular T. gondii. Based on these data and another recent report [Ma, C.; Tran, J.; Gu, F.; Ochoa, R.; Li, C.; Sept, D.; Werbovetz, K.; Morrissette, N. Antimicrob. Agents Chemother. 2010, 54, 1453], an antimitotic structure-activity relationship for dinitroanilines versus Toxoplasma is presented.
- Endeshaw, Molla M.,Li, Catherine,Leon, Jessica De,Yao, Ni,Latibeaudiere, Kirk,Premalatha, Kokku,Morrissette, Naomi,Werbovetz, Karl A.
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scheme or table
p. 5179 - 5183
(2010/10/03)
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- A study of the complexation of bis(m-phenylene) crown ethers and secondary ammonium ions
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Two macrocycles, bis(m-phenylene)-26-crown-8 (1) and bis(m-phenylene)-32-crown-10 (2), were combined with several linear components, dibenzyl- (3·PF6), di-n-butyl- (4·PFe), and diphenethyl(5·PF6) ammonium hexafluorophosphate salts. The smaller macrocycle 1 was shown not to complex effectively with any of the ammonium salts in solution by 1H NMR, but 1:1 complexes were shown to exist in the "gas phase" as [1:3], [1:4], and [1:5] by high-resolution fast atom bombardment mass spectrometry (HRFABMS) and electrospray ionization mass spectrometry (ESIMS). The X-ray crystal structure of macrocycle 1 is reported. The larger macrocycle 2 did form 1:2 complexes with the ammonium salts in solution, which were observed as well in the solid and gas phases. X-ray crystal structures of the pseudorotaxanes [2:(3)2]·2PF6 and [2:(5)2]·2PF6 were determined and are discussed. The pseudorotaxanes are stabilized by hydrogen bonding between the ammonium hydrogens of the linear salt unit and the oxygens of the crown ether macrocycle. Secondary stabilization also occurs by edge-to-face π stacking.
- Bryant, William S.,Guzei, Ilia A.,Rheingold, Arnold L.,Merola, Joseph S.,Gibson, Harry W.
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p. 7634 - 7639
(2007/10/03)
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