An aza analogue of the Rubottom oxidation is reported. This facile transformation takes place at ambient temperature and directly converts silyl enol ethers to the corresponding primary ...α-aminoketones. The use of hexafluoroisopropanol (HFIP) as the solvent is essential for the success of this reaction. Overall this process is well-suited for the aza-functionalization and derivatization of complex organic molecules.
Herein we disclose a scalable organocatalytic direct arylation approach for the regio- and atroposelective synthesis of non-C 2-symmetric 2,2′-dihydroxy-1,1′-binaphthalenes (BINOLs). In the presence ...of catalytic amounts of axially chiral phosphoric acids, phenols and naphthols are coupled with iminoquinones via a cascade process that involves sequential aminal formation, sigmatropic rearrangement, and rearomatization to afford enantiomerically enriched BINOL derivatives in good to excellent yields. Our studies suggest that the (local) symmetry of the initially formed aminal intermediate has a dramatic impact on the level of enantioinduction in the final product. Aminals with a plane of symmetry give rise to BINOL derivatives with significantly lower enantiomeric excess than unsymmetrical ones featuring a stereogenic center. Presumably asymmetric induction in the sigmatropic rearrangement step is significantly more challenging than during aminal formation. Sigmatropic rearrangement of the enantiomerically enriched aminal and subsequent rearomatization transfers the central chirality into axial chirality with high fidelity.
A catalytic method for the synthesis of sterically hindered ethers and thioethers from α-bromo carbonyl compounds and the corresponding nucleophiles using an inexpensive Cu(I) catalytic system is ...reported. This facile transformation takes place at ambient temperature and does not require the exclusion of air or moisture; thus, it is well-suited for the functionalization and derivatization of complex organic molecules.
Herein we disclose an organocatalytic aryl–aryl bond-forming process for the regio- and atroposelective synthesis of 2,2′-diamino-1,1′-binaphthalenes (BINAMs). In the presence of catalytic amounts ...of axially chiral phosphoric acids, achiral N,N′-binaphthyl hydrazines undergo a facile 3,3-sigmatropic rearrangement to afford enantiomerically enriched BINAM derivatives in good to excellent yield. This transformation represents the first example of a metal-free, catalytic C(sp2)–C(sp2) bond formation between two aromatic rings with concomitant de novo atroposelective installation of an axis of chirality. Density functional calculations reveal that, in the transition state for C–C bond formation, the phosphoric acid proton of the catalyst is fully transferred to one of the N-atoms of the substrate, and the resulting phosphate acts as a chiral counterion.
A transition-metal free synthesis of highly functionalized 2-hydroxy-2′-amino-1,1′-biaryls from N-arylhydroxylamines has been developed. This operationally simple and readily scalable approach relies ...on a cascade of reactions that initially generates transient N,O-diarylhydroxylamines, via direct O-arylation, which then undergo rapid 3,3-sigmatropic rearrangement and subsequent rearomatization to form NOBIN-type products. These structurally diverse functionalized biaryls are obtained under mild conditions in good to excellent isolated yields.
Abstract In this paper the author argues that the Christmas holidays, notwithstanding their international standing as a religious and commercial season, are most productively understood as a glocal ...phenomena, a concept intended to link the local with the global in a dialectics of homogenization and particularism. Juxtaposing data from Hungary and Eastern Europe, the author provides an anthropological analysis that highlights the transformative power Christmas traditions and Santa Claus have played in diverse cultural settings since the late twentieth-century. For even the imposition of communist ideology, conceived as a globalizing force, failed to eradicate images of Santa Claus; both his persona and that of his devilish imp, Krampus, survived such ruthless attempts at indoctrination with only the slightest of modifications. In view of its economic and cultural significance, this paper argues in favor of international recognition of Saint Nicholas day, December 6 th, as a glocal civil holiday.
Postsocialist Europe Kurti, Laszlo; Skalnik, Peter
2009., 20090915, 2009, 2011-11-01, 20090101, Letnik:
10
eBook
Now that nearly twenty years have passed since the collapse of the Soviet bloc there is a need to understand what has taken place since that historic date and where we are at the moment. Bringing ...together authors with different historical, cultural, regional and theoretical backgrounds, this volume engages in debates that address new questions arising from recent developments, such as whether there is a need to reject or uphold the notion of post-socialism as both a necessary and valid concept ignoring changes and differences across both time and space. The authors’ firsthand ethnographies from their own countries belie such a simplistic notion, revealing, as they do, the cultural, social, and historical diversity of countries of Central and Southeastern Europe.
A transition-metal-free, regioselective direct aryl–aryl bond-forming process for the synthesis of halogenated 2-amino-2′-hydroxy-1,1′-biaryls that are currently either inaccessible or challenging to ...prepare using conventional methods is disclosed. The addition of ArMgX to an o-halonitrobenzene at low temperature generates a transient N,O-biarylhydroxylamine that rapidly undergoes either 3,3- or 5,5-sigmatropic rearrangement in one-pot to form a 2-amino-2′-hydroxy-1,1′-biaryl or 1-amino-1′-hydroxy-4,4′-biaryl, respectively. The periselectivity is controlled by the choice of solvent and temperature. This direct arylation process is also readily scalable (1–10 mmol). DFT calculations suggest that from the N,O-biarylhydroxylamine intermediate there is a low-energy stepwise pathway that involves initial Mg-mediated N–O bond cleavage followed by pathway branching toward either 3,3- or 5,5-rearrangement products via C–C bond formation and rearomatization.
We report the first direct catalytic enantioselective allylation of acyclic α-ketiminoesters to afford α-allyl-α-aryl and α-allyl-α-trifluoromethyl amino esters in excellent isolated yield (91–99%) ...and with high optical purity (90–99+% ee). The allylation proceeds on a gram scale with 5–10 mol % of indium(I) iodide and commercially available BOX-type ligands. The allylated products are easily converted to enantiomerically enriched α-substituted proline derivatives.
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