共查询到20条相似文献，搜索用时 15 毫秒
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Yu‐Peng Zhou Matthias Driess 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(12):3753-3766
A significant number of isolable silylenes are currently known. They have quickly developed from laboratory curiosities to useful ligands in metal‐mediated homogeneous catalysis. This includes their utilization in various catalytic transformations, such as C?C cross‐coupling, cyclotrimerization, hydroformylation, borylation, deuteration, hydrosilylation, amination, hydrogenation, and transfer semi‐hydrogenation reactions. Recent studies suggest that the silylene ligands surpass the steering properties of their phosphine and N‐heterocyclic carbene (NHC) analogues and provide excellent chemo‐, regio‐, and stereoselectivites. Mechanistic studies suggest that their promoted performance of metal‐mediated catalytic transformations results from a strong σ‐donor character along with cooperative effects of their SiII centers. This Minireview covers the most recent advances in the field. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(42):13246-13249
Among concerted cycloadditions, the Diels–Alder reaction is the grand old classic, which is usually achieved with acid catalysis. In this report, hydroxypyrones, oxa‐, and thiazolones are explored because they provide access to anionic dienes. Their [4+2] cycloaddition with cyclic and acyclic dienophiles, such as maleimides and fumarates, affords bicyclic products with four new stereogenic centers. Bifunctional anion–π catalysts composed of amine bases next to the π surface of naphthalenediimides (NDIs) are shown to selectively stabilize the “open”, fully accessible anionic exo transition state on the π‐acidic aromatic surface. Our results also include reactivities that are hard to access with conventional organocatalysts, such as the exo ‐specific and highly enantioselective Diels–Alder reaction of thiazolones and maleimides with complete suppression of the otherwise dominant Michael addition. With increasing π acidity of the anion–π catalysts, the rates, chemo‐, diastereo‐, and enantioselectivities increase consistently. 相似文献
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Andrew&#x;D. Abell Matthew&#x;A. Jones James&#x;M. Coxon James&#x;D. Morton Steven&#x;G. Aitken Stephen&#x;B. McNabb Hannah&#x;Y.‐Y. Lee Janna&#x;M. Mehrtens Nathan&#x;A. Alexander Blair&#x;G. Stuart Axel&#x;T. Neffe Roy Bickerstaffe 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2009,121(8):1483-1486
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Erica E. Schultz Nathaniel R. Braffman Michael U. Luescher Harry H. Hager Emily P. Balskus 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(10):3183-3187
The Friedel–Crafts alkylation is commonly used in organic synthesis to form aryl–alkyl C?C linkages. However, this reaction lacks the stereospecificity and regiocontrol of enzymatic catalysis. Here, we describe a stereospecific, biocatalytic Friedel–Crafts alkylation of the 2‐position of resorcinol rings using the cylindrocyclophane biosynthetic enzyme CylK. This regioselectivity is distinct from that of the classical Friedel–Crafts reaction. Numerous secondary alkyl halides are accepted by this enzyme, as are resorcinol rings with a variety of substitution patterns. Finally, we have been able to use this transformation to access novel analogues of the clinical drug candidate benvitimod that are challenging to construct with existing synthetic methods. These findings highlight the promise of enzymatic catalysis for enabling mild and selective C?C bond‐forming synthetic methodology. 相似文献
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Fernando Pirani David Cappelletti Stefano Falcinelli Diego Cesario Francesca Nunzi Leonardo Belpassi Francesco Tarantelli 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(13):4239-4243
Molecular‐beam scattering experiments and theoretical calculations prove the nature, strength, and selectivity of the halogen bonds (XB) in the interaction of halogen molecules with the series of noble gas (Ng) atoms. The XB, accompanied by charge transfer from the Ng to the halogen, is shown to take place in, and measurably stabilize, the collinear conformation of the adducts, which thus becomes (in contrast to what happens for other Ng‐molecule systems) approximately as bound as the T‐shaped form. It is also shown how and why XB is inhibited when the halogen molecule is in the 3Πu excited state. A general potential formulation fitting the experimental observables, based on few physically essential parameters, is proposed to describe the interaction accurately and is validated by ab initio computations. 相似文献
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Naoki Asao Pingli Liu Keiji Maruoka 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》1997,109(22):2616-2618
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