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Lewis acids and bases
About: Lewis acids and bases is a research topic. Over the lifetime, 29508 publications have been published within this topic receiving 631764 citations. The topic is also known as: Lewis acids and bases.
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TL;DR: The Mukaiyama-aldol reaction, known to require much more active Lewis catalysts, is also catalyzed in the presence of 1, representing the first such example for a metal-organic framework.
Abstract: Treatment of selected aldehydes and ketones with cyanotrimethylsilane in the presence of the microporous metal-organic framework Mn3[(Mn4Cl)3BTT8(CH3OH)10]2 (1, H3BTT = 1,3,5-benzenetristetrazol-5-yl) leads to rapid conversion to the corresponding cyanosilylated products. The transformation is catalyzed by coordinatively unsaturated Mn2+ ions that serve as Lewis acids and lead to conversion yields of 98 and 90% for benzaldehyde and 1-naphthaldehyde, the highest thus far for a metal-organic framework. Larger carbonyl substrates cannot diffuse through the pores of 1, and conversion yields are much lower for these, attesting to the heterogeneity of the reaction and its dependence on guest size. The Mukaiyama−aldol reaction, known to require much more active Lewis catalysts, is also catalyzed in the presence of 1, representing the first such example for a metal-organic framework. Conversion yields obtained for the reaction of selected aldehydes with silyl enolates reach 63%, on par with those obtained with ze...
772 citations
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TL;DR: The Lewis acids (CH3)3SiOSO2CF3 (3), CH3 5S iOSO2C4F9 (6), and CH3 3SiClO4 (4) are highly selective and efficient Friedel-Crafts catalysts for nucleoside formation form silylated heterocycles and peracylated sugars as discussed by the authors.
Abstract: The novel Lewis acids (CH3)3SiOSO2CF3 (3), (CH3)5SiOSO2C4F9 (6), and (CH3)3SiClO4 (4) are highly selective and efficient Friedel-Crafts catalysts for nucleoside formation form silylated heterocycles and peracylated sugars as well as for rearrangements of persilylated protected nucleosides. With basic silylated heterocycles these new catalysts give much higher yields of the natural N-1-nucleosides than with SnCl4.
772 citations
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TL;DR: In this article, the surface properties of high surface area ceria samples, either in the reduced or unreduced state, have been investigated using FT-IR spectroscopy.
755 citations
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TL;DR: It is shown that more nucleophilic and electrophilic (alkyl)(amino)carbenes can activate H2 under mild conditions, a reaction that has long been known for transition metals.
Abstract: In possessing a lone pair of electrons and an accessible vacant orbital, singlet carbenes resemble transition metal centers and thus could potentially mimic their chemical behavior. Although singlet di(amino)carbenes are inert toward dihydrogen, it is shown that more nucleophilic and electrophilic (alkyl)(amino)carbenes can activate H2 under mild conditions, a reaction that has long been known for transition metals. However, in contrast to transition metals that act as electrophiles toward dihydrogen, these carbenes primarily behave as nucleophiles, creating a hydride-like hydrogen, which then attacks the positively polarized carbon center. This nucleophilic behavior allows these carbenes to activate NH3 as well, a difficult task for transition metals because of the formation of Lewis acid-base adducts.
738 citations
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12 Sep 1991TL;DR: In this article, a monocyclopentadienyl or substituted cyclopentienyl metal complex containing compound useful as a polymerization catalyst corresponding to the formula: CpMX.n.sup.
Abstract: A monocyclopentadienyl or substituted monocyclopentadienyl metal complex containing compound useful as a polymerization catalyst corresponding to the formula: CpMX.sub.n.sup.+ A.sup.- wherein: Cp is a single η 5 -cyclopentadienyl or η 5 -substituted cyclopentadienyl group optionally covalently bonded to M through a substituent; M is a metal of Group 3-10 or the Lanthanide Series of the Periodic Table bound in an η 5 bonding mode to the cyclopentadienyl or substituted cyclopentadienyl group; X each occurrence independently is selected from the group consisting of hydride, halo, alkyl, aryl, silyl, germyl, aryloxy, alkoxy, amide, siloxy, neutral Lewis base ligands and combinations thereof having up to 20 non-hydrogen atoms, and optionally one X together with Cp forms a metallocycle with M; R is alkyl or aryl of up to 10 carbons; n is one or two depending on the valence of M; and A is a noncoordinating, compatible anion of a Bronsted acid salt.
724 citations