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The thiourea hydrogen bonds to the nitro group and stabilizes the incoming negative charge, while the amine acts a specific base to activate the nucleophile. This is an example of bifunctional catalysis. Hydrogen-bond catalysis is a type of organocatalysis that relies on use of hydrogen bonding interactions to accelerate and control organic ...
Homogenous catalysts for alcohol amination based on rhodium and ruthenium were developed by Grigg [8] and Watanabe [9] in 1981. The first hydrogen auto-transfer processes that convert primary alcohols to products of carbonyl addition were reported by Michael J. Krische in 2007-2008 using homogenous iridium and ruthenium catalysts. [10] [11] [12]
Hydrogen-bonding between thiourea derivatives and carbonyl substrates involve two hydrogen bonds provided by coplanar amino substituents in the (thio)urea. [2] [3] [4][5] Squaramide catalysts engage in double H-bonding interactions and are often superior to thioureas.
A squaramide organocatalyst typically contains the squaramide group and a hydrogen bond donor which is usually a tertiary amine group. The 3,5-bis(trifluoromethyl)phenyl-group is commonly used for the R group. For enantioselective squaramide catalysis, chirality is induced via the tertiary amine group. There are cases where both sides of the ...
Hydrogen bond: A hydrogen bond is a specific type of dipole-dipole interaction between a partially positive hydrogen atom and a partially negative electron donor that contain a pair of electrons such as oxygen, fluorine and nitrogen. The strength of hydrogen bond depends on the chemical nature and geometric arrangement of each group.
Researchers have since conducted increasingly detailed investigations of the triad's exact catalytic mechanism. Of particular contention in the 1990s and 2000s was whether low-barrier hydrogen bonding contributed to catalysis, [18] [19] [20] or whether ordinary hydrogen bonding is sufficient to explain the mechanism.
Pages in category "Catalysis" The following 159 pages are in this category, out of 159 total. ... Hydrogen spillover; Hydrogen-bond catalysis; Hydromethanation;
An ubiquitous example of a hydrogen bond is found between water molecules. In a discrete water molecule, there are two hydrogen atoms and one oxygen atom. The simplest case is a pair of water molecules with one hydrogen bond between them, which is called the water dimer and is often used as a model system. When more molecules are present, as is ...