Henry reaction Subject

Reaction of nitromethane and monosaccharide-derived dialdehydes is a useful tool that has been broadly used for the preparation of nitro and amino sugars, and carbocycles.30 Dialdehydes can easily be obtained by oxidative cleavage of conveniently protected monosaccharides with sodium periodate. Their subsequent Henry reaction with a nitroalkene, commonly nitromethane, usually gives isomeric mixtures that require the isolation of the major isomer.31 Thus, treatment of the D-ribose derivative 27 with sodium periodate gave dialdehyde 28, which was subjected to a Henry reaction with nitromethane, to afford nitrosugar 29 as an epimeric mixture (Scheme 11).32... 

In a recent application of this strategy, nitrocyclohexane 143 (prepared from nitrosugar 142 by intramolecular Henry reaction) was subjected to a radical denitration by HSnBu3, after protection of the hydroxyl groups to avoid side reactions. Inositol 146 was selectively obtained in good yield, once the hydroxyl protecting groups were removed (Scheme 45).101... 

Both the Henry reaction and the reverse demethylolation are synthetically useful in the chemistry of polynitroaliphatic compounds. The Henry reaction is commonly used to mask the natural chemistry of an aliphatic nitro or terminal em-dinitro group by removing the acidic a -proton(s). In Section 1.7 we discussed the conversion of Q ,ty-dinitroalkanes to their bis-methylol derivatives before subjecting them to oxidative nitration and subsequent demethylolation with base, a procedure which results in the formation of Q ,Q , y, y-tetranitroalkanes. ... 

Caldarelli et al. (240) have recently reported a five-step synthesis of substituted p)Trole libraries L22 and L23 using solid-supported reagents and scavengers. The synthesis involved oxidation of benzyl alcohols Mi to aldehydes (step a, Fig. 8.46), Henry reaction of aldehydes 8.91 with nitroalkanes M2 (step b), and acylation and elimination of nitroalcohols 8.93 (steps c and d) to give the nitrostyrenes 8.94, which were subjected to 1,3-dipolar cycloaddition with an isocyanoacetate (step e) to give the pyrroles 8.95. N-alkylation of these pyrroles with alkyl halides (step f) and final library-from-a-library hydrolysis/decarboxylation of L22 gave a library of trisub-stituted pyrroles L23 (step g. Fig. 8.46). 

The synthesis of the bisbenzannelated spiroketal core of the y-rubromycins was achieved by the research team of C.B. de Koning." The key step was the Nef reaction of a nitroolefin, which was prepared by the Henry reaction between an aromatic aldehyde and a nitroalkane. The nitroolefin was a mixture of two stereoisomers, and it was subjected to catalytic hydrogenation in the presence of hydrochloric acid. The hydrogenation accomplished two different tasks it first converted the nitroalkene to the corresponding oxime and removed the benzyl protecting groups. The oxime intermediate was hydrolyzed to a ketone that underwent spontaneous spirocyclization to afford the desired spiroketal product. 

When the nitroalkene 125 was subjected to the three-step procedure of Michael addition of propargyl alcohol, Henry reaction, and intramolecular radical cyclization, the Incyclic structure 126 was obtained,... 

The bifunctional thiourea catalyst was anchored to the developed polymer and subjected to the Michael and aza Henry reactions [93]. 

Based on catalytic double activation (guanidinium salt/thiourea moiety skeleton), Nagasawa et al. were able to achieve the reaction of nitromethane, nitro-ethane, and nitropropane with aliphatic a-ketoesters in moderate yields and selectivities (Scheme 29.10) [24]. The reaction works with the assistance of 10 mol% KOH and to overcome the retro-nitroaldol reaction, the presence of 50mol% K1 was required. The resulting Henry reaction adducts are obtained with good syn/anti ratios, and enantioselectivities of up to 98%. When aromatic a-ketoesters were subjected to the reaction unsatisfactory results were obtained (e.g., R = Ph, 5% yield and 5% ee). 

In 1998, Anderson reported a diastereoselective synthesis of vicinal diamines involving acid-catalyzed aza-Henry (or nitro-Mannich) reactions of nitro-alkanes 296 with imines 297 (Scheme 11.38) (188). Subsequent reduction of the nitro group could be carried out with Sml2 to give the corresponding 1,2-anti diamines 299. The development of catalytic enantioselective aza-Henry reactions would provide access to such structurally important 1,2-diamino building blocks in optically active form and has been the subject of considerable attention [23, 189]. 

Another approach employing chiral acyclic azomethine ylides was published in two recent papers by Alcaide et al. (85,86). The azomethine ylide-silver complex (51) was formed in situ by reaction of the formyl-substituted chiral azetidinone (50) with glycine (or alanine) in the presence of AgOTf and a base (Scheme 12.18). Azomethine ylides formed in this manner were subjected to reaction with various electron-deficient alkenes. One example of this is the reaction with nitrostyrene, as illustrated in Scheme 12.18 (86). The reaction is proposed to proceed via a two step tandem Michael-Henry process in which the products 52a and 52b are isolated in a... 

The experimental quantity used to characterize heterogeneous reaction rates is the "reaction probablity", y, which is defined as the fractional collision frequency that leads to reactive loss. Kinetic data for the generally irreversible reactive uptake of trace gas species on condensed surfaces are expressed in terms of uptake experiments, where the disappearance of the species under consideration and/or the appearance of one or more reaction products has been observed. Such processes may not be rate limited by Henry s law constraints, however the fate of the uptake reaction products may be subject to saturation limitations. 

The first studies on this subject were apparently made by Haitinger (Ref 1) and then by Priebs(Ref 2). These were followed by Henry(Ref 3), Posner(Ref 4) and others. More recently Boileau(Ref 5) made alde-hyde-.nitroparaffin reactions the subject of his thesis. By means of these reactions he prepared a number of aliphatic nitro-alcohols. He also studied the kinetics of aldehyde-niuoparaffin reactions conducted in a homogeneous medium and in the presence ofbasic catalysts Refs 1)L.Haitinger, Ann 193,366( 1878)... 

Henry Eyring s courses in statistical mechanics and reaction rate theory opened a new world to me when I took them in 1947-48 while a graduate student in physiology. My most vivid memories of these courses are the clarity of his lectures, his enthusiasm for his subject, and the insight he imparted into the behavior of matter at the molecular level. The brilliance of his lectures was emphasized when Henry was out of town and his post-doctoral students had to substitute for him they suffered in the inevitable comparison. 

The formation of the next intermediate, 5, in a hydroxypalladation step has been the subject of controversy over many years. According to his kinetic investigations, Henry postulated a syn-attack (cis-ligand insertion reaction) of a complexed OH ion to the complexed olefin (Eq. (9.7)). 

Under natural conditions unspontaneous and spontaneous processes, as a rule, proceed simultaneously and are directed against each other. In chemistry their relationships are determined by Le Chatelier principle (Henry Le Chatelier, 1850-1936) if a system at the state of chemical equilibrium is subjected to external action, the systems equilibrium will be offset in the direction of the reaction, which counteracts the external action. 

The nature and properties of metal complexes have been the subject of important research for many years and continue to intrigue some of the world s best chemists. One of the early Nobel prizes was awarded to Alfred Werner in 1913 for developing the basic concepts of coordination chemistry. The 1983 Nobel prize in chemistry was awarded to Henry Taube of Stanford University for his pioneering research on the mechanisms of inorganic oxidation-reduction reactions. He related rates of both substitution and redox reactions of metal complexes to the electronic structures of the metals, and made extensive experimental studies to test and support these relationships. His contributions are the basis for several sections in Chapter 6 and his concept of inner- and outer-sphere electron transfer is used by scientists worldwide. 

In 1876, Henry J.H. Fenton publicly announced that the use of a mixture of H2O2 and Fe " (thereafter so-called Fenton s reagent) allowed the destruction of an organic compound, namely, tartaric acid [1], Such discovery triggered an intense research to elucidate the mechanistic fundamentals and propose different variants and applications of the Fenton process. The possible formation of Fe(IV) as an active Fenton intermediate, as well as the modeling of the real structure of the iron aqua complexes, is still the subject of discussion [2, 3]. However, at present, it is quite well established that the classical Fenton s reaction (1) involves the production of highly oxidative hydroxyl radicals ( OH) in the bulk as the main reactive species, and its optimum pH value is 2.8-3.0 [1] ... 

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