Aerobic dehydrogenation

In 2013, AstraZeneca researchers reported an application of copper-catalyzed aerobic dehydrogenative aromatization in the 120 g scale synthesis of AZD8926, a drug candidate for the treatment of central nervous system disorders (Scheme 5.6) [29]. This aerobic dehydrogenation process was determined to be superior for large-scale implementation over other oxidation methods, such as a benzoquinone-mediated oxidation and various protocols using peroxide-based... 

With GiO as carbocatalyst, oxidative cross condensations of various anihnes and ahphatic amines with benzyl amine to the corresponding Af-benzylidene derivatives have also been achieved by suppressing homocondensation of benzyl amine by using an excess of the cross-coupling partner [77]. Reduced GeO served as a reusable aerobic dehydrogenation catalyst for the preparation of azo compounds from their hydrazo precursors [79]. 

A diverse range of carbocycles and heterocycles has been aromatized by aerobic dehydrogenation under AC catalysis [80]. Substrates include 9,10-dihydroanthracenes [81], a l,8-diaza-9,10-dihydroanthracene [82], Hantzsch 1,4-dihydropyridines [83], pyrazolines [83], 2-arylimidazolines [84, 85], indolines [86], 3,4-dihydropyrimidin-2(l//)-ones [87, 88], and various... 

Heterocyclic) benzylamines have also been aerobically dehydrogenated by mpg-CN as a photocatalyst, yielding the corresponding Af-benzylidene products [122]. Coordination of the imine to a hole in the VB is thought to facilitate intermediate aminal formation by nucleophilic attack on the C=N double bond. Dehydrogenative aromatizations of several N-heterocycles have also been carried out with mpg-CN [122]. 

Cyclic ketones can be aerobically dehydrogenated to cyclic enones, using a new catalyst, Pd(DMSO)2(TFA)2. For cyclohexanones, complete oxidation to the phenol is typically avoided. ... 

S. K. Guchhait, K. Jadeja, C. Madaan, Tetrahedron Lett. 2009, 50, 6861-6865. A new process of multicomponent Povarov reaction-aerobic dehydrogenation synthesis of polysubstituted quinolines. 

This name is applied to the series of carriers along which pass the protons and electrons liberated in the course of a dehydrogenation in the tricarboxylic acid cycle or other aerobic dehydrogenation before they reach oxygen and unite with it to form water. As we have seen, it is along the respiratory chain that by a series of phosphorylations coupled to it by a still unknown mechanism (see p. 144) the main quota of energy-rich bonds is formed and placed at the disposition of the cells. 

Another interesting feature of Pd complexes is their ability to use oxygen as terminal oxidant for oxidative functionalizations. Several examples of oxidative C yi—H olefinations (oxidative Heck reactions) proceed with O2 as a reagent. Furthermore, aerobic dehydrogenative aryl couplings with high site selectivity have been developed. ... 

Scheme 12 Aerobic dehydrogenative cross-coupling of pentafluorobenzene with thiophene derivatives [49]...

Substituted thiophenes and polyfluoroarenes could be cross-coupled via a Pd-catalyzed aerobic dehydrogenative process (eq 17). ... 

Stoltz BM (2004) Palladium catalyzed aerobic dehydrogenation from alcohols to indoles and asymmetric catalysis. Chem Lett 33 362-367... 

The aerobic dehydrogenative annulation of 2-aryl-substituted pyrroles and indoles for a variety of alkynes, using the system ruthenium(Il) catalyst with oxidant Cu(0Ac)2.H20, was then reported. The reaction was now performed under ambient air as the ideal sacrificial oxidant, thus only 10 mol% of Cu (0Ac)2.H20 could be used for efficient transformations of indoles [(Eq. 89)] [178]. This method could also be applied to synthesize pyrrolo[2,l-a]isoquinolines from 2-arylpyrroles with dialkyl-, diaryl-, or alkylarylacetylenes with an excellent regioselectivity. The competition experiments showed that an electron-deficient alkyne favours this reaction and that the more acidic C-H bond activation is favoured [(Eq. 89)] [178]. 

The aerobic degradation of nicotine produces an A-methylpyrrolidine as the first metabolite by dehydrogenation. This is then hydroxylated at the benzylic carbon atom by an FAD-containing oxidase (Dai et al. 1968), and the y-A-methylaminobutyrate that is produced by fission of the A-methylpyrolidine ring is demethylated by an oxidase to 4-aminobutyrate (Chiribau et al. 2004). 

Aerobic degradation of chlorinated arene hydrocarbons, including the important group PCBs, and chlorobenzoates that are produced from them as metabolites, is generally initiated by dihy-droxylation of the rings to dihydrodiols followed by dehydrogenation to catechols. Halide may be lost simultaneously and for 2-halogenated benzoates, both halide and carboxyl. Salient aspects are summarized, and attention drawn to selected aspects of enzyme inhibition. 

This indicator possesses the advantage that it may be used under aerobic conditions, in contrast to dyes such as methylene blue (115). Resazurin has also been applied in the study of the dehydrogenation of isopropanol and sorbitol (103), (118). 

Ishii and co-workers [109] reported the aerobic oxidation of various organic compounds catalyzed by (NH4)5H6[PV8Mo4O40] supported on active carbon. The catalyst showed high activity for oxidative dehydrogenation of various benzylic and allylic alcohols to give the corresponding carbonyl compounds in moderate to high yields. The catalyst can be recycled without loss of activity for the... 

It is possible to prepare a lignin-like polymer, known as dehydrogenated polymerisate (DHP) in the laboratory by treating con-iferyl alcohol in vitro under aerobic conditions with a phenoloxidase... 

Fig. 5.1.8. Presumed major pathway for intracellular aerobic biodegradation of LAS (as acetyl-CoA derivatives) to SPC via w-oxidation followed by successive oxidative shortening of the alkyl chain by two carbon units ((3-oxidation). Intermediates of 13-oxidation, such as SPC-2H formed by enzymatic dehydrogenation, are also transported out of the cell after cleavage of the CoA...

This enzyme is commonly found in aerobic sulfur-oxidizing lithotrophs, but its importance as an alternative to a hydration-dehydrogenation electron-transport-linked energy-generating mechanism is still disputed (Kelly 1999) ... 

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