Amides dehydrogenation

Although hydrogenation of the 2 1 alanate-amide dehydrogenation products was not attempted, there is no reason to believe this reaction will not also stop at the formation of LiH and LiNH2 like those for the 1 1 and 1 2 ratios. 

S DibTomo-2,3-dimethylbutanelsodium amide Dehydrogenation via organodisodium compounds... 

Amide-induced pyridine-pyrimidine transformation is also reported with 2-bromo-l, 5-naphthyridine. 2-Methyl-4-amino-l, 3,5-triazanaphtha-lene is obtained, together with its 4-amino derivative The presence of the amino group at position 4 is certainly due to a SnH amino-dehydrogenation in preformed 2-methyl-l,3,5-triazanaphthalene (63RTC997, 73RC459, 94MI1). 

The initial synthesis of papaverine is due to Pictet, and fittingly enough involved as its key step the name reaction. Acylation of veratrylamine (109) with dimethoxyphenylacetylchlo-ride affords the amide (110). Cyclization by means of phosphorus oxychloride constitutes the same reaction and affords the dihy-droisoquinoline (111). Dehydrogenation by means of a noble metal catalyst affords papaverine (107). ... 

A variant on this structure, dioxyline, has much the same activity as the natural product but shows a better therapeutic ratio. Reduction of the oxime (113) from 3,4-dimethoxyphenyl-acetone (112) affords the veratrylamine homolog bearing a methyl group on the amine carbon atom (114). Acylation of this with 4-ethoxy-3-methoxyphenyl acetyl chloride gives the corresponding amide (115). Cyclization by means of phosphorus oxychloride followed by dehydrogenation over palladium yields dioxyline (116). ... 

This section contains dehydrogenations to form alkenes and unsaturated ketones, esters and amides. It also includes the conversion of aromatic rings to alkenes. Reduction of aryls to dienes is found in Section 377 (Alkene-Alkene). Hydrogenation of aryls to alkanes and dehydrogenations to form aryls are included in Section 74 (Alkyls from Alkenes). 

Some companies are successfully integrating chemo- and biocatalytic transformations in multi-step syntheses. An elegant example is the Lonza nicotinamide process mentioned earlier (.see Fig. 2.34). The raw material, 2-methylpentane-1,5-diamine, is produced by hydrogenation of 2-methylglutaronitrile, a byproduct of the manufacture of nylon-6,6 intermediates by hydrocyanation of butadiene. The process involves a zeolite-catalysed cyciization in the vapour phase, followed by palladium-catalysed dehydrogenation, vapour-pha.se ammoxidation with NH3/O2 over an oxide catalyst, and, finally, enzymatic hydrolysis of a nitrile to an amide. 

Synthesis of 216, an analog of the amide alkaloids, starting with ketone 214 was performed by Ishii et al. (176) (Scheme 33). The initial step involved the formation of cis secondary amine 215, which on N-formylation and dehydrogenation led to 216. Under Bischler-Napieralski conditions 216 could be recyclized to chelirubine (217). 

Dehydrogenation of hydrazo compounds with bromine, 32, 16 Dehydrohalogenation by sodium amide, 30, 72... 

Piperidine derivatives 161 and 164 could be cyclized to hexahydropyridooxadiazines 162, 165 via a dehydrogenation process by six oxidation equivalents of Hg(n)-EDTA. However, in both reactions, side products were also formed. From 161, piperidone derivative 163 was obtained, whereas starting from the amide 164, pyridopyrimidine 166 was isolated via cyclization by the amide nitrogen instead of oxime oxygen (Scheme 21) <1999ZNB632>. 

Biosynthesis of the polypeptide chain is realised by a complicated process called translation. The basic polypeptide chain is subsequently chemically modified by the so-called posttranslational modifications. During this sequence of events the peptide chain can be cleaved by directed proteolysis, some of the amino acids can be covalently modified (hydroxylated, dehydrogenated, amidated, etc.) or different so-called prosthetic groups such as haem (haemoproteins), phosphate residues (phosphoproteins), metal ions (metal-loproteins) or (oligo)saccharide chains (glycoproteins) can be attached to the molecule by covalent bonds. Naturally, one protein molecule can be modified by more means. 

C-H activation remains an important topic for catalysis even after thirty years of intensive research. The potential shortcuts it offers for many present routes to a wide variety of chemicals that are produced will continue to inspire industrial and academic research [32], An interesting example involves the enantiospecific, coordination-directed C-H bond functionalisation in the synthesis of a natural product, rhazinilam, an anti-tumor agent. The resulting vinyl moiety obtained in the dehydrogenation was subsequently carbonylated to form a cyclic amide [33],... 

L.L. Shaw, R. Ren, T. Markmaitree, W. Osborn, Effects of mechanical activation on dehydrogenation of the lithium amide and lithium hydride system , J. Alloys Compd. 448 (2008) 263-271. 

Synthesis of secondary amides via the oxidative coupling (dehydrogenation) of primary alcohols R CH3(OH) and primary amines R (CH3)NH3 to the amides... 

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