Acyclic amide group

Heterocyclic compounds carrying potential hydroxyl groups are cyclic amides or vinylogs of amides. There is much physical evidence that acyclic amides exist almost entirely in the oxo form (for references see reference 6), and the apparent contradiction that ultraviolet spectral data appeared to favor the imidol formulation has now been explained on steric grounds. The value of pKr is estimated to be about 7 on the basis of pK measurements for acyclic amides. Extensive evidence, summarized in the following sections, shows that for a- and y-hydroxy heterocyclic compounds, the cyclic amide form usually predominates by a substantial factor, often ca. 10 . 

To test this hypothesis further, simple acyclic cobaltocenium derivatives (Fig. 38) containing tertiary amide groups ([72] and [73]) were prepared and complexation with Cl- and Br anions was investigated in solution by nmr spectroscopy. No shifts of the host s proton resonances were observed, emphasizing again the importance of the amide N—H group in anion binding. 

In a related set of reactions, Oku and coworkers have been investigating the anodic oxidation of acyclic amides having alkoxy groups on the carbon alpha to the amide carbonyl (91) [61]. The direct... 

Secondary acyclic amides in the solid state display an amide II band in the region of 1570-1515 cm-1. In dilute solution, the band occurs in the 1550-1510 cm-1 region. This band results from interaction between the N—H bending and the C—N stretching of the C—N—H group. A second, weaker band near 1250 cm-1 also results from interaction between the N—H bending and C—N stretching. 

As with acyclic amides, enantiospecific discrimination of the enantiomers of a racemic substrate sometimes occurs. This phenomenon could prove useful in preparing new homochiral synthons. For example the two C-1 enantiomeric amides (32) and (33) are hydroxyla on different methyls (relative to the r-amide nitrogen) of the C-8 gem-dimethyl bridging group, as shown in Scheme 7. Hydroxylation of one methyl in a gem-dimethyl grouping by microorganisms is fairly common, and other examples are given later and elsewhere. ... 

Amide group scission (termed as cA-elimination mechanism) and intramolecular rearrangement of two amide groups, leading to cyclic compounds [20] are the main pyrolysis reactions in acyclic polyamides. The former reaction is outlined in Scheme 12.1b and the ester exchange drawn in Scheme 12.2 is analogous to the latter one. 

With the powerful formylation reagent IV -diformylacetamide imides are obtained from amides or lactams in good yield (equation 56). Oxidation reactions also have found some application in the synthesis of imides. For example, catalytic amounts of ruthenium tetroxide and 10% aqueous NaI04 as cooxidant in an optimized reaction medium (ethyl acetate-water) oxidize acyclic amides to imides. The reaction rate is inversely related to the electron-withdrawing power of the acyl group, i.e. the electron density at the nitrogen atom (equation 57). 

Also soon after the first crystal structure of ER, more traditional structure-based design work started to appear. The group of Stauffer et al. [113] used an acyclic amide structural template combined with the ER crystal structure to find additional hydrogen bonds and increase affinity. A number of separate groups, with just a few mentioned here [114-116], have utilized the crystal structure complexes to generate receptor-based alignment for a series of compounds, which were in turn used to generate predictive 3D-QSAR models. 

In Table A.l the chemical environment of each bond is normally defined by a linear formulation of the substructure. The target bond is set in bold type, e.g. Cgr-C N (aryl cyanides) C-CH2-0-Cgr (primary alkyl aryl ethers) (C-0)2-P( = 0)2 (phosphate diesters). Occasionally the chemical numbering of a functional group or ring system is used to define bond environment, e.g. in naphthalene, C(2)-C(3) in imidazole N1-C2. To avoid any possible ambiguity in these cases, we include numbered chemical diagrams in Figure A.4. A combination of chemical name and linear formulation is often employed to increase the precision of the definition, e.g. NH2-C=0 in acyclic amides C = C-C( = 0)-C(=0) in benzoquinones. Finally, for very simple ions the accepted conventional representation is deemed to be sufficient, e.g. in N03, S04, etc. 

The present procedure was successfully applied to Oxidation-Reduction Hydration of various olefins. As shown in Table 3, both of acyclic and cyclic olefins were hydrated in high yields based on cobalt(II) catalyst. Exo- and trisubstituted olefins were converted into the corresponding tertiary alcohols in more than 10000% yield based on the catalyst (Entries 2 and 4 in Table 3). Also, olefinic compounds having functional groups such as ester, acetal and amide groups were hydrated into the corresponding alcohols in high yields without any decomposition. 

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