N-Imides

There are various photochemical transformations of pyridazines, their corresponding benzo analogs, N-oxides and N-imides. Gas-phase photolysis of pyridazine affords nitrogen and vinylacetylene as the main products. Perfluoropyridazine gives first perfluoropyrazine, which isomerizes slowly into perfluoropyrimidine. 

Azolinones, azolinethiones, azolinimines N-Oxides, N-imides, N-ylides of azoles Thermal and Photochemical Reactions Formally Involving No Other Species 2.1 Thermal fragmentation... 

H-Benzo[a]carbazole, 4,4a,5,l 1,1 la,l Ib-hexahydro-synthesis, 4, 283 Benzo[b]carbazole, N-acetyl-photochemical rearrangements, 4, 204 Benzo[/]chroman-4-one, 9-hydroxy-2,2-dimethyl-synthesis, 3, 851 Benzochromanones synthesis, 3, 850, 851, 855 Benzochromones synthesis, 3, 821 Benzocinnoline-N-imide ring expansion, 7, 255 Benzocinnolines synthesis, 2, 69, 75 UV, 2, 127 Benzocoumarins synthesis, 3, 810 Benzo[15]crown-5 potassium complex crystal stmcture, 7, 735 sodium complex crystal stmcture, 7, 735 Benzo[ 18]cr own-6 membrane transport and, 7, 756 Benzo[b]cyclohepta[d]furans synthesis, 4, 106 Benzocycloheptathi azoles synthesis, 5, 120... 

Figure 3. Plastocyanin orientations. The Cu(N-Imid)2(S-Cys)(S-Met) unit has approximately trigonal pyramidal symmetry, with the S(Met) ligand at the apex of the pyramid. Key top, orientation giving predominantly Cu-S(Met) EXAFS and bottom, orientation giving no Cu-S(Met) EXAFS. (Reproduced from Ref. 30. Copyright 1982, American Chemical Society.)...

The use of N-glycosyl amides as glycosyl donors was reported by Pleuss and Kunz [240]. These amides were activated by Ph3P and CBr4 to produce bromo-N-imidates, which were spontaneously converted into the corresponding bromide concomitant with releasing nitrile, and then coupled with alcohols by activation with AgOTf (Scheme 5.86). 

A number of monocyclic and benzo-annelated examples of 1,2- and 1,3-thiazepines have been prepared but there has been little systematic study of these systems. The interesting photochemical interconversions of pyridine N-imides into 1,2- and 1,3-diazepines and of pyridine Af-oxides into 1,2- and 1,3-oxazepines regrettably lack parallels in thiazepine chemistry. There has been more interest in 1,4-thiazepines, as both rearrangement products and possible biogenetic precursors for penicillins and because of the pharmacological value of the benzo- and dibenzo-[l,4]thiazepines as antidepressants and coronary vasodilators. The only review (70ZC361) is excellent but not very recent. 

Clearly different ligand types will favor different oxidation states. Higher oxidation states prefer hard acid donor atoms, generally first-row p-block elements, rich in electron density and capable of strong a donation. A further provision is that they should resist oxidation. Common donor chromophores which have been used are amines N, imides (including oximes and imines)I>N , oxides —0 and fluorides F-. Second- and third-row p-block donors have also been used, forming bonds which are more covalent in character and creating special problems, as discussed below. 

Substituted tetrazolium N-aminides (N-imides) have been prepared by D. Moderhack and M. Noreiks via the tetrazolium salts and fully characterized. The tetrazolium aminides are reasonably stable solids with mp 85-229 °C. The preferred geometries of tetrazolium N-aminides have been determined by Hartree-Fock and density functional theory calculation <2004H(63)2605>. 

Tsuchiya, T., Kurita, J. and Takayama, K. (1980) Studies on diazepines. XIII. Photochemical behaviour of pyrazine, pyrimidine, and pyridazine N-imides. Chemical el Pharmaceutical Bulletin, 28 (9), 2676-2681. 

The available data suggest that in aqueous solution and at neutral pH prolyl isomerization proceeds according to a simple, one-step mechanism. Solvent water does not participate in the reaction and there is no accumulation of intermediates. The energy barrier to isomerization is enthalpic and represents the energy of resonance stabilization that is possessed by the C—N imide bond. 

As indicated above, the barrier to prolyl cis—trans isomerization is the resonance stabilization energy that is possessed by the C-N imide bond. The task of a prolyl isomerase is, therefore, to develop an enzymatic-chemical strategy that will result in the lowering of this barrier. When one reflects on the strategies that might be used by an enzyme, one realizes that there are two general mechanisms catalysis by distortion and nucleophilic catalysis (see Scheme V). 

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