Amidines effects

In the oxidative Eschenmoser sulfide contraction (Scheme 11), thioamide 59 is oxidized by benzoyl peroxide to give either a symmetrical disulfide or the O-benzoate of the thiolactam-S-oxide. In any event, the once-nucleophilic thioamide sulfur atom is now forced to adopt the role of electrophile a reactivity umpolung has, in effect, been achieved.13 The nucleophilic enamide 65 attacks the sulfur atom leading to the formation of sulfur-bridged intermediate 66. The action of a phosphine or a phosphite thiophile on the putative episulfide then gives vinylogous amidine 67. 

Complete reduction of the azepine ring to hexahydroazepine has been effected with hydrogen and palladium,40 or platinum,135 239 catalysts. For example, ethyl 1 f/-azepine-l-carboxylate is reduced quantitatively at room temperature to ethyl hexahydroazepine-l-carboxylate (92% bp 118 —120 3C).134 136 TV-Phenyl-S/Z-azepin -amine (1), however, with platinum(IV) oxide and hydrogen in methanol yields the hexahydroazepine 2 in which the amidine unit is preserved in the final product.34 The same result is obtained using 5% palladium/barium carbonate, or 2 % palladium/Raney nickel, as catalyst. 

Chromium, (ri6-benzene)tricarbonyl-stereochemistry nomenclature, 1,131 Chromium complexes, 3,699-948 acetylacetone complex formation, 2,386 exchange reactions, 2,380 amidines, 2,276 bridging ligands, 2,198 chelating ligands, 2,203 anionic oxo halides, 3,944 applications, 6,1014 azo dyes, 6,41 biological effects, 3,947 carbamic acid, 2,450 paddlewheel structure, 2, 451 carboxylic acids, 2,438 trinuclear, 2, 441 carcinogenicity, 3, 947 corroles, 2, 874 crystal structures, 3, 702 cyanides, 3, 703 1,4-diaza-1,3-butadiene, 2,209 1,3-diketones... 

The reaction of the coordinatively unsaturated ruthenium amidinates with [Cp RuCl]4 tetramer or [CpRufMeCNlsJPFg provides access to novel amidinate-bridged dinuclear ruthenium complexes (Scheme 146), which in turn can be transformed into cationic complexes or hydride derivatives. In these complexes, a bridging amidinate ligand perpendicular to the metal-metal axis effectively stabilizes the highly reactive cationic diruthenium species. 

Coordination numbers ranging from five to seven were observed, and they appeared to be controlled by the steric bulk of the supporting amidinate and coligands. Complexes 2-5 and 7 were found to be active catalysts for the pol3uneiization of D,L-lactide (e.g., with 2 and added benzyl alcohol, 1000 equiv of D,L-lactide were polymerized at room temperature in <1 h). The neutral complexes 2, 5, and 7 were more effective than the anionic complexes 3 and 4. ... 

As in 10-55 hydrazides and hydroxamic acids can be prepared from carboxylic esters, with hydrazine and hydroxylamine, respectively. Both hydrazine and hydroxylamine react more rapidly than ammonia or primary amines (the alpha effect, p. 445). Imidates, RC(=NH)OR, give amidines, RC(=NH)NH2. Lactones, when treated with ammonia or primary amines, give lactams. Lactams are also produced from y- and 5-amino esters in an internal example of this reaction. 

Values of pKa for substituted amidines were correlated with the Hammett equation by Charton (190). Data are available for one set of substituted amidinium ions and one set of C-substituted-N-phenylamidinium ions. The sets studied are shown in Table XXX. Results of the correlations are set forth in Table XXXI and values of pj in Table XXXII. Significant correlations were obtained for both sets. In the case of the ionization of N-phenyl amidinium ions, the possibility of tautomerism exists, Charton (170) has presented arguments which suggest that the predominant tautomer is 30. The localized effect is predominant in both of the sets of amidinium ions studied. 

In a recent study on the ICOR-channel we have compared the effect of NPPB to that of the disulphonate stilbenes (Fig. 2), IAA-94 (Fig. 2) and amidine (Fig. 2). We found that all these compounds induced a flicker-type block. NPPB showed the highest affinity [63]. The results of this study were perplexing inasmuch as compounds which appear to be chemically different, and even possess opposite net charges, exert comparable effects. In further studies on the ICOR channel others and we were able to show that unsaturated fatty acids, bumetanide, the buffer HEPES and even Ca -antagonists such as verapamil inhibited the ICOR channel... 

The structural arrangement of group 11 amidinate complexes is determined by the substituents on the amidinate aryl groups as well as on the NCN carbon [14,19]. The electronic vs. steric effect of the substituents on the molecular arrangement of gold(I) amidinate complexes have been studied in detail in the Fackler laboratory. 

Interaction of iV-pentafluorophenylcarbonimidoyl dichloride with benzonitrile and aluminium trichloride leads to l-pentafluorophenyl-4,6-diphenyl-13 -triazin-2-one along with urea derivatives . Reaction of perfluoro-5-azanon-4-ene with a range of bidentate nitrogen nucleophiles (urea, substituted amidine hydrochlorides and guanidine), in the presence of triethylamine or potassium hydroxide, effectively provides fluorinated 1,3,5-triazines 16-19 <00JFC(103)105>. 

The alternative possibility of protonation of amidines on the amino-nitrogen depends on its basicity, after its lone pair of electrons has been localized. This localization energy is not known and neither is the inductive effect of the residue attached to the amino-nitrogen in [36], but an amino-nitrogen attached to an -hybridized carbon... 

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