N- adduct

The bulky ruthenium TMP complex Ru(TMP) is very electron deficient in the absence of any coordinating ligand, and a tt-complex with benzene has been proposed. In fact, it readily coordinates dinitrogen, forming the mono- and bis-N adducts Ru(TMP)(N2)(THF) and Ru(TMP)(N2)2, - As a result, the use of the TMP ligand for careful stereochemical control of the chemistry at the metal center, which has been very successful for the isolation of elusive rhodium porphyrin complexes, is less useful for ruthenium (and osmium) because of the requirement to exclude all potential ligands, including even N2,... 

The reaction with valerolactam 24 was also investigated, with surprising results. The reaction with BSTFA gave the silyl lactam 78 rather than the silyl imidate 25, as shown in Scheme 3.33. Subsequent reaction with DDQ gave a C-N adduct 79... 

Pietrzyk, P., Piskorz, W., Sojka, Z. et al. (2003) Molecular structure, spin density distribution, and hyperfine coupling constants of the i7l CuNO n adduct in the ZSM-5 zeolite DFT calculations and comparison with EPR data, J. Phys. Chem. B., 107, 6105. 

The possible mechanisms of inhibition of flavin by (—)-deprenyl, as an irreversible acetylenic inhibitor, were studied by ab initio methods with the 6-31G basis set using simplified model compounds, 3-formyl-2-imino-l-hydroxypyrazine, and propargylamine. The formation of two energetically stable cyclic adducts, the 0,N adduct 286 and a C,N adduct, was shown <1999THA147>. 

The N-adducts derived by reaction of 1,5-diaminoimidazoles (96 R = NHPh, R2 = aryl, /Pr) with the /V-acylimidates (140) and (141) were cyclized smoothly in hot xylene solution to give the corresponding purines (168) and (169) in good yield (85MI1). 

Boche and co-worker ° carried out detailed studies of the decomposition reactions of various A -hydroxylamine esters in the presence of DNA and deoxygua-nosine, and characterized the adducts that resulted from these reactions. Thus, the nitrenium ion derived from 0-acetyl-N-(2-aminofluorene) added to DNA to give an adduct joining the C8 position of the base with the nitrenium ion nitrogen. Similar experiments carried out with the precursor of 2-naphthylnitrenium ion gave N2-ortho 148 and C8-N adducts 149 as shown in Figure 13.72. ... 

A different course is followed by a substrate in the above series when the R substituents are sufficiently acidic (R = NHMe, NHPh, CH2Ph). Formation of the monoanionic conjugate base by proton abstraction from the substituent reduces the tendency toward adduct formation. However, with the latter group of substrates the final product is a 4-amino-2-R-pyrimidine, which presumably is derived from the conjugate base by the intermediacy of a (nondetected) dianionic 1 1 n-adduct.103... 

The powerfully electrophilic character of 4,6-dinitrobenzofuroxan is further illustrated by the fact that ketones of low acidity, such as acetone and cyclopentanone, form n-adducts by carbon attachment to the 7-position... 

As for other heterocyclic systems (see Sections II and III) n-adduct formation in the benzofurazan and benzofuroxan series can be monitored on the basis of UV-visible spectral changes.33,202,208,209,215,216,220-223... 

The synthesis of the pyrimidine ring represents a well-studied group of heterocyclization reactions based on enamines. One of the important approaches involves the reaction of enamines with assorted isocyanates and isothiocyanates. Thus, a reaction of enaminonitriles with benzyl isocyanate or phenyl isocyanate gives C- and N-adducts (190a and 190b, respectively) or their mixtures, which are transformed in a single step into 4-pyrimidinone (191) and 2-pyrimidinone (192) derivatives (94JHC329). The... 

For the study on the formation of n adducts between parent azines or their derivatives, and potassium amide in liquid ammonia, we refer to reference 21 and the literature cited therein. 

When the temperature was allowed to increase from —40 to about 10 C, no change of the H- and UC-NMR spectra was observed,16 indicating that 5 is also thermodynamically most favored. In n-adduct 5 there is a notable contribution of the para-para quinoid structure3 (5b) because it leads to a considerable negative charge on N-6. This para-para quinoid resonance structure has already been discussed as an important contribution in stabilization of adduct 2 (see Section II,A,1). It explains why adduct 6 is not formed even under conditions that are favorable for thermodynamic control. Apparently the azaallylic contribution (6b) is of less importance than the para-para quinoid contribution (5b) when a nitrogen is present at position 6. 

The mechanism of the Chichibabin amination of pyridine has been discussed in terms of an addition-elimination mechanism via a covalent a-adduct.38 39 The possible formation of 2,3-didehydropyridine (2,3-pyridyne) as intermediate in the Chichibabin amination has been advocated, but this is now definitely rejected.38 39 In this section we discuss the Chichibabin amination of the parent naphthyridines and their derivatives and the products that are obtained in these aminations. The formation of their precursors (the covalent n-adducts) has already been discussed in Section II,A and II,B. 

In 2002, Yamamoto and Momiyama reported an unusual aldol-like reaction with silyl enol ethers and nitrosobenzene in the presence of a catalytic amount of TESOTf (nitrosoaldol reaction).29 Usually, nucleophiles react with nitrosobenzene without Lewis acid to give the N adduct predominantly. In contrast, they reported that the reaction of silyl enol ethers and nitrosobenzene catalyzed by TESOTf afforded the... 

In contrast, the reaction of tributyltin enol ethers and nitrosobenzene in the presence of a 1 2 mixture of BINAP and AgOTf in ethylene glycol diethyl ether afforded the N adduct predominantly with high enantioselectivity (Table 9.13). Momiyama and Yamamoto have determined the structures of silver-BINAP complex by an X-ray analysis and a 31P NMR study3015. 

Snp23 fr>h ph Y P-AgOTf AgOTf Ph O pH RlJ X Ph R2R3 N adduct O + RlAX° NHPh R2R3 O adduct... 

Alternatively, (217) react with activated methylene synthons in the presence of potassium bicarbonate to afford transient C=N adducts (218) which revert to the 4-amino-5-(/ ,/ -di substituted vinyl)triazoles (219) or (220). Recyclization of these products (219) or (220) affords (215). Similar transformations of l-substituted-l/7-pyrazolo[3,4-J]pyrimidines (77CPB535), pyrido[2,3-t/]py-rimidines (75CPB2939, 78CPB3242), and quinazolines <79CPB286l> have also been reported. 

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