Pyridine monosubstituted

A series of complexes of the types ML X and ML X have been examined both in the solid state and in solution in organic solvents M = Co(II). Ni(II) or Zn(II) L = pyridine, monosubstituted pyridine, quinoline or isoquinoline ... 

Table 7.64 Nitrogen-15 Chemical Shifts in Monosubstituted Pyridine 7.115...

Four multiplets between Sh = 7.46 and 9.18 indicate monosubstitution of the pyridine ring, either in the 2- or 3-position but not in the 4-position, since for a 4-substituted pyridine ring an AA XX system would occur. The position of the substituents follows from the eoupling eonstants of the threefold doublet at Sh = 7.46, whose shift is appropriate for a p-proton on the pyridine ring (A). 

Using the processes described above, complex products are obtained if a monosubstituted phenol is used instead of a 2,6-substituted material. However, by using as the amine" a 2-disubstituted pyridine such as 2-amylpyridine, more linear and, subsequently, useful polymers may be obtained. 

The infrared spectra of amino- and methylamino-pyri-dines and -quinolines show absorption bands that are charcteristic of monosubstituted-pyridine " or -quinoline rings and of the amino group. Changes in the infrared and ultraviolet spectra of amino-... 

Whereas only one dehydrobenzene, benzyne, has been detected, two pyridynes are possible. Thus, the scheme we can write ab initio for the action of a nucleophile on the isomeric monosubstituted derivatives of pyridine involving 2,3- (26) and/or 3,4-pyridyne (31) is more complicated than that for the analogous reaction of the corresponding benzene derivative. The validity of this scheme can be checked using data available in the hterature on reactions of halogenopyridines with potassium amide and hthium piperidide involving pyridynes. 

It has been shown that even the labile monosubstituted butadiynyl derivatives ean be used as the starting terminal alkynes. Thus, the oxidative eoupling of 3-butadiynyl-l-methyl-, 5-butadiynyl-l-methyl-, and 4-butadiynyl-l,3,5-dimeth-ylpyrazole in pyridine by oxygen in the presenee of CuCl at room temperature leads to eonjugated oetatetraynes in 75%, 83%, and 84.0% yields (69IZV2546 69KGS1055) (Seheme 65, Table XVIII). 

Malonsaurc-dinitrile und deren Monosubstitutions-Produkte werden zu 3-Imino-pro-pansaure-nitrilen reduziert, die sich zu3-Amino-acrylnitrilen isomerisieren. So erhalt man z.B. aus Malonsaure-dinitril selbst 40% d.Th. cis- und trans-3-Amino-acrylnitril neben 7% d. Th. 2-Amino-3-cyan-pyridin (bei langer Reaktionsdauer und Lithiumalanat-Ober-schuG auch 2% d.Th. 3-Cyan-pyridin) ... 

In many instances it is not necessary to isolate the acetonitrile complex or to carry out the reaction in acetonitrile. The use of amine oxide as a means of displacing carbonyl groups in metal carbonyls is well documented, and reaction proceeds smoothly with the carbonyl in the presence of a variety of ligands—e.g., ethylene or pyridine—to yield the monosubstituted derivatives. The advantage of the acetonitrile adducts is the stability of the compounds and the reactivity of the amine oxide toward acidic ligands. 

To estimate the dispersion interaction contribution to the overall interaction between stacked rings we studied, in parallel with the role of electrostatics in Section 27.3.2, the interaction between monosubstituted benzenes Ph-X (X = H, F, NH2, Cl, CH3, OH, CN, COOH, CHO, N02) and pyridine, a simpler case with only one H-bond accepting site [58], and cytosine (with two H-bond accepting sites). An offset parallel geometry was chosen, keeping the X group and the N atom of pyridine at maximal distance, the level used being MP2/6-31G (0.25)//MP2/6-31G with BSSE correction [68]. 

Because of n-electron donation by the heteroatom, these carbene complexes are generally less electrophilic at C than the corresponding non-heteroatom-substituted complexes (Chapter 3). This effect is even more pronounced in bis-heteroatom-substituted carbenes, which are very weak Tt-acceptors and towards low-valent transition metals show binding properties similar to those of phosphines or pyridine. Alkoxycarbenes, on the other hand, have electronic properties similar to those of carbon monoxide, and stable heteroatom-monosubstituted carbene complexes are also usually formed from metals which form stable carbonyl complexes. 

A recent communication is based on the nucleophilic substitution of N-silylated iminophosphoranes (Scheme 8), where activated chloro- (12) and nitro heterocycles (13) (triazines, pyrazines, and pyridines) are transformed into monosubstituted iminophosphoranes (14). Of special advantage are the mild reaction conditions and the preferential formation of monosubstituted... 

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