3- pyridyl derivatives

There are now a number of X-ray structures for simple triazolopyridines, ylides, and metal complexes which show the molecular dimensions. The 3-pyridyl derivative 135 (94JCS(D)2651), the ester 136 (83AX(C)391), and the 3-hydroxy derivative 137 (99JMS(476)289) provide dimensions for systems 1, 2, and 4, and are shown in Fig. 2. 

If the free-base porphyrin is tetrasubstituted at the meso positions with 3- or 4-pyridyl ligands, pentamers are obtained on coordination to zinc porphyrin dimers (79) (65,66, Fig. 24). With the 3-pyridyl derivative all the porphyrin planes are coplanar, whereas in the case of the 4-pyridyl derivative the ligand porphyrins are approximately perpendicular to the plane of the zinc porphyrins. Quenching of the zinc porphyrin... 

Electrochemical impedance spectroscopy was used to determine the effect of isomers of 2,5-bis( -pyridyl)-l,3,4-thiadiazole 36 (n 2 or 3) on the corrosion of mild steel in perchloric acid solution <2002MI197>. The inhibition efficiency was structure dependent and the 3-pyridyl gave better inhibition than the 2-pyridyl. X-ray photoelectron spectroscopy helped establish the 3-pyridyl thiadiazoles mode of action toward corrosion. Adsorption of the 3-pyridyl on the mild steel surface in 1M HCIO4 follows the Langmuir adsorption isotherm model and the surface analysis showed corrosion inhibition by the 3-pyridyl derivative is due to the formation of chemisorbed film on the steel surface. 

Recently, Malpass et al. reported a synthesis of epibatidine isomers also under reductive Heck conditions [134, 135]. 2-Azabicyclo[2.2.1]heptene 167 was assembled by cycloaddition of an iminium salt with cyclopentadiene. Treatment of 167 with 2-chloro-5-iodopyridine provided a mixture of exo-5-(6-chloro-3-pyridyl) derivative 168 and exo-6-(6-chloro-3-pyridyl) derivative 169. 

Tobacco use is primarily due to psychopharmacological effects of nicotine (Henningfleld et al. 2006). Nicotine is a tobacco alkaloid, a basic substance that contains a cychc nitrogenous nucleus. In Nicotiana plants, most alkaloids are 3-pyridyl derivatives In cured leaf of Maryland Robinson Medium Broadleaf, 24 pyridine derivatives were identified, including nicotine, nomicotine, anabasine, oxynicotine, myosmine, 3-acetylpyridine, 2,3 -dipyridyl, iticotinamide, anatabine, nicotinic acid, and unidentified pyridine alkaloids of derivatives thereof (Tso 1990). Nicotine is the principal alkaloid in commercial tobacco (this was confirmed in 34 out of 65 Nicotiana species) nomicotine, rather than nicotine, appears to be the main alkaloid in 19 out of 65 species and anabasine is the third most important. In addition to the above-mentioned principal and minor alkaloids, the presence of many trace amounts of new alkaloids or their derivatives were frequently reported, including, for example, 2.4 -dipyridyl, 4,4 -dipyridyl, N -formylanabasine, A -formylanatabine, N -acetylanatabine, N -hexanoyl-nomicotine, N -octanoyl-nomicotine, T-(6-hydroxyoctanoyl) nomicotine, and l -(7-hydroxyoctanoyl) nor-nicotine. 

For the 3-pyridyl derivative 62 (R = 3-Py), it was demonstrated [83ACS(B)617] that the open-chain tautomer 62A or its form protonated on the pyridine nitrogen predominates at high and low solution pH, whereas the equilibrium concentration of the pyrrolinium ion 62C reaches a maximum (53%) at pH 7. The covalent hydrations of compound 62 (R = 3-Py) and 3,4,5,6-tetrahydro-2,3 -bipyridine (anabaseine) were more thoroughly investigated by Zoltewicz (89JOC4462) and all equilibrium constants were measured. 

The photochemical conversion of ( )-l-(3-indolyl)-2-(pyridyl)ethylenes into their Z isomers is followed by photocyclization. Single products are obtained from the 2- and 4-pyridyl compounds, but the two expected isomeric products are obtained from the 3-pyridyl derivatives. Oxidation of the cyclized products yields the fully aromatized systems (75JHC455, 80T1209). 

Tobacco aBaloMa. Collective name for alkaloids of tobacco plants (genus Nicotiana, Solanaceae). Structure occurrence All T. a. contain a pyridine ring they are therefore also occasionally known as pyridine alkaloids. Almost all T. a. are 3-pyridyl derivatives, the main alkaloid is nicotine which is accompanied by a series of minor alkaloids such as nor-nicotine, "anabasine, cotinine, nicotyrine, and nic-otelline (CijHnNj, Mr 233.27, mp. 147-148°C, see figure). Their occurrence is typical for the genus Ni-... 

A listing of the tobacco alkaloids is well beyond the scope of this chapter (see Chaps. 7 and 8) and would serve no useful purpose in the context of the present topic. Several reviews and historical surveys are cited for the interested reader (Kuhn 1965 Pailer 1965 Wynder and Hoffmann 1967 Stedman 1968 Leete 1983). In this chapter, all discussion will be restricted to the most abundant pyridine alkaloids in tobacco and selected 3-pyridyl derivatives formed on combustion. 

Figure 7.11 Hydrogen bonding patterns in C-terminal amides of 2-pyridyl (a and b) and 3-pyridyl derivatives (c-f)...

R = 4-pyridyl, retain the threefold molecular symmetry and assemble their respective molecules via N-H... N hydrogen bonds [29a, b]. The 3-pyridyl or 4-pyridyl functionalities in these derivatives interfere in amide-to-amide hydrogen bonds (Figure 7.23). The N-H... N hydrogen bond aggregation generates a honeycomb network with channels. These channels in 20 were shown to be porous and display desorption of MeOH and absorption of water at room temperature. Later, it was found that the 3-pyridyl derivative 20 indeed crystallizes in three crystalline forms (A, B and C) from the same solvent (MeOH) [29c]. The crystallization process was shown to be dependent on the concentration and evaporation rates. Highly concentrated solution resulted in form A, moderately concentrated solution resulted in form B and dilute solutions resulted in form C. 

To clarify the opposite course of the reaction of the silyl dienol ether 19 with the N-galactosyl imines 16a,d,f on the one hand and the 3-pyridyl derivative 16e on... 

The very effective stereoselection, which is the diastereofacial differentiation occuring during the initial Mannich reaction, can be rationalized by the complexing and chiral properties of the carbohydrate templates. The opposite, but in both cases excellent, stereoselection found for the imines 16a-d,f on the one hand and the 3-pyridyl derivative 16e on the other, is due to the different push-pull activation of the reaction components as is illustrated in the Formulas B and C. The push... 

We have demonstrated a practical synthetic route for the preparation of 2-pyridyl and 3-pyridyl derivatives. It has been accomplished by utilizing a simple coupling reaction of readily available 2-pyridylzinc bromides and 3-pyridylzinc bromides, which were prepared via the direct insertion of active zinc to the corresponding bromopyridines, or they can be purchased (Rieke... 

Mel, CH3CN morpholine or diethylamine, methanol, 76-95% yield. These conditions also cleave tlie 4 -pyridyl derivative. The Pet ester is stable to the acidic conditions required to remove the BOC and r-butyl ester groups, to the basic conditions required to remove the Fmoc and Fm groups, and to hydrogenolysis. It is not recommended for use in peptides that contain methionine or histidine since these are susceptible to alkylation with methyl iodide. 

Mel, CH3CN morpholine or diethylamine, methanol, 76-95% yield. These conditions also cleave the 4 -pyridyl derivative." ... 

Reaction of 10-bromo-iV,l,3-trimethyl-7-oxo-2,3-dihydro-7//-pyrido [ 1,2,3-i/e]quinoxaline-6-carboxamide with 2,6-dimethyl-4-(tributylstannyl)-pyridine in the presence of (Ph3P)2Pd(II)Cl in boiling toluene gave 10-(2,6-dimethyl-4-pyridyl) derivative (OOMIPIO). 

Recently, it has been reported that methyl 2-pyridyl sulphoxides (10) and related pyridyl derivatives (11) (see Schepie 25) are good phase transfer catalysts for SN2 reactions of various primary or secondary alkyl halides in a two-phase reaction system and for the alkylation of phenylacetonitrile or phenylacetone with alkyl halides in liquid-liquid two-... 

Blue luminescence of zinc complexes of pyridyl-containing complexes is an area of current interest.277 Design of blue luminescent materials is of relevance to display applications, as blue-light-emitting diodes, and to this end Che examined solution luminescence of zinc pyridylamine complexes.73,278 Che and co-workers studied the complex Zn40(7-azaindoyl)6 which has a blue emission at 433 nm in the solid state.279,280 In an attempt to improve on stability Wang et al. examined compounds with neutral 7-azaindole and an A-functionalized pyridyl derivative.281 In contrast with other metal complexes of the neutral 7-azaindole (32), Zn(7-azaindole)2(OAc)2 is a blue luminescent compound and a A-(2-pyridyl) 2-azaindole (33) and its complexes were also... 

De Fonseca stated that 1,8-naphthyridine (1003) was obtained not only from /V-(6-methyl-2-pyridyl)aminomethylenemalonate (1001, R = Me, R1 = H), but also from 2-pyridylaminomethylenemalonate (1001, R = R1 = H) by thermal cyclization in diethyl phthalate at 280°C (78MI1). This statement seems to be in opposition to the results of earlier investigations, where only pyrido[ 1,2-a]pyrimidine-3-carboxylate (1002, R = R1 = H) was obtained from the 2-pyridyl derivative (1001, R = R1 = H) under thermal conditions [52JA5491 77GEP2648770, 77JCS(P1)789]. 

Relative Reactivity of Pyridyl Derivatives in Nucleophilic Aromatic Substitutions... 

The cobalt-catalyzed synthesis is also applicable to bifunctional nitriles [Eq.(20)]. The starting materials containing different bridging groups afford the bis(2-pyridyl) derivatives. The reaction proceeds stepwise in the... 

The proposed mechanism is consistent with the experimental results obtained so far. For instance the effects of cation size and -coordination are readily understood in terms of the chelated complex [10a] as is the absence of stereoselectivity in the case of the corresponding 4-pyridyl derivatives where coordination with cation in the manner shown above is impossible. The similarity between vinyl addition and methylation stereochemistry is likewise consistent with the proposed mechanism. Thus it is the equilibrium between [10] and [11] that is primarily responsible for the observed stereochemistry. Work on the stereochemistry of other electrophylic reactions of [2a] is in progress. 

In comparison with the structurally similar 2-pyridyl derivatives this series of ligands can be more easily prepared and offer chelating positions with a more open bite angle, a feature that could influence both the stability of the derivatives formed and their structural framework. 

Formation constants for 1 1 and 2 1 Ag1 complexes with ethylenediamine Schiff bases of the type RCH=NCH2CH2N=CHR, have been reported (Table 53).392 Based on the higher stability of the pyridyl derivative, it was claimed that the pyridyl N participated in the coordination. 

Related to the mechanism of the above structure is the ring-chain-ring isomerization of 3-(2-pyridyl)-[l, 2,3 triazolo 1,5-zz pyrid-7-yl derivatives (139) into 6- 11, 2,3]triazolo 1,5-a ]pyrid-3-yl ] -2-pyridyl derivatives (141) via a diazo compound 140 [139],... 

---