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4-pyridyl position

Scheme 12 Use of 4-pyridyl position as means of supporting 1 to give 39... Scheme 12 Use of 4-pyridyl position as means of supporting 1 to give 39...
The 5-position is the preferred site for sulfonation (58. 392). This position is more reactive than any of the pyridine ring in. V-[pyridyl-(2)]-thiazolyl-(2)-amine (178) (132, 382, 383). [Pg.75]

These halogenation reactions all take place in the 5-position (408. 409. 430) even when there is a phenyl or a 2-pyridyl (382) substituent on the exocyclic nitrogen. Crystalline perbromides have been isolated (166. 320. [Pg.77]

Treating 5.5 g of 2-amino-4,5-dimethylthiazole HCl with 0.66 g of solid sodium hydroxide 15 min at 220°C yields 53% of 4.4. 5.5 -tetramethyT 2,2 -dithiazolylamine, whose structure w as proved by identification with the produa obtained from the reaction between dithiobiuret and 3-bromo-2-butanone (467). This result is comparable to the reaction between 2-aminopyridine and its hydrochloride to yield bis(pyridyl-2)amine (468). Gronowitz applied this reaction to 2-aminothiazole, refluxing it with its hydrochloride 4 hr in benzene and obtained the dimeric 2-aminothiazole (236). He proposed a mechanism (Scheme 143) that involves the addition of a proton to the 5-position of the ring to give 234. The carbocation formed then reacts on the 5-position of a second... [Pg.85]

Nucleophilic reactivity of the sulfur atom has received most attention. When neutral or very acidic medium is used, the nucleophilic reactivity occurs through the exocyclic sulfur atom. Kinetic studies (110) measure this nucleophilicity- towards methyl iodide for various 3-methyl-A-4-thiazoline-2-thiones. Rate constants are 200 times greater for these compounds than for the isomeric 2-(methylthio)thiazole. Thus 3-(2-pyridyl)-A-4-thiazoline-2-thione reacts at sulfur with methyl iodide (111). Methyl substitution on the ring doubles the rate constant. This high reactivity at sulfur means that, even when an amino (112, 113) or imino group (114) occupies the 5-position of the ring, alkylation takes place on sulfiu. For the same reason, 2-acetonyi derivatives are sometimes observed as by-products in the heterocyclization reaction of dithiocarba-mates with a-haloketones (115, 116). [Pg.391]

Syntheses of Nicotine. Pictet and Cr pieux found that 3-aminopyridine mueate on dry distillation yielded l-(3-pyridyl)pyrrole (I), and this, in accordance with the usual behaviour of such pyrrole derivatives, transfers its pyridyl substituent from the 1- to the 2-position at a red heat giving 2-(3-pyridyl)pyrrole (II), which is nomieotyrine. The potassium derivative of this reacts with methyl iodide to form l-methjd-2-(3-pyridyl)-pyrrole methiodide, which is identical with nieotyrine methiodide (III), and on distillation with lime yields nieotyrine (IV Cl — CH). For a re-investigation of this synthesis see Spath and Kainrath. ... [Pg.40]

When in position 2 on a 2-pyridyl or 2-furyl ring, 4,9-oxo groups can be reduced and acylated the obtained compounds were active against streptococci and staphylococci (62GEP1). [Pg.213]

Bromoquinolines behave in the Suzuki reaction similarly to simple carbocyclic aryl bromides and the reaction is straightforward. Examples include 3-(3-pyridyl)quinoline (72) from 3-bromoquinoline (70) and 3-pyridylboronic acid (71) (91JOC6787) and 3-phenyl-quinoline 75 from substituted 3,7-dibromoquinoline 73 and (2-pivaloylaminophenyl)boronic acid 74 (95SC4011). Notice that the combination of potassium carbonate and ethanol resulted in debromination at the C(7) position (but the... [Pg.13]

Highly c/s-selectivity and low molecular weight distribution polymerization of l -butadiene with cobalt(II) pyridyl bis(imine) complexes in the presence of ethylaluminum sesquischloride effect of methyl position in the ligand... [Pg.873]

When the donor group is attached at a /3-pyrrole position rather than the meso position, the properties of the assemblies change. Knapp (57) synthesized a series of /3-pyrrole 2-pyridyl substituted zinc porphyrins (49, Fig. 16) and showed that dimerization takes place provided the meso-substituents are not too bulky H NMR and VPO measurements showed that the porphyrin, which bears heptyl substituents, dimerizes in solution, whereas the phenyl analog does not. The complexation-induced changes in chemical shift suggest a stacked structure for the dimer. [Pg.235]

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... [Pg.241]

A polymeric structure can be generated by intermolecular coordination of a metalloporphyrin equipped with a suitable ligand. Fleischer (18,90) solved the crystal structure of a zinc porphyrin with one 4-pyridyl group attached at the meso position. In the solid state, a coordination polymer is formed (75, Fig. 30). The authors reported that the open polymer persists in solution, but the association constant of 3 x 104 M 1 is rather high, and it seems more likely, in the light of later work on closed macrocycles (see above), that this system forms a cyclic tetramer at 10-3 M concentrations in solution (71,73). [Pg.249]

Irreversible inhibition is probably due to the alkylation of a histidine residue.43 Chymotrypsin is selectively inactivated with no or poor inhibition of human leukocyte elastase (HLE) with a major difference the inactivation of HLE is transient.42,43 The calculated intrinsic reactivity of the coumarin derivatives, using a model of a nucleophilic reaction between the ligand and the methanol-water pair, indicates that the inhibitor potency cannot be explained solely by differences in the reactivity of the lactonic carbonyl group toward the nucleophilic attack 43 Studies on pyridyl esters of 6-(chloromethyl)-2-oxo-2//-1 -benzopyran-3-carboxylic acid (5 and 6, Fig. 11.5) and related structures having various substituents at the 6-position (7, Fig. 11.5) revealed that compounds 5 and 6 are powerful inhibitors of human leukocyte elastase and a-chymotrypsin thrombin is inhibited in some cases whereas trypsin is not inhibited.21... [Pg.365]


See other pages where 4-pyridyl position is mentioned: [Pg.341]    [Pg.121]    [Pg.52]    [Pg.78]    [Pg.341]    [Pg.121]    [Pg.52]    [Pg.806]    [Pg.78]    [Pg.139]    [Pg.183]    [Pg.43]    [Pg.444]    [Pg.244]    [Pg.179]    [Pg.290]    [Pg.291]    [Pg.303]    [Pg.30]    [Pg.55]    [Pg.161]    [Pg.101]    [Pg.141]    [Pg.306]    [Pg.418]    [Pg.85]    [Pg.873]    [Pg.204]    [Pg.212]    [Pg.5]    [Pg.14]    [Pg.13]    [Pg.217]    [Pg.233]    [Pg.240]    [Pg.241]    [Pg.255]   
See also in sourсe #XX -- [ Pg.134 ]




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Pyridyls

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