Pyridine Homologues

Andon, R.J.L., Cox, J.D. (1952) Phase relationships in pyridine series. Part I. The miscibility of some pyridine homologues with water. J. Chem. Soc. 4601 -606. 

Trans. Faraday Soc. 53, 410-26 (1957). Vapor-liquid composition AF, AH mixing, pyridine, homologues in H2O, 70-90 C. 

S3mthesis of Collidine.—The most important synthesis of pyridine homologues is that of collidine from which pyridine may be obtained by elimination of the methyl groups by oxidation and loss of carbon dioxide. When aldehyde ammonia is heated with aceto-acetic ester a derivative of a di-hydrogenated collidine is obtained, as follows ... 

Like pyridine, pyridine homologues and derivatives are converted into amine oxides. a-Picoline oxide is prepared by oxidation with hydrogen peroxide in acetic acid in 83% yield [1188]. Under identical conditions, 2,5-dimethylpyridine oxide and nicotinamide oxide are obtained in 84% yield [160] and 73-82% yield [162], respectively. Pentachloropyridine is oxidized to its oxide by peroxyacetic or peroxytrifluoroacetic acid (equation 504) [755]. 

As well as the reactions discussed above, there are recorded several less well defined which probably involve similar processesi208-ii Thus, pyridine, sodium hydroxide and chloroform (and related compounds) quickly produce an intense red colour io. Dichlorocarbene may be involved. Pyridine homologues give isonitriles of the benzene series under these conditionsi n. The pyridine-bisulphite compound mentioned above (p. 249) yields glutacon-dialdehyde dianil with caustic soda and anilinei2i2 ... 

To 2,A. Electrophilic Substitutiori] Bromination of pyridine homologues in fuming sulphuric acid gives excellent yields of 3-bromopyridinesi24i,... 

It has been mentioned ( 4.4.2) that nitronium tetraffuoroborate reaets with pyridine to give i-nitropyridinium tetraffuoroborate. This compound and several of its derivatives have been used to effect what is called the transfer nitration ofbenzeneandtoluene. i-Nitropyridinium tetraffuoroborate is only sparingly soluble in acetonitrile, but its homologues are quite soluble and ean be used without isolation from the solution in which they are prepared. i-Nitropyridinium tetra-fluoroborate did nitrate toluene in boiling aeetonitrile slowly, but not at 25 In eontrast, i-nitro-2-pieolinium tetraffuoroborate readily... 

Tosylates of pentaerythritol and the higher homologues can be converted to their corresponding tetra-, hexa-, or octaazides by direct reaction of sodium azide (36), and azidobenzoates of trimethyl olpropane and dipentaerythritol are prepared by reaction of azidobenzoyl chloride and the alcohols in pyridine medium (37). 

When yohimbine is heated with potash solution it is eonverted into potassium yohimbate, from which yohimbic acid (the forms yohimboie and yohimboaic are also used and noryohimbine), C20H24O3N2. H2O, is liberated by acetie acid it crystallises from water in lustrous prisms, m.p. 269° or 299° (dry, dec.), [ajo 138-8° (pyridine), and, on esterification with methyl alcohol and its homologues, reproduces yohimbine and its homologues, analysis of which by Field confirmed the view that yohimbine is methyl yohimbate, and has the formula assigned to it by Fourneau and Page. ... 

In quinoline and isoquinoline, the benzene ring is more receptive to fluorma-tion, its double bonds being saturated and the hydrogen atoms replaced in preference to those in the pyridine ring As with pyridine and its homologues, ring contraction takes place during fluorination with cesium tetrafluorocobaltate at... 

Dihydro- and 1,4-dihydro derivatives are formed as intermediates in the reduction of quaternary pyridine salts and their homologues with sodium borohydride or formic acid. A proton is added to the present enamine grouping and the formed immonium salts are reduced to the l-methyl-l,2,5,6-tetrahydropyridine derivatives (157) and to completely saturated compounds (158) (254) (Scheme 14). 

The following n/m values were obtained for the degrees of association n at molal concentration m, measured in ammonia by cryoscopy. Lithium phenolate (255a, 2.21 0.20/0.1530) is nearly dimeric in ammonia, while in pyridine and dioxolane it is tetrameric, as shown by vapor pressure and NMR measurements. The 2,6-dimethyl homologue (255b)... 

In order to study the effect of substituents near the hydrolyzable bond, four fatty acid ethoxylates with different degrees of steric hindrance near the ester bond, see Fig. 4, have been synthesized [18]. The homologue pure surfactants were prepared by reacting the appropriate acid chlorides with a large excess of tetra(ethylene glycol) in the presence of pyridine. 

Pyridine and its homologues are produced in coking procedures and present in the non-condensable gases. Pyridine is also present in coal-tar and as a component in creosote (Agency for Toxic Substances Disease Registry, 1992 Dutch Ministry of Social Affairs and Employment, 1993). 

Strong bases have an adverse effect on the stability of smokeless powder as described above. Moreover, Angeli [59] found that pyridine and its homologues cause decomposition of nitrocellulose. (On the action of pyridine on other nitric esters see Yol. II.) At an elevated temperature (e.g. 110°C) pyridine can produce an intense denitration of esters which may even lead to an explosion. 

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