Pyridine 2,6-diacetyl

When pyridine is treated with zinc dust and acetic anhydride, a type of reductive coupling occurs and the product is diacetyltetrahydrodipyridyl (I) this undergoes a curious change on heating yielding pyridine and a new diacetyl compound, 1 4 diacetyl 1 4-dihydropyridine (II). The latter is reduced by zinc and acetic acid to 4-ethylpyridine (III). 

Pyridine, 6-cyano-l,2-dihydro-thermal dimerization, 2, 370 Pyridine, 2-cyanomethyl-tautomerism, 2, 159 Pyridine, 4-cyanomethyl-tautomerism, 2, 159 Pyridine, 2-cyano-2,3,4,5-tetrahydro-metallation, 2, 387 Pyridine, 2,5-diacetyl-ipso substitution, 2, 301 Pyridine, 3,5-diacetyl-l,4-dihydro-Hantzsch synthesis, 2, 482 Pyridine, 4-dialkylamino-as acylation catalysts, 2, 34 Pyridine, 2,2-dialkyl-l,2-dihydro-... 

The A-monoacetyl derivative is formed from acetic anhydride and pyridine at 100° higher temperatures give the 7V,A-diacetyl compound which does not react with peracid. In either case, there is a complete shift of the double bond from C-20(22) to C-17(20), with no evidence for any C-20(21) olefin. 

Another route is described in U.S. Patent 3,345,365 A mixture containing 10 grams of orthoanilamide, 10 cc of pyridine and 20 cc of acetic anhydride is heated for 3 hours at 50°-60°C and allowed to stand overnight. The solids obtained are filtered and crystallized from ethanol to yield 10.73 grams of N,N -diacetyl-o-anilamide, MP 199°-200°C. 

It is probably of importance to the condensation that 2,6-diacetyl-pyridine incorporates a good donor (the pyridine nitrogen) between the... 

As in the case of 2,2 -bipyridine, the most important synthetic routes to 4,4 -bipyridine use pyridine as starting material. One method of synthesizing 4,4 -bipyridine from pyridine was discovered by Dimroth in 1921. If pyridine in acetic anhydride is treated with zinc dust, l,l -diacetyl-l,r,4,4 -tetrahydro-4,4 -bipyridine is formed. This compound is readily oxidized and hydrolyzed by moist air to 4,4 -bipyridine. Various oxidizing agents assist in the conversion to 4,4 -bipyridine. By-products from the reaction include 1,1 -diacetyl-l,T-dihydro-4,4 -bipyridine. This method of synthesizing 4,4 -bi-pyridine has frequently been used. ° The reduction of pyridine in acetic anhydride by catalytic hydrogenation instead of by zinc dust is less satisfactory because of the formation of other reduction products. Several variations and improvements in the Dimroth reaction have subsequently... 

Jager, B.V., and Stagg, G.N. Toxicity of diacetyl monoxime and of pyridine-2-aldoxime methiodide in man. Bull. Johns Hopkins Hosp. 102 203-211, 1958. 

The 3-amino-5,7-dimethylpyrimido[4,5-( ]-l,2,4-triazine 93 (Equation 13) undergoes acetylation with acetic anhydride in pyridine to give the mono-acetylated analogue 94 together with a small amount (9%) of the corresponding diacetylated derivative <2001JHC141>. 

H h3c n. ch3 1 1 R1-0C Y C0-R1 A R U Rl CH3 och3 R2 H o-chf3 NaNQ3 n2so. -8 0,3 3,5-Diacetyl-2,6- dimethyl-4-(4- nitro-phenyll- 1.4- dihydro-pyridin 4- 2-Difluormethoxy- 4-nitro-phenyl)- 3.5- dimethoxy-carbonyl-2,6-dimethyl-.. . 56-72 4... 

Figure 5. Profiles of volatiles for low-quality peanuts with contaminants, raw and roasted (I) ethanol (2) pentane (3) 2-propanol (4) acetone (5) methylene chloride (6) methyl acetate (7) 2-methylpropanal (8) chloroform (9) diacetyl (10) benzene (11) 3-methylbutanal (12) 2-methylbutanal (13) 2,3-pentanedione (14) fl-methyl-pyrrole (15) pyridine (16) toluene (17) hexanal (18) 2-methylpyrazine (19) 2-methylpyrrole (20) 2-heptanone (21) styrene (22) 2,5-dimethylpyrazine (23) 2-ethyl-5-methylpyrazine (24) 2-ethyl-3,6-dimethylpyrazine (25) phenylacetalde-hyde.

The oxidation of AT-acetylthiourea in pyridine by hydrogen peroxide to the diacetyl derivative of 3,5-diamino-l,2,4-thiadiazole (12, R = AcNH) (in 35% yield)27 may also be included under this general heading. 

Colourless crystals soluble in alcohol M.P. 159° (J. C. S., loc. tit.) M.P. 164-2° (Am. Soc., 13, 556). Oxidised with chromium trioxide in glacial acetic acid solution, yields anthxaquinone gives a diacetyl derivative on heating with acetic anhydride and pyridine (J. C. S., 117, 1335). 

Highly substituted pyridinium salts of type 1 are easily accessible by Hantzsch-type synthesis. They are valuable products in that they can often be transformed easily into otherwise difficultly accessible, highly substituted benzenes or pyridines by base-catalysed rearrangement. For example, treatment of the salt 2 with ethanolic sodium hydroxide at room temperature for one hour gives 2,4-diacetyl-lV,5-dimethylaniline 3 in 85% yield, while 3-acetyl-5-cyano-6-methyl-2-methylamino-4-phenylpyridine 5 is obtained in 88% yield from the salt 4 under the same conditions. 

On treatment with acetic anhydride in pyridine, the yellow tetraketone (68), the yellow triketone (66), and the diketone (67) afforded monoacetyl, diacetyl, and triacetyl derivatives, respectively. All these derivatives contained a tertiary acetoxyl group. However, comparisons of 1H-NMR spectra of the parent ketones with those of the acetyl derivatives indicated that a rearrangement of the molecule or a major conformational change must have occurred. On the basis of extensive H-NMR spectral analysis, structure 69 was proposed for the diacetyl derivative which was derived from the triketone 66. Structure 69 was justified on the basis of conformational arguments. 

Figure 28 shows another two examples of trivalent Schiff base ligands. The macrocyclic ligand was generated in a template condensation of 2,6-diacetyl-pyridine with l,3-diamino-2-hydroxypropane in the presence of lanthanide salts [187]. The La(N03)3 H20-reaction yielded a trinuclear complex of composition [La3U/ 3-0HX0H)(N03)4]-7H20 [188]. 

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