3- Acetyl-2,6-dimethyl-5- pyridine

N-silylated imines 509 react with the Li salts of tosylmethylisonitriles to give 4,5-disubstituted imidazoles in moderate yields [93]. Acetylation of N-trimethylsilyl imines 509 with acetyl chloride and triethylamine affords 72-80% of the aza-dienes 510 these undergo readily Diels-Alder reactions, e.g. with maleic anhydride at 24 °C to give 511 [94] or with dimethyl acetylenedicarboxylate to give dimethyl pyridine-3,4-dicarboxylates [94] (Scheme 5.29). 

Omeprazole is obtained [15] by the reaction of acetyl ethyl propionate 1 with ammonia to give ethyl -3-amino-2,3-dimethyl acrylate 2. Compound 2 was converted to to 2,4-dihydroxy-3,5,6-trimethyl pyridine 3 by treatment with methyl diethylmalonate. Treatment of compound 3 with phosphorous oxychloride produced 2,4-dichloro-3,5/6-trimethyl pyridine 4. 4-Chloro-3/5,6-trimethyl pyridine 5 was obtained by treatment of compound 4 with hydrogen. On treatment of compound 5 with hydrogen peroxide and acetic acid, 4-chloro-3,5,6-trimethyl-pyridine-N-oxide 6 was produced. Treatment of compound 6 with acetic anhydride gave 4-chloro-2-hydroxymethyl-3,5-dimethyl pyridine 7 which was converted to 2-hydroxymethyl-3,5-dimethyl-4-methoxypyridine 8 by treatment with sodium methoxide. Compound 8 was treated with thionyl chloride to produce 2-chloromethyl-3,5-dimethyl-4-methoxypyridinc 9. Compound 9 interacts with 5-methoxy-2-mercaptobenzimidazole to give 5-methoxy 2-[((4-methoxy-3,5-dimethyl-2-pyridinyl)methyl)thio]-lH-bcnzimidazole 10 which is oxidized to omeprazole 11. 

A like behaviour has been found for the ring C-substituted substrates such as 613, although in the case of hydrolysis, the extent of P—N bond fission is not so great. The alkaline hydrolysis of 613 (X = O, Z = S, A = Me) proceeds with P—O fission to give an unstable intermediate this is first methylated (Mel) to give 621 (Z = S) which is acetylated (Ac20-Pyridine) in order to prevent unwanted intramolecular displacements, and the resultant product 622 is then methanolysed under acid conditions to give 0, S -dimethyl methylphosphonothioate 623 (Z = S) as a 2 3 mixture of R- and iS-enantiomers. The implication is that the endocyclic P—O bond was therefore cleaved with preponderant... 

Chapter V. Quinaldine (V,2) 2-methyl-, 2 5-dimethyl- and 2-acetyl-thiophene (V,8-V,10) 2 5-dimethyl and 2 4-dimethyl-dicarbethoxy-p3nrole (V,12-V,13) 2-amino- and 2 4 dimethyl-thiazole (V,15-V,16) 3 5-dimethyl-pyrazole (V,17) 4-ethylp3rridine (from pyridine) (V,19) n-amyl-pyridines from picolines) (V,28) picolinic, nicotinic and isonicotinic acid (V,21-V,22) (ethyl nicotinate and p-cyanop3n idine (V,23-V,24) uramil (V,25) 4-methyl-(coumarin (V,28) 2-hyi-oxylepidine (V,29). 

Pyridyl)hydrazine (Aldrich), 4-acetylpyridine (Acros), N,N,N -trimethylethylenediamine (Aldrich), methylrhenium trioxide (Aldrich), InQj (Aldrich), Cu(N0j)2-3H20 (Merck), Ni(N03)2-6Il20 (Merck), Yb(OTf)3(Fluka), Sc(OTf)3 (Fluka), 2-(aminomethyl)pyridine (Acros), benzylideneacetone (Aldrich), and chalcone (Aldrich) were of the highest purity available. Borane dimethyl sulfide (2M solution in THE) was obtained from Aldrich. Methyl vinyl ketone was distilled prior to use. Cyclopentadiene was prepared from its dimer immediately before use. (R)-l-acetyl-5-isopropoxy-3-pyrrolin-2-one (4.15) has been kindly provided by Prof H. Hiemstra (University of Amsterdam). 

Pyrrolo[3,4-d]pyridazinium salts, 2,3-dimethyl-synthesis, 4, 291 Pyrrolo[ 1,2-6]pyridazinones oxidation, 4, 298 Pyrrolo[2,3-6]pyridine, 1-acetyl-cycloaddition reactions, 4, 509 Pyrrolo[2,3-6]pyridine, 3-bromo-nitration, 4, 505... 

The presence of the aliphatic amino group complicates the course of the reaction. Thus, the oxidative coupling of 4-ethynyl-1,3-dimethyl-5-aminomethylpyrazole in mild conditions (20°C, CuCl, pyridine, O2) leads to only 20% of butadiyne. However, acylic protection eliminates these complications, and 4-ethynyl-1,3-dimethyl-5-(acetyl)aminomethylpyrazole forms a dehydrodimer in 95% yield (Scheme 66) (86TH1). 

The monoacetate 9a (R1 = Ac) and the diacetate 10a (R1 = R2 = Ac) are obtained by treatment of 8 with acetic anhydride in anhydrous pyridine at room temperature 4 the oxo group in position 5 of 8 is more reactive towards acetylation. Similarly, the S,S-dioxidc of 8 can be converted to the bisacetylated S,5-dioxide of 10a in 78 % yield.74 Methylation of 8 with diazomethane gives 9c (65 % yield), along with 14 % of the 3-methoxy compound 11. Other alkylation agents, such as dimethyl sulfate in the presence of potassium carbonate, selectively give 9c, albeit in lower (30 %) yield.90 The dimethyl enol ether 10c (R1 = R2 = Me) is obtained by a subsequent methylation of 9c (R1 = Me) with dimethyl sulfate and potassium teri-butoxide.90... 

Recently, use of LiCl/DMAc and LiCl/l,3-dimethyl-2-imidazolidinone as solvent systems for acetylation of cellulose by acetic anhydride/pyridine has been compared. A DS of 1.4 was obtained the substituent distribution in the products synthesized in both solvents was found to be the same, with reactivity order Ce > C2 > C3. Therefore, the latter solvent system does not appear to be better than the much less expensive LiCl/DMAc, at least for this reaction. It appears, however, to be especially efficient for etherification reactions [178]. It is possible, however, that the effect of cellulose aggregation is more important for its reaction with the (less reactive) halides than with acid anhydrides this being the reason for the better performance of the latter solvent system in ether formation, since it is more efficient in cellulose dissolution. 

Repeated methylation of bagasse native lignin with dimethyl sulfate yielded a product with a 29-1 % methoxyl content. Four such methyl-ations did not change this value. However, the infrared spectrum of this derivative still revealed a small absorption band at 3400 cm1. Thus, it appeared that at least one hydroxyl group could not be methylated. Treatment of this methylated product with acetic anhydride and pyridine gave an acetate, which did not exhibit an absorption band at 3400 cm-1. Consequently, a tertiary hydroxyl group, which can be acetylated but not methylated, seems to be present in this lignin. 

Pyridine, 3-(dimethyl-pyrryl) Cured Lf Pyridine, 3-acetyl Cured Lf smoke Pyridine, 3-aldehyde Cured Lf " ... 

Several attempts to prepare typical alcohol derivatives of [Cr(HO-A)2]-were unsuccessful these include Schotten-Bauman conditions (acetyl chloride in chloroform shaken with cold, aqueous alkaline solution of complex), refluxing in acetyl chloride, in glacial acetic acid, acetyl chloride in hot dimethyl formamide, acetyl chloride and pyridine in acetonitrile, and acetic anhydride in acetonitrile. The failure of refluxing acetyl chloride to effect acetylation brings to mind the work of Keller and Edwards (4) the acetyl chloride system is completely heterogeneous and consequently not conducive to reaction. However, even the homogeneous reaction of [Cr(HO-A)2] — with acetyl chloride in acetonitrile failed to give a measurable quantity of the diester. 

A. 5-(1-Hydroxyethylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione. A flame-dried, 500-mL, three-necked, round-bottomed flask is equipped with a stir bar, nitrogen inlet adapter, and a pressure-equalizing addition funnel fitted with a rubber septum. The flask is charged with 22.0 g of Meldrum s acid dissolved in 153 mL of methylene chloride, and 24.8 mL of pyridine (Note 1), and the mixture is cooled to -25°C (Note 2). A mixture of 18.3 mL of methylene chloride and 13.1 mL of acetyl chloride is slowly added to the reaction mixture via the addition funnel over 1 hr (Note 3). After the addition of the acetyl chloride is complete, the reaction is slowly warmed over 3 hr to... 

Various indolizines containing vinyl groups in the pyridine ring have been synthesized by standard procedures, e.g., Ref. 212. Turchinovich and co-workers found that whereas 2-methyl-6-vinyl- and 1,2-dimethyl-6-vinylindolizine would not polymerize, even in the presence of an initiator, 3-acetyl-l,2-dimethyl-6-vinylindolizine polymerized spon-... 

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