Pyridines aroyl

Pyridin-2-one, 4-amino-3-cyano-synthesis, 2, 460 Pyridin-2-one, aroyl-synthesis... 

The hydroxy group undergoes 0-acylation and deacylation (79JHC689). These reactions of functionalized hydroxyfurazans are valuable methods for modification of these compounds. Thus, hydroxybifurazan 248 was aroylated with benzoyl chloride in the presence of pyridine with concomitant cleavage of the unsubstituted furazan ring to give nitrile 262 (Scheme 170) (75LA1029). 

Aroyl-pyridine werden mit Titan(III)-chlorid/Lithiumalanat mit bis zu 93% d.Th. zu den entsprechenden Alkoholen reduziert. Als Nebenprodukt fallen dimere Verbindungen an z.B.5 ... 

The 1,4-diketone 1,2-dibenzoylethane 151 can be transformed in one step into 3,4-dibenzoyl-l,2,5-thiadiazole 152 when treated either with preformed trithiazyl trichloride in tetrachloromethane (Equation 29) <1997J(P1)2831> or with urethane, thionyl chloride, and pyridine in benzene (Katz reagent) <2002ARK90> (see also Section 5.09.9.2.l(iii)(b)). Similarly, treatment of 1,3-diketones 153 with tetrasulfur tetranitride antimony pentachloride complex in toluene at 100 °C < 1998J(P 1 )2175 >, or trithiazyl trichloride in boiling tetrachloromethane < 1997J(P 1)2831 >, affords 4-substituted-3-aroyl-l,2,5-thiadiazoles 154 (Equation 30). 

Heating to reflux a pyridine solution of 3-substituted-5-(l-aroyl-l-bromo)methylthio-4-phenylamino-4//-[l,2,4]tria-zoles 81 (available from the corresponding 1,2,4-triazoles with phenacyl bromides and subsequent ultraviolet (UV) light-induced bromination) affords 3-substituted-6-aroyl-5,6-dihydro-5-phenyl[l,2,4]triazolo[3,4-6][l,3,4]thiadiazoles 82 (Equation 19) <1993IJH135>. 

A recent method for the synthesis of the indolizine skeleton is represented by a three-component reaction between a-bromo ketones 16, pyridine 17, and ethyl propiolate or diethyl acetylenedicarboxylate. These three reagents, under microwave irradiation and catalysis by basic alumina, afforded a good variety of 3-aroyl indolizines 18 <20030L435> (Scheme 4). 

As CH-acids in the MCRs with aldehydes and aminoazoles, other classes of organic compounds were used as well. Cyanoacetic acid derivatives, acetoyl(aroyl) acetonitriles, ketosulfones, acetophenones, and other reagents were successfully introduced into these three-component heterocyclizations. For example, synthesis of pyrazolo[3,4-b]pyridine-5-carbonitriles 40 was carried out as the multicomponent treatment of 5-aminopyrazole, aldehyde, and benzoylacetonitriles solvent-free by fusion either in ammonium acetate at 120°C or in boiling ethanol with EtsN (Scheme 17) [69]. The second approach gave the worst results from the viewpoint of yields and purity of the target compounds. 

Zinc chloride-doped natural phosphate was shown to have catalytic behavior in the 1,3-dipolar cycloadditions of nucleoside acetylenes with azides to form triazolonucleosides <99SC1057>. A soluble polymer-supported 1,3-dipolar cycloaddition of carbohydrate-derived 1,2,3-triazoles has been reported <99H(51)1807>. 2-Styrylchromones and sodium azide were employed in the synthesis of 4(5)-aryl-5(4)-(2-chromonyl)-1,2,3-triazoles <99H(51)481>. Lead(IV) acetate oxidation of mixed bis-aroyl hydrazones of biacetyl led to l-(a-aroyloxyarylideneamino)-3,5-dimethyl-l,2,3-triazoles <99H(51)599>. Reaction of 1-amino-3-methylbenzimidazolium chloride with lead(fV) acetate afforded l-methyl-l/f-benzotriazole <99BML961>. Hydrogenation reactions of some [l,2,3]triazolo[l,5-a]pyridines, [l,2,3]triazolo[l,5-a]quinolines, and [l,2,3]triazolo[l,5-a]isoquinolines were studied <99T12881>. 

Sodium borohydride is the reagent of choice for the reduction of the pyridine ring in isoquinolinium salts. It reacts so rapidly that even the carbonyl group of a 1-aroyl substituent can survive (equation 154) (63JCS2487). A 1,2-dihydro intermediate has been isolated during the cyclization of (253) to 2,3-dimethoxyberbine by sodium borohydride, which suggests that a similar mechanism to that described above is operative here (equation 155) (60JOC90). 

An interesting variant uses acyl- or aroyl-methylpyridinium salts with ammonia or an amine to produce dipyridiniumdihydropyridine salts (655). With aromatic aldehydes the dihydropyridines are produced directly or the intermediate (654) can be isolated and subsequently treated with perchloric acid (75LA849). With formaldehyde (giving dihydropyridines without a substituent in position 4), the 1,5-diketone can be isolated and cyclized by ammonia (75LA864). The dipyridinium salts (655) undergo some useful transformations they can be oxidized to pyridines (656), and these dipyridinium pyridine salts give... 

Tetrahydropyrrolo[4,3-. ]pyridines can be synthesized from 5,5-dimethyltetramic acid, 84, in a sequence of steps that begins with aryl aldehydes to generate arylmethylene-substituted tetramic acids. A Michael reaction with methyl acetoacetate followed by treatment with ammonium acetate yields the tetrahydropyrrolopyridine derivatives (Scheme 20) <2005H(65)377>. A similar reaction can be carried out with aroyl-substituted butenolides to give substituted furopyridine derivatives. 

Kohlcnsaure-(2-aroyl-hydrazid)-dialkylamide Man lost 0,03 mol Aroyl-hydrazin in 15 ml Pyridin untcr schwachem Erwarmen und fugt dann 0,033 mol N,N-Dialkyl-carbamidsaure-chlorid hinzu. Nach 12 h Stehen fallt man mit Wasscr die Semicarbazide aus, wiischt mil Wasser und trocknet. 

A useful practical method for the preparation of aroyl fluorides 1 and arenesulfonyl fluorides 2 by reaction of the zinc(II) fluoride/pyridine system with the corresponding chlorides has been described.50 Replacement of zinc(II) fluoride by potassium fluoride, or of pyridine by other tertiary amines (Et3N or l-methylpiperidin-2-one) or by other solvents (DMSO, DMF, MeCN, or THF) did not give satisfactory results. The exclusive effectiveness of pyridine is presumably due to its ability to weaken the Zn — F linkage by appropriate coordination to the zinc atom.50... 

To a solution of ZnF2 (0.03 mol) in pyridine (30 mL) was added the aroyl chloride or the arenesulfonyl chloride (0.03 mol) with stirring at 25 °C. Stirring was continued until the reaction was complete (checked by 19F NMR spectroscopy) then treated by either Method A or B as follows. 

The only collection of UV spectral data for derivatives of compound 1 show the effect of a 3-acyl or 3-aroyl substituent.23 A bathochromic shift of the longest wavelength absorption band can reach 20 nm with an aroyl substituent. The spectra of 2-phenyl-,1" 2-benzyl-, 2-benzoyl-, and 2-benzhydryl[l,2,4]triazolo[l,5-fl]pyridines,42 and of the mesoionic compounds 42-44,56 and 109200 are reported. On the triazolopyridine 3, substitu-... 

Pyrazolo[4,3-b]pyridine 181 (R1 = H,R2 = Me) in refluxing pyridine was acylated and tosylated in the 1-position. Milder conditions afforded either a 2-acyl or a mixture of 1- and 2-aroyl derivatives, suggesting a possible equilibrium between the two products.111... 

A simple two-step synthesis of 4-arylthieno[3,2-c]pyridine-6-carboxylic acids has recently been presented by Eweiss (Scheme 74) (B-81MI31703). The condensation of thiophene-2-carbaldehyde with an N -aroylated a-amino acid yields a thienylidene azlactone (281) which on treatment with AICI3 is converted to a thieno[3,2-c]pyridine (283). A nitrilium ion (282) resulting from a vinyl-oxygen fission is probably involved as an intermediate. Sandberg s method already mentioned in the previous section has also been applied to the synthesis of thieno[3,2-c]pyridines (Scheme 75). 

Table 13 Synthesis of [l,2,5]thia(oxa or selena)diazolo[3,4-c]pyridines (240)-(242) from 3,4-aroyl-[l,2,5]thia...

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