Pyridine phenacyl

Acetonyl-2(l//)-quinoxalinone (231, R = Me) reacted as its tautomer (231a, R = Me) to give 2-chloro-3-(2-chloroprop-l-enyl)quinoxaline (232, R = Me) (POCI3, pyridine, reflux, 10 min 62%) 3-phenacyl-2(l//)-quinoxalinone (231, R = Ph) likewise gave 2-chloro-3-(p-chlorostyryl)quinoxaline (232,... 

Electronic effects. Nucleophilic attack is favoured by electron-withdrawing groups on the amide and the acyloxyl side chains. Interpolated bimolecular rate constants at 308 K for the series of para-substituted /V-acetoxy-/V-butoxybenzamides 25c, 26b-g and 26i (Table 5) gave a weak but positive Hammett correlation with a constants ip = 0.13, r = 0.86).42,43 These Sn2 reactions are analogous to those of aniline and substituted pyridines with phenacyl bromides, which have similar Arrhenius activation energies and entropies of activation in methanol (EA= 14-16 kcal mol-1, AS = — 27 to —31 calK-1 mol-1) and 4-substituted phenacyl halides afforded a similar Hammett correlation with pyridine in methanol (cr, p — 0.25).175... 

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>. 

The most efficient routes to the cationic oxazolo[3,2- ]pyridine ring system 351 rely on the method of Bradsher and Zinn <1967JHC66> involving the cyclocondensation of iV-phenacyl-2-pyridones 349 obtained by alkylation of readily available 2-pyridones 347 (Scheme 95). This method has been used by Babaev et al. to prepare a series of 6-nitro-oxazolo[3,2- ]pyridines 355 from 5-nitro-2-pyridone 352 in excellent yields <2003MOL460>. Similarly, tricyclic oxazolo[3,2- ]pyridines 359 have been prepared from the corresponding quinolin-2(177)-ones 356 <2003H(60)131>. 

Nucleophilic attack by iV-methylaniline is favoured by electron-withdrawing groups on the amide and acyloxyl side chains. A series of / ara-substituted Af-acetoxy-Af-butoxy-benzamides (138) (Table 6) gave a weak but positive Hammett correlation with a constants (p = 0.13, r = 0.86) °. The analogous reactions of pyridine with para-substituted phenacyl halides in methanol afforded a similar Hammett correlation a, p = 0.25) . The bimolecular rate constants for the limited series of Ai-benzoyloxy-A-benzyloxybenzamides (139) in Table 6 correlated strongly with Hammett a constants (p = 1.7, r = 0.97) °. Stabilization of developing carboxylate character supported the computed charge redistribution in the transition state ... 

Milosevic, M., Andjelkovic, D., and Binenfeld, Z. Effets de divers oximes, derives de chlorures de 1-phenyle, 1-benzyle et 1-phenacyle pyridine et les analogues de 4-formyle pyridin dans 1 intoxication au paraoxon. Med. Exp. 10 73-78, 1964. 

Thiophenes can be synthesized from a sequence involving the reaction of activated methylene compounds with carbon disulfide in base. The resulting disulfide salts, without isolation, are reacted with phenacyl bromide to afford highly substituted thiophenes, 78. Compound 78 reacts with ethyl cyanoacetate, malononitrile, or acrylonitrile to afford thieno[3,2-/ ]pyridine derivatives <1995CCC1578>. 

Cyanopyrroles, formed from malononitrile and phenacyl halides, offer another route to the synthesis of pyrrolo[2,3-3]pyridines <2004MI15>. Treatment of the cyanopyrroles with ethyl acetoacetate leads to propenylamino-pyrroles which undergo further cyclization to form highly functionalized pyrtolo[2,3-3]pyridine derivatives. 

Selective oxidation of polymethylpyrimidines. 2,4-Di- and 2,4,6-trimethyl-pyrimidines are selectively oxidized to 4-carboxylic acids by a slight excess of Se02 in pyridine. Yields are about 40-65%. This increased reactivity of a 4-methyl group of polymethylpyrimidines is also observed in reaction with ethyl nitrite in liquid ammonia to form 4-aldoximcs and with ethyl benzoate in the presence of KOC2H to form phenacyl derivatives. 

The monobenzo-fused derivatives of 1,4-dioxin, 1,4-oxathiin and 1,4-dithiin, (345), (346) and (347), can all be prepared by base-catalyzed reaction between the appropriate 1,2-disubstituted benzene and an a-haloketal via an intermediate 2-alkoxy-2,3-dihydro derivative (348). The pyrolysis of the acetoxy derivative (349) at 450°C gives (345 80%) (67ZC152). 2-Hydroxy-2-phenyl-l,4-benzodioxane, from catechol and phenacyl bromide, is dehydrated to (345) by thionyl chloride in pyridine. 

It was found that basic alumina worked well as the basic catalyst for the in situ dipole generation from the AT-acyl pyridinium salt. A three-component mixture of phenacyl bromide (1 mmol), pyridine (1.2 equiv.) and the acetylene (1.2 equiv.) was thoroughly mixed in basic alumina (1 g) and then irradiated for 8 min at 80% power in a domestic microwave. The products were formed in 87-94% yields when running the reaction under solvent-free conditions and in 60-71% yields when using anhydrous toluene as the solvent. 

If the heterocyclic base contains several pyridine-type nitrogens select can also be observed. Indeno[l,2-b]quinoxalines, for example, are quaternized at the N-10 atom.110 The alkylation of heterocycles conta one pyrrole-type nitrogen and several pyridine-type nitrogens is appar selective (e.g., indolo[2,3-b]quinoxaline).201 The yields of quaternary however, are extremely low,201 even if phenacyl halides or a-halo ester used.207 Perhaps the resultant quaternary salts are dealkylated.200,207... 

The mass spectra of benzofused pseudoazulenes 65 and 80 -83 show the mass ion as the base peak, and intense peaks are observed that correspond to the doubly charged molecular ion. The authors197 have attributed this fact to the aromaticity of these systems. This conclusion, however, cannot be drawn for all pseudoazulenes since the relative intensity of the mass ion for 26b is only 5.5%,55 for 4-methyl-4H-cyclopenta[b]quinoline 64%, 14 for 5-methyl-5/f-cyclopenta[c]quinoline7.0%,123andfor2-phenacyl-9-benzoyl-2H-indeno[2,1-fo] pyridine 18%.105... 

Phenacylisothiazolium salts were prepared by fusion of isothiazoles with phenacyl bromide (85BSB149). Treatment of the salt with pyridine afforded the 2-benzoyl-2//-l,3-thiazines (44) via intramolecular nucleophilic attack on the sulfur atom (Scheme 25). 

Methanolysis of die sulfonates (175)141 and the reaction of the sulfonate ester (102) with hydroxylamine (103)88 were looked at earlier. Yoh and co-workers have looked at die reactions of (Z)-phenylediyl (X)-benzenesulfonates with (Y)-pyridines in acetonidile under pressure and die structure-reactivity relationships established show that as die pressure is increased die mechanism moves from a dissociative 5n2 to early-type concerted 5k2.276 In otiier sdtdies also under pressure the same group found that a mechanistic change from associative, k 2 to late-type 5n2 occurs as the pressure is increased in die reaction of (Z)-phenacyl (X)-benzenesvdfonates with (Y)-pyridines in acetone.277... 

The hydrolysis of ethanoic anhydride [47] and the reaction between phenacyl bromide and pyridine to give phenacylpyridinium bromide (Equation 3.29, an example of the Menschutkin reaction) are reported cases of kinetics studies by conductance monitoring [48],... 

Dimethylaminovinyl)-5-oxo-2,7-diphenyl-5//-pyrano 4,3-/ pyridine-3-car-bonitrile (43) with propylamine gave 8-oxo-l-phenacyl-3-phenyl-7-propyl-2,7-naphthyridine-4-carbonitrile (44) (PrNH2, pyridine, reflux 58%).987... 

The most efficient route to the cationic oxazolo[3,2- ]pyridine ring system 69 relies on the cyclocondensation of N-phenacyl-2-pyridones 68 obtained by alkylation of 2-pyridones 67 (Scheme 41) <1967JHC66, CHEC-III(11.10.7.8) 479>. The use of this method is exemplified by the preparation of tricyclic oxazolo[3,2- ]pyridines 71 from the corresponding quinolin-2(l//)-ones 70 (Scheme 42) <2003H131>. 

Ethyl 3-aminofuropyridine-2-carboxylates were reported to be made either from 1-hydroxy-2-cyano-substituted pyridines and ethyl bromoacetate or from l-chloro-2-cyano-substituted pyridines and ethyl glycolate under microwave conditions <07S3247>. Microwave irradiation was also applied in the Rap-Stoermer reaction for the formation of benzo[A] furans from salicylaldehydes and diverse phenacyl bromides and phenacyl iodides... 

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