Kamini Kaul

Efficient synthesis of 3-aroylcinnolines from aryl methyl ketones

Abstract An efficient synthesis of 3-aroylcinnolines starting from the appropriate aryl methyl ketones is described. The latter were converted in two steps to the corresponding 3-oxo-3-aryl-2-arylhydrazonopropanals, which upon acid catalyzed cyclization in conc. sulfuric acid or polyphosphoric acid (PPA) led to the corresponding 3-aroylcinnolines.

Kinetics and mechanism of thermal gas-phase elimination of ?-substituted carboxylic acids: role of relative basicity of ?-substituents and acidity of incipient proton

2-Phenoxypropanoic acid together with five of its aryl derivatives, its phenylthio and its N-phenylamino analogues were pyrolyzed at 494–566 K. The reactions were homogeneous, polar and free from catalytic and radical pathways, and obeyed a first-order rate equation. The limits of the Arrhenius log A (s−1) and E (kJ mol−1) values obtained for these reactions averaged 11.98 ± 1.71 and 158.1 ± 17.4, respectively. Analysis of the pyrolysates showed the elimination products to be carbon monoxide, acetaldehyde and the corresponding phenol, thiophenol or aniline compounds. The pyrolysis of 2-phenoxy- and 2-(N-phenylamino)-1-propanol was also investigated over the temperature range 638–792 K. The kinetic results and products analysis lend support to a reaction pathway involving a five-membered cyclic polar transition state. Copyright

Kinetics and mechanism of pyrolysis of sulphonyl hydrazones and oximes. Part 2—Structural effects and molecular reactivity

The kinetics and products of the pyrolytic reaction of six tosyl arenecarboxaldoximes were studied over the temperature range ca 334 – 401 K to yield the following Arrhenius log A/s−1 and Ea / kJ mol−1, respectively: 10.92 and 98.25 for tosyl benzaldoxime and 10.83 and 100.4 for m-nitro-, 10.66 and 97.53 for p-chloro-, 11.80 and 107.8 for m-chloro-, 11.60 and 101.5 for p-methyl- and 10.84 and 97.75 for p-methoxybenzaldehyde O-[(4-methylphenyl)sulphonyl]oxime. At 500 K, the oxime compounds were found to be 9.4 × 103 – 2.7 × 104-fold more reactive than their hydrazone analogues. Copyright

Gas-phase pyrolytic reactions of N-ethyl, N-isopropyl, and N-t-butyl substituted 2-aminopyrazine and 2-aminopyrimidine

The rates of gas-phase elimination of N-ethyl (1), N-isopropyl (2), N-t-butyl (3) substituted 2-aminopyrazine and N-ethyl (4), N-isopropyl (5), and N-t-butyl (6) substituted 2-aminopyrimidine have been measured. The compounds undergo unimolecular first-order pyrolytic reactions. The relative rates of the primary:secondary;tertiary alkyl homologues at 600 K are 1:14.4:38.0 for the pyrazines and 1:20.8:162.5 for the pyrimidines, respectively. The reactivities of these compounds have been compared with those of the alkoxy analogues and with each other. Product analyses, together with the kinetic data, were used to outline a feasible pathway for the elimination reaction of the compounds under study.

Kinetics and mechanism of pyrolysis of sulphonyl hydrazones and oximes. Part 1. Contribution to reactivity from hydrazone HNN and oxime ON bond polarity

Abstract Rates were obtained for the pyrolysis of tosyl arenecarboxaldehyde hydrazones (1–5), and mesyl benzaldoxime (6). The substituted tosyl sulphonamides (TsHNN=CHAr: 1–5) and the mesylate (6) gave in a novel pyrolytic reaction the following Arrhenius log A/s−1 and Ea/kJ mol−1 values, respectively: 12.70 and 157.7 (1, ArC6H5), 12.29 and 152.6 (2, p -NO2C6H4), 11.85 and 148.2 (3, m -NO2C6H4), 12.17 and 152.0 (4, p -ClC6H4), 11.01 and 140.8 (5, p -CH3OC6H4), and 12.96 and 109.9 for (6). Tosyl benzaldoxime (7) was also studied. The reactions yielded cyanoarenes together with sulphonic acids from 6 and 7, and p -methylbenzenesulphonamide from compounds 1–5.

1-Substituted 3-Dimethylaminoprop-2-en-1-ones as Building Blocks in Heterocyclic Synthesis: Routes to 6-Aryl- and 6-Heteroaryl-2H-pyran-2-ones and 6- and 4-Arylpyridin-2(1H)-ones

Several new 6-substituted-3-acylamino-2H-pyran-2-ones 6a–j have been prepared from the reaction of enaminones 4a–f with N-acyl- and N-benzoyl-glycines; the enaminones 4a–c react with malononitrile in ethanol solution and in the presence of a base to yield amides 11a–c which are converted into 6-aryl-1,2-dihydro-2-oxypyridine-3-carbonitriles 13a–c on reflux in acetic acid.

Studies with Condensed Azines: New Routes toPyrazolo[3,4-b]pyridines andPyrrolo[3,2-b]pyridines

Several condensed pyrazole derivatives are obtainedfrom the reaction of 3-methyl-1-phenylpyrazol-5-amine (1) withα,β-unsaturated ketones, α,β-unsaturatednitriles and isothiocyanates.

Neighbouring group participation in the gas‐phase pyrolysis kinetics of 4‐(N‐methyl‐N‐phenylamino)‐1‐butyl acetate and 4‐(N‐phenylamino)‐1‐butyl acetate

The pyrolysis kinetics of two phenylaminobutyl acetates were determined in a static system over the temperature range 359.7–399.6 °C and the pressure range 23.8–95 Torr. The reactions, in vessels seasoned with allyl bromide and in the presence of the free radical inhibitor toluene, are homogeneous and unimolecular, and obey a first-order rate law. The overall rate coefficients are expressed by the following equations: for 4-(N-methyl-N-phenylamino)-1-butyl acetate, log[k1 (s−1)] = (13.92 ± 0.36) − (210.4 ± 4.5) kJ mol−1 (2.303RT)−1; and for 4-(N-phenylamino)-1-butyl acetate, log[k1 (s−1)] = (12.03 ± 0.43) − (188.3 ± 5.3) kJ mol−1 (2.303RT)−1. The decomposition of these substrates undergoes a parallel reaction. The predominant primary product, the corresponding heterocyclic product, appears to be the result of an anchimeric assistance of the amino substituent for a back-side displacement. This suggests that an incipient ion-pair type of mechanism may be operating during the process of elimination. The Arrhenius expressions for the parallel decomposition of each of the aminobutyl acetate substrates are presented and discussed. Copyright

Gas-phase pyrolytic reactions of esters of 2-pyridine and 8-quinoline sulfonic acid

The rates of gas-phase thermal elimination reaction of esters of 2-pyridine sulfonic acid and 8-quinoline sulfonic acid have been measured over at least 50° for each compound. The relative rates of the first-order unimolecular decomposition at 500 K for the primary:secondary esters suggest that CO bond breaking is kinetically more significant than CH bond breaking, leading to a transition state of carbocationic character. This is consistent with the electron-donating effect provided by the methoxy substituent in 2-p-methoxyphenylethyl of 2-pyridine and 8-quinoline sulfonate esters stabilizing the carbocation center.

Substituent effects in the gas-phase pyrolysis of 4-(N-arylamino)-1-butyl acetate and 5-(N-arylamino)- 1-pentyl acetate

A kinetic study of the gas-phase pyrolysis of 4- and 5-(N-arylamino)-1-butyl and -1-pentyl acetate was made. Each ester was pyrolysed at five or six different temperatures and over a temperature range not less than 50 °C. These reactions were homogeneous and unimolecular. The reactivities of these compounds were compared with those of the parent compounds 4- and 5-(N-phenyl)-1-butyl and -1-pentyl acetate and with each other. The products of the decomposition reaction of these compounds suggest an anchimeric assistance of the amino substituent for a trans elimination, indicating that an ion-pair type of mechanism may be operating during the process of elimination. Copyright