Metalation of bromodiazines. Diazines XL

The syntheses of 2‐bromopyrazine, 2,4‐dibromopyrimidines, and 3‐bromo‐6‐phenylpyrazine were improved and their metalation with lithium alkylamides was studied.     

Metalation of sulfoxides in the benzodiazine series. Diazines. Part 44

The metalation of 12 benzodiazines sulfoxides was tested. This reaction was effective with 3-sulfinylcinnolines, 5-phenylsulfinyl-2-tert-butylquinazoline and 8-tert-butylsulfinyl-2-tert-butyl-4(3H)-quinazolinone.     

Syntheses of N‐diazinyl thiocarboxamides and of thiazolodiazines. Metalation studies. Diazines XXXIII

Two thiazolodiazines were prepared from the corresponding N‐diazinylcarboxamides by use of Lawesson's reagent. Two N‐diazinylthiocarboxamides were obtained from amino derivatives by reaction with methyl phenyldithiocarboxylate. The metalation of these four compounds was studied and the thiazolodiazines could be functionalized.     

Metalation reactions. : IV. Metalation of o-alkyl- and o,o′-dialkyl-substituted alkylthiobenzenes

Metalation of o-alkyl- and o,o′-dialkylsubstituted alkylthiobenzenes with n-butyllithium, in the presence and absence of TMEDA, has been investigated. The results showed that metalation at the thioalkyl carbon probably occurs by direct attack of the organolithium reagent, although a transmetalation reaction cannot be excluded in some cases. It has also been found that benzylic, thio-methylic, and ring metalation occurs in ether alone, whereas mainly thio-methylic or ring metalation occurs in the presence of TMEDA.     

Vibrational and electronic absorption spectra of 4-chloro 2-methyl, 4-chloro 3-methyl and 6-chloro 3-methyl phenols

The infrared spectra of 4-Cl 2-Me, 4-Cl 3-Me and 6-Cl 3-Me phenols have been recorded. The vibrational spectrum has been analysed assuming that the molecules belong toC _s point group and a tentative assignment of the observed frequencies to various modes of vibration has been proposed. The near ultraviolet absorption spectrum of these compounds has also been recorded. Assuming the transition to be electronically allowed the strongest band on the longer wavelength side has been assigned as the (0, 0) band in each case. The spectrum has been analysed in terms of several excited state frequencies which have been correlated with the ground state frequencies observed in the infrared spectrum.     

Metalation of t-butyl sulfoxides,sulfones and sulfonamides of pyridazine and pyrazine. Metalation of diazines. XX

In the pyridazine series, the use of tert-butylsulfinyl and tert-butylsulfonyl as ortho directing groups for metalation has been tested. Various functionalized products were obtained in good yields. In the case of 3-tert-butylsulfinyl-6-methoxypyridazine, the metalation was regioselective in ortho to the sulfinyl group. The metalation of 2-tert-butylsulfinyl and 2-tert-butylsulfonylpyrazine gave low to moderate yields. Synthesis of diazinesulfonamides were improved and the metalation of N-tert-butylsulfonamidopyrazine was achieved.     

Photoacoustic spectra of naphthalenes: 2-fluoro, 2-chloro, 2-bromo and 2-hydroxynaphthalenes

The photoacoustic spectra of 2-fluoro, 2-chloro, 2-bromo and 2-hydroxynaphthalenes have been recorded in the powder form. A method of analysing these spectra is suggested in the light of solution phase and vapour phase data on these molecules. It is observed that the non-radiative transitions in the region of 200 nm decrease in these molecules as the substituent in the 2-position is changed from F to Cl to Br to OH.     

Metalation of diazines. VI. Metalation of pivaloylaminopyrazine and N-t-butylpyrazinamide. Unusual regioselectivity in the metalation reaction

Metalation of pivalamidopyrazine and N-t-butylpyrazinamide were studied. For pivalamido pyrazine the yields were poor and some addition products were isolated. The metalation of t-butylpyrazinamide was successful and a curious regioselectivity was highlighted.     

Copolymerization of acrylonitrile with 3-chloro, 2-hydroxy-propyl acrylate and methacrylate

Acrylonitrile (AN) was copolymerized with 3-chloro, 2-hydroxy propyl acrylate (CHPA) and 3-chloro, 2-hydroxy-propyl methacrylate (CHPMA) in water and water-acetone medium at 40°C with potassium persulfate and sodium metabisulfite as redox initiators. Copolymer composition was determined from the nitrogen content. The reactivity ratios for the AN-CHPMA system were also calculated by the Kelen–Tudos method. The reactivity ratio r₂ (CHPMA) was higher for the AN-CHPMA system in both media, which indicated higher reactivity of CHPMA toward the propagation species. Addition of acetone decreases r₂ and increases r₁. It was found that the copolymers prepared in water medium were not completely soluble in dimethylformamide (DMF); the insoluble fraction was rich in CHPA/CHPMA and increased with increasing comonomer composition. The influence of the acrylate comonomer on properties such as solubility and intrinsic viscosity was also studied.     

The vibrational spectra, assignments and ab initio/DFT analysis for 3-chloro, 4-chloro and 5-chloro-2-methylphenyl isocyanates

The Raman (3500-50 cm(-1)) and infrared (4000-200 cm(-1)) spectra of 3-chloro, 4-chloro and 5-chloro-2-methylphenyl isocyanates have been measured. Ab initio and density functional theory calculations, at the levels of RHF/6-311G* and B3LYP/6-311G*, have been performed: energies, optimized geometrical parameters, vibrational frequencies, infrared intensities, Raman activities, depolarization ratios and nuclear displacements are obtained. Potential energy distributions (PEDs) and normal modes, for the spectral data computed at B3LYP/6-311G*, have also been obtained from a force-field calculations. A complete vibrational assignments of the observed spectra have been proposed. The force-field calculations have shown that, several of the normal modes are coupled, as is the case with large molecular systems possessing very low or no symmetry, such as investigated in the present study. Further, the investigation of the internal rotation of the isocyanate, NCO, by B3LYP/6-31G* level of theory has shown that the moiety maintains nearly the same orientation in all the three compounds (approximately 140-145 degrees tilt to the para-position) as in phenyl isocyanate. Two conformers, cis and trans forms, with respect to the substituents, NCO and CH(3), have been determined: the cis form lies above trans form by less than a kilocalorie per mole for each compound.     

Conformational preferences of 2-methoxy, 2-methylthio, and 2-methylselenocyclohexyl-N,N-dimethylcarbamate: a theoretical and experimental investigation

Studies on the conformational equilibria of 2-methoxy, 2-methylthio, and 2-methylselenocyclohexyl-N,N-dimethylcarbamate are reported. DNMR spectroscopy experiments at 203 K provided the percentages of each conformer in equilibrium. Theoretical calculations using the MP2, B3LYP, and B971 methods with cc-pVDZ basis set were applied to determine the differences in energy between the conformers. The analysis of the potential energy surface (PES) for each conformer showed the presence of two rotamers. NBO analysis provided an explanation of the factors (hyperconjugative and steric interactions) that drive rotamer and conformer preferences.     

Vibrational spectra and assignments for 2-chloro and 2-bromo derivatives of thiophene,selenophene and tellurophene

The infrared spectra of 2-chloro-, 2-bromo-thiophene, -selenophene and -tellurophene as liquids have been investigated from 4000 to 300 cm⁻¹. The laser Raman spectra of these liquids have also been recorded and depolarization values have been measured. An assignment of the 21 fundamental vibrations is proposed, based on group frequency correlations, Raman polarization data and comparison with the spectra of parent molecules.     

Quinoline nitroxide radicals. Ipso-attack in the reaction between 2-methoxy and 2-cyanoquinoline N-oxide,and phenylmagnesium bromide

2-Methoxy and 2-cyanoquinoline N-oxide, when treated with phenylmagnesium bromide, undergo a nucleophilic ipso-attack at C-2, yielding, by elimination of methoxymagnesium bromide or cyanomagnesium bromide, the corresponding 2-phenylquinoline N-oxides, which react with the excess of Grignard reagents forming 2,2-diphenylquinoline 1-oxyls. Even when the methoxy and cyano groups are in position 4, the attack by the Grignard reagent takes place at C-2 giving 2-phenylquinolines and 2-phenylquinoline N-oxides by elimination of hydroxymagnesium bromide and bromomagnesium hydride, respectively; the formation of 2,2-diphenylquinoline l-oxyls in these reactions is discussed.     

Synthesis of pyrazine alcaloids from Botryllus leachi. Diazines 43

[reaction: see text] Regioselective metalation of pyrazines and cross-coupling reactions provides an easy access to botryllazines A and B and to an isomer of botryllazine A with good yields from chloropyrazine.     

Synthesis of new polyaza heterocycles. Part 42: Diazines

Using Pd-catalyzed Stille cross-coupling reactions, we report here the synthesis of various mono- or bis(tri-n-butylstannyl)diazines which were reacted with various halogenated diazines to access to various polyaza heterocyclic derivatives.     

Photodegradation of 2-chloro substituted phenothiazines in alcohols

The mechanisms that trigger the phototoxic response to 2-chlorophenothiazine derivatives are still unknown. To better understand the relationship between the molecular structure of halogenated phenothiazines and their phototoxic activity, their photophysics and photochemistry were studied in several alcohols. The photodestruction quantum yields were determined under anaerobic conditions using monochromatic light (313 nm). Absorption- and emission-spectroscopy, ¹H- and ¹³C-NMR and GC-MS were used to characterize the photoproducts and reference compounds. An electron transfer mechanism had been previously proposed by Bunce et al . ( J. Med. Chem . 22 , 202–204) to explain the large difference between the photodestruction quantum yield of 2-chlorpromazine (φ = 0.46) and 2-chlorphenothiazine (φ = 0.20). According to these authors, the alkylamino chain transfers an electron to the phenothiazine moiety. Our results demonstrate that this mechanism is incorrect, because the photodestruction quantum yields of all chlorinated derivatives of this study are the same under the same conditions of solvent and irradiation wavelength. The quantum yield has no dependence on the 10-substituent, but it depends on the solvent. The percentage of each photoproduct, on the other hand, strongly depends on that substituent, but not very much on the solvent. Finally, it is demonstrated that the phototoxic effect of chlorinated phenothiazines is not related to the photodechlorination, although both processes share the same transient.