Thermal and photochemical decomposition of cis- and trans-3,5-diphenyl-1-pyrazoline

The decomposition mechanism of the title compounds 8c and 8t is discussed. Dibenzylic 1,3-biradicals are suggested as intermediates.     

Thermal and photochemical decomposition of 2,6-ditert-butyl-p-benzoquinone diazide

Conclusions It is shown by the EPR method that during the thermal and photochemical decomposition of 2,6-ditert-butyl-p-benzoquinone diazide in solutions the first stage of the reaction is the formation of a carbene, which exists in the triplet state.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2341–2345, October, 1967.The authors express gratitude to N. M. Émanuel for constant interest in the work during its fulfilment.     

Reduction as a probe for benzothiirene intermediates: Thermal and photochemical decomposition of 1,2,3 -benzothiadiazoles.

Four benzothiadiazoles were either heated at reflux or irradiated at room temperature in tetrahydronaphthalene. The base soluble thiols which were obtained were converted to thiolacetates and analyzed by use of infrared and nmr shift-reagent spectroscopy.     

Synthesis, characterization and fluorescence studies of 3,5-diaryl substituted 2-pyrazolines

A series of 2-pyrazolines have been synthesized from α, β unsaturated ketones and hydrazine hydrate with acetic/formic acid in ethanol/DMSO. The structures of 2-pyrazolines have been established by spectroscopic techniques i.e. UV, IR, (1)H NMR, (13)C NMR and micro element analysis. Fluorescence spectra were recorded in the solution at fixed concentration and same excitation wavelength at 290 nm. The absorption band positions of all the compounds broadly lie between 280 and 336 nm and fluorescence band positions in the range between 300 and 370 nm, the near ultraviolet region.     

Synthesis and spectral-luminescence properties of 1-(4′-formylphenyl)-3,5-diaryl-2-pyrazolines

It was demonstrated by means of the IR and PMR spectra that 1-phenyl-3,5-diaryl-2-pyrazolines that contain a grouping with a strong electron-acceptor effect, viz. a 4-nitrophenyl or 4-naphthalanhydride group or a 1,8-naphthoylene-1,2-benzimidazole fragment, in the 3 position undergo Vilsmeier formylation, like unsubstituted 1,3,5-triphenyl-2-pyrazoline, in the para position of the 1-phenyl ring. An investigation of the spectral-luminescence properties of the synthesized 1-(4-formylphenyl)-3,5-diaryl-2-pyrazolines showed that the introduction in the 1-phenyl ring of an electron-acceptor aldehyde group, which is inferior with respect to its acceptor effect to the groupings in the 3 position of the heteroring, does not change the nature of the long-wave absorption band. Substantial hypsochromic and hypsofluoric effects as compared with the corresponding 1-phenyl-unsubstituted compounds are noted in the electronic spectra of these compounds.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 807–811, June, 1982.The authors thank I. D. Kalikhman for recording the PMR spectra.     

Reactions of 4-phenyl-1,2,4-triazoline-3,5-dione with 2-pyrazolines

4-Phenyl-1,2,4-triazoline-3,5-dione (PTAD) acts as an efficient Michael acceptor in reactions with 1-unsubstituted 2-pyrazolines, giving substituted (3,5-dioxo-4-phenyl-1,2,4-triazol-idin-1-yl)-1-pyrazolines in quantitative yields. Through elimination of molecular nitrogen, the latter are easily transformed into the corresponding cyclopropanes. A reaction of methyl 5-methyl-2-pyrazoline-5-carboxylate with a twofold excess of PTAD leads to an intermediate bisadduct, which undergoes dediazotization to form a 1,3,5-triazabicyclo[3.3.0]octane-2,4-dione derivative. 1-Substituted 2-pyrazolines also add to PTAD with the exception that the 2-pyrazoline structure is retained in the product because of the migration of the C(3)H proton to PTAD.     

Synthesis and thermal decomposition of 3-aroyl-4-aryl-2-pyrazolines

Summary 3-Aroyl-4-aryl-2-pyrazolines (21–40) have been synthesized by the reaction of ,-unsaturated ketones (1–20) with diazomethane. These 2-pyrazolines gave -methyl-,-unsaturated ketones (41–46) on thermal denitrogenation.Dedicated to Prof. Dr.F. Sauter on the occasion of his 65^th birthday     

Thermal decomposition of azoisopropane. I. Primary decomposition processes

The thermal decomposition of azoisopropane (AIP) was studied by detailed product analysis in the temperature and pressure intervals 498–563 K and 0.67–5.33 kPa. Besides the predominant termination and hydrogen-abstraction reaction of the 2-propyl radical, the decomposition is characterized by a very short chain process. The following rate constants were determined from the measurements for the following reactions:      

Thermal decomposition of azoisopropane. II. Secondary decomposition processes

The thermal decomposition of azoisopropane (AIP) was studied in the presence of various quantities of propylene in the temperature and pressure intervals 498–553 K and 3.33–5.33 kPa. The inhibition functions relating to formation of the products were determined; these proved a good basis for interpretation of the formation of the secondary decompositon products of AIP. The experimental data support the conception that the βμ radical—radical reaction occurs. The product of this is not stable; its decomposition is one of the sources of the secondary products. The ratio of the rate constants was determined for the following reactions:      

Thermal and photochemical reactivity of phosphaalkenes

Abstract

The reactivity of acyclic dicoordinated phosphorus derivatives has intensively been studied. Nevertheless, up to date, a very few examples of photochemical reactivity of these compounds have been described. We wish to report here some thermal and photochemical reactions of phosphaalkenes 1–4. ¹     

Oscillatory photochemical decomposition of tetrathionate ion

When subject to illumination, tetrathionate ion decomposes in an oscillatory fashion with a period of about 1 h to yield products identified as colloidal sulfur and trithionate ion. This system represents the first experimental example of a stirred, batch photochemical oscillator. A simple model consisting of four reaction steps and four adjustable rate parameters gives good agreement with the observed oscillatory behavior.     

Thermal decomposition of 1-ethyl-5-iodotetrazole

The thermal decomposition of 1-ethyl-5-iodotetrazole in a melt and in solutions was studied using thermogravimetry, manometry, pyrolytic mass spectrometry, and IR spectroscopy. The kinetic and activation parameters of the process and the nature of the decomposition products were determined. The reaction mechanism is assumed to involve equilibrium tautomeric rearrangement of the tetrazole to azidoazomethine form followed by homolytic cleavage of the C-I bond.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1923–1926, November, 1994.The authors are grateful to O. A. Ivashkevich and P. N. Gaponic (Belarussian State University), who provided the samples of the tetrazole.     

Preparation of the simplest Δ1-pyrazolines by isomerization of Δ2-pyrazolines

²-Pyrazolines that do not have substituants in the 1- and 3-positions are not capable of isomerization to 3-substituted pyrazolines and can be converted to ¹-pyrazolines by slow distillation in the presence of bases. This method, which is completely analogous to the synthesis of azo compounds from alkylhydrazones, gives good results when applied to 4-alkyl- and 5,5-dialkyl-²-pyrazolines and makes it possible to obtain the corresponding ¹-pyrazolines in yields of 40–70%. 4-Ethyl-, 5-methyl-5-ethyl-, and 5,5-diethyl-¹-pyrazolines are described for the first time.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 956–957, July, 1971.     

Synthesis and Antimicrobial Activities of Some 1-[(N,N-Disubstitutedthiocarbamoylthio)acetyl]-3,5-diaryl-2-pyrazolines

The increasing clinical importance of drug-resistant fungal and bacterial pathogens has lent additional urgency to microbiological research and new antimicrobial compound development. For this purpose, new pyrazoline derivatives were synthesized and evaluated for antimicrobial activity.

Some 1-[(N, N-disubstitutedthiocarbamoylthio)acetyl]-3,5-diaryl-2-pyrazolines derivatives were synthesized by reacting 1-(chloroacetyl)-3,5-diaryl-2-pyrazolines with appropriate potassium salts of secondary amine dithiocarbamic acids. The chemical structures of the compounds were elucidated by IR, ¹ H-NMR, and FAB⁺-MS spectral data. Their antimicrobial activities against Staphylococcus aureus (B-767), Escherichia coli (B-3704), Pseudomonas aeruginosa (ATCC 27853), Proteus vulgaris (NRLL B-123), and Candida albicans (NRRL-27077) were investigated. The results showed that some of the compounds have notable activity against S. aureus and C. albicans.     

Synthesis of 1H-3-pyrazolines

Two syntheses of the 1H-3-pyrazoline system 17 are described. The syntheses make use of the ability of the azine system to act as 1,3-dipolar species in [3+2] cycloaddition reactions. The spectra data of the new compounds are discussed (IR, ¹H NMR and ¹⁹F NMR).     

Formation of polycyclic hydrocarbons containing a spiropentane or methylenecyclobutane moiety upon thermal decomposition of cyclopropane-containing 1-pyrazolines

1-Pyrazolines1 and2 obtained by 1,3-dipolar cycloaddition of diazocyclopropane to norbornene or deltacyclene undergo dediazotization at 410–450°C to give a mixture of strained hydrocarbons, namely, spirocyclopropane-1,3'-tricyclo[3.2.1.0^2,4]octane (4) or spiro{cyclopropane-1,4'-pentacyclo[4.4.0.0^2,8.0^3,5.0^7,9]decane} (6) and isomeric tricyclo[5.2.1.0^2,5]dec-5-enes (5) or pentacyclo[6.4.0.0^2,10.0^3,6.0^9,11]dec-6-enes (7) in a 30–70% overall yield. An increase in temperature favors the isomerization of spiro hydrocarbons4 and6 to the respective unsaturated hydrocarbons5 and7. The latter undergo cyclopropanation with diazomethane in the presence of Pd(acac)₂ or (PhO)₃P · CuCl to afford polycyclanes9a,b or10a,b containing a spiro[2.3]hexane moiety condensed at thecis-1,4 position. Unsaturated 1-pyrazoline3 obtained from diazocyclopropane and norbornadiene decomposes at 330–370°C with elimination of cyclopentadiene to give 3(5)-vinylpyrazole in a yield up to 75%.Some of the results reported in this paper have been presented at the VIIIth European Symposium on organic chemistry (Barcelona, August–September 1993),cf. Ref. 1.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 662–667, April, 1994.This study was financially supported by the Russian Fund for Fundamental Research (grant 94-03-08902).     

PMR spectfa of alkyl-substituted δ1-pyrazolines

Data from the PMR spectra of ¹-pyrazollnes and their acyclic analogs — azo compounds — were compared. It is shown that the difference in the chemical shifts of similar fragments in these compounds is due to the peculiarities of the three-dimensional structures, which lead to different contributions to shielding from the unshared electron pairs of nitrogen and the magnetically anisotropic N=N bond.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 987–989, July, 1974.     

Thermal decomposition of 1-butyne in shock waves

1-Butyne diluted with Ar was heated behind reflected shock waves over the temperature range of 1100–1600 K and the total density range of 1.36 × 10^?5?1.75 × 10^?5 mol/cm³. Reaction products were analyzed by gas-chromatography. The progress of the reaction was followed by IR laser kinetic absorption spectroscopy. The products were CH₄, C₂H₂, C₂H₄, C₂H₆, allene, propyne, C₄H₂, vinylacetyiene, 1,2- butadiene, 1,3-butadiene, and benzene. The present data were successfully modeled with a 80 reaction mechanism. 1-Butyne was found to isomerize to 1,2-butadiene. The initial decomposition was dominated by 1-butyne → C₃H₃ + CH₃ under these conditions. Rate constant expressions were derived for the decomposition to be k₇ = 3.0 × 10¹⁵ exp(?75800 cal/RT) s^?1 and for the isomerization to be k₄ = 2.5 × 10¹³ exp(?65000 cal/RT) s^?1. The activation energy 75.8 kcal/mol was cited from literature value and the activation energy 65 kcal/mol was assumed. These rate constant expressions are applicable under the present experimental conditions, 1100–1600 K and 1.23–2.30 atm. © 1995 John Wiley & Sons, Inc.