Bromination of sydnones. II Bromination of 3-(2-aminophenyl)sydnone and related compounds

Bromination of 3-(2-aminophenyl)sydnone 2 under a variety of conditions is reported. The products obtained are interrelated by a series of subsequent reactions. One major product is the bromoaryl compound 8, the first example of bromination on the aryl rather than sydnone ring when the two are in competition. Surprisingly, bromoaminosydnone 9, prepared from its nitro analogue, was not among the products obtained by direct bromination of 2.     

Reactions of activated aryl sydnones with electrophiles

Electrophilic substitution on the aryl or sydnone ring of some ortho-substituted activated N-aryl-sydnones is reported.     

Chlorination and Bromination of Dialkyl Tellurides

The reactions of dialkyl tellurides R₂Te (R = C₂H₅, n‐C₃H₇, i‐C₃H₇, c‐C₆H₁₁) with sulfuryl chloride and bromine were examined. The dialkyltellurium(IV) dichlorides (C₂H₅)₂TeCl₂ ( 1 ), (n‐C₃H₇)₂TeCl₂ ( 2 ), (i‐C₃H₇)₂TeCl₂ ( 3 ) and (c‐C₆H₁₁)₂TeCl₂ ( 4 ) were obtained upon reaction with stoichiometric amounts of SO₂Cl₂. Excess of SO₂Cl₂ resulted in formation of mixtures of R₂TeCl₂ and RTeCl₃. Treatment of (C₂H₅)₂Te and (n‐C₃H₇)₂Te with excess bromine gave the dialkyltellurium(IV) dibromides (C₂H₅)₂TeBr₂ ( 5 ) and (n‐C₃H₇)₂TeBr₂ ( 6 ), whereas (i‐C₃H₇)₂Te and (c‐C₆H₁₁)₂Te yielded the alkyltellurium(IV) tribromides i‐C₃H₇TeBr₃ ( 7 ) and c‐C₆H₁₁TeBr₃ ( 8 ). Equimolar amounts of bromine resulted in mixtures of R₂Te and RTeBr₃. All products were identified and characterized by analytical and spectroscopic methods. n‐Propyl tellurium tribromide ( 9 ) was detected from a solution of the dibromide 6 after prolonged periods. The crystal structures of 7 , 8 and 9 were determined.     

Bromination of photochromic spironaphthoxazines

Direct bromination of photochromic compounds of the spironaphthoxazine and spironaphthopyran series was performed using N-bromosuccinimide to obtain both photochromic bromine-substituted spiro compounds and nonphotochromic 2-(naphtho[1,2-d]oxazol-2-yl)-3H-indolium bromides. The structures of the resulting products were established by NMR spectroscopy and mass spectrometry. The mechanism of bromination taking into account the involvement of both closed and open (colored) forms of spiro compounds was proposed.     

3-(Carboxypolyme thylene) sydnones

Spectral data and pK _a values found for a number of 3-(carboxypolymethylene)sydnones made it possible to establish the mutual effect of a heterocyclic ring and a carboxyl group in these compounds and to confirm the high electron-acceptor character of a 3-sydnonyl substituent.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 479–485, April, 1973.     

Bromination of single crystals of trans-1,4-polybutadiene. Thermal behavior

It is demonstrated by several methods (DSC, infrared spectroscopy, and small-angle and wideangle x-ray diffraction) that bromination of suspensions of single crystals of trans-1,4-polybutadiene is selective at the fold surface. As the thickness of the single crystals is increased, a larger number of double bonds per fold are brominated, i.e. a larger number of repeat units become accessible to bromine. This is consistent with an increase in the thickness of disordered surface layers with the crystallization temperature. A reduction of 40–60% in overall apparent enthalpies of transition and of melting and reduced ability of brominated single crystals to refold following annealing are also observed. Crystallization from the melt of trans-1,4-PBD with [ CH₂? CHB_r? CHB_r? CH₂ ] units along the chain is interpreted by assuming that some of these units are incorporated in the crystal lattice as defects.     

Bromination of dichloromethane,chlorofluoromethane, and dichlorofluoromethane.

Dichloromethane, chlorofluoromethane, and dichlorofluoromethane have been brominated competitively with each other and with chloroform and methyl chloride. Using the literature values for the rates of bromination of these latter two compounds, the rate constants for the three former compounds have been determined: where R is taken to be 1.987 cal deg^?1 mol^?1 (1 cal = 4.186 J).     

Couloamperometry. A fast kinetic technique for halogenations. I. Bromination rate constants of highly reactive enol ethers

A new couloamperometric apparatus has been designed to extend the range of this kinetic technique to the measurement of very high rate constants, 10⁸M^?1s^?1, by using TFCR-EXSEL conditions (TFCR—very low reactant concentration; EXSEL—salt excess), which give half-lives of a few seconds for very fast second-order reactions. Very low faradaic currents, in the nanoampere range for halogens, corresponding to very low reactant concentrations of 10^?8–10^?9M, are measured selectively by compensating the eddy currents, principally the residual and the induced currents. When the electroactive species is bromine, the concentration is demonstrated to be linearly related to the limiting reduction current in the very low concentration range. The upper limit of this technique for bromination is at present 3 × 10⁸M^?1s^?1. The method is applied to the kinetic study of highly reactive enol ethers EtO-C(R) = CH-R′, where R and R′ are H or Me. A value of 2.2 × 10⁸M^?1s^?1 is obtained for k, the rate constant for free bromine addition to EtO-CH = CH₂, by extrapolating the kinetic bromide ion effects to [Br^?] = 0. An α-methyl effect (k_α-Me/k_H)_EtO of 15 is found; this is a small decrease in the methyl effect compared to the marked increase in the double bond reactivity. For the enol acetate MeCOO-CH = CH₂, whose rate constant is 6 × 10²M^?1s^?1, (k_α-Me/k_H)_OCOMe is 21. The dependence of substituent effects on reactivity is discussed in terms of the Hammond effect on the transition state position and of charge delocalization by group G of olefins G-CH = CH₂.     

Meso-ionic compounds. XI,photochromic 4-halogeno-3-(3-pyridyl)sydnones

Halogenation of 3-(3-pyridyl)sydnone with N-halosuccinimides in chloroform afforded the 4-halogeno-3-(3-pyridyl)sydnones where X = CI, Br, I. The 4-chloro- and 4-bromopyridylsydnones were photochromic. 3-(3-Pyridyl)sydnone was obtained in both high yield and purity by dehydration of N-nitroso-N-(3-pyridyl)glycine with trifluoroacetic anhydride.     

Synthesis of new 3-(phenoxyphenyl)sydnones marija Šindler-kulyk

The title compounds were prepared by dehydrocyclization of corresponding substituted N-nitrosoglycines obtained from isomeric o-, m- and p-aminodiphenyl ether with ethyl bromoacetate and subsequent nitrosation of the intermediate N-arylsubstituted glycines.     

Selective Bromination of Dehydroacetic Acid with N-Bromosuccinimide

Bromination of dehydroacetic acid has been carried out with N-bromosuccinimide under various conditions. The reactions led to selective bromination, thereby offering efficient synthesis of 3β-bromodehydroacetic acid (3), 3β,5-dibromodehydroacetic acid (4), 3β,3β-dibromodehydroacetic acid (5), and 3β,3β,5-tribromodehydroacetic acid (6).     

Nitrogen NMR sudies of some 15N labelled sydnones and related stuctures

¹⁵N NMR studies on some signly labelled sydnones, N-acetylsydonimines and their hydrochlorides, as well as those on some sydnonimine hydrochlorides, show that in each case protonation takes place at the exocyclic moiety, \documentclass{article}\pagestyle{empty}\begin{document}$ - {\rm O}^ \ominus - \mathop {\rm N}\limits^ \ominus {\rm COCH}_3 \,{\rm or}\, - \mathop {{\rm NH}}\limits^ \ominus $\end{document}, respectively. Complete assignments of the nitrogen chemical shifts are possible for the labelled compounds, including the isomeric structures of N-alkyl–N-cyanomethyl–N–nitrosoamines to which, unstable, free sydnonimines are converted.     

Stereoselective Bromination of 2-Vinyl Chromones Using NBS

A simple one-step synthetic methodology for stereoselective synthesis of E- and Z-3-bromo-2-vinyl chromones in quantitative yield in polar solvents under ambient conditions without the use of catalysts is reported.     

Bromination of N,N'-Substituted Malonodiamides

Aiming at preparation of biologically active compounds a bromination of N,N'-substituted malonodiamides in a glacial acetic acid was carried out. The use of one equiv of bromine provided monobromo derivatives, with two equiv of bromine dibromo-substituted products were obtained. Among the N,N'-dibenzylamides of alkylmalonic acids only the methyl homolog underwent bromination. The structure of compounds was proved by IR and ¹H NMR spectroscopy. The effect of the compounds synthesized on the central nervous system was investigated.     

Mass spectrometry of onium compounds. XXX—Ionisation potentials in structure analysis of sydnones

Comparative studies of the ionisation potentials of some sydnones indicate that these molecules are largely present in the gaseous phase as their valence isomeric N-nitroso ketenes.     

Bromination of methyl substituted 1,2,5-thiadiazoles with N-bromosuccinimide

Bromomethyl-1,2,5-thiadiazoles 2a-c were prepared by bromination of methyl-1,2,5-thiadiazoles 1a-c by NBS in refluxing carbon tetrachloride. When bromination of 1a and 1b was carried out under irradiation of tungusten lamp, mixtures of cis -5a and b and trans-1,2-dibromo-1,2-bis(1,2,5-thiadiazol-3-yl)ethylene ( 6a and b ) were obtained.     

Bromination of CH-acid polynitro compounds by α-Bromopolynitroalkanes

Conclusions It was shown that the nonionized CH-acid polynitro compounds HC(NO₂)₂R and their anions are capable of being brominated by-bromopolynitroalkanes to give BrC(NO₂)₂R.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1093–1098, May, 1980.     

Mesoionic compounds VIII. Synthesis of 3-phenylsydnonyl substituted alkenes. Some new photochromic sydnones

The reactions of 3-phenylsydnonyllithium with a variety of ketones to afford tertiary carbinols 4a-4i and their subsequent dehydration to 4-(3-phenylsydnonyl) alkenes 5a-5i are discussed. Among the alkenes, 2-[4-(3-phenylsydnonyl)]propene ( 5b ) and 1-[4-(3-phenylsydnonyl)]-1-cyclohexene ( 5i ) were photochromic. A Wittig reaction between ethyl-4-(3-phenylsydnonyl)-ketone and methylenetriphenylphosphorane afforded the photochromic 2-[4-(3-phenylsydnon-yl)]-1-butene(5j).     

Bromination of porphyrins (Review)

Methods for the bromination of porphyrins and their derivatives at the meso and β-positions are examined. The dependence of the course of the reactions on the conditions and on the structure of the initial compounds is discussed. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 323-353, March, 2009.     

Bromination of sydnones. I. Reaction with 3-arylsydnones containing electron-donors on the aryl ring

Bromination has been examined for a series of 3-arylsydnones (1) with electron donors (dimethyl to dimethoxy) on the aryl ring. In no example was exclusive aryl ring bromination observed, however, exclusive sydnone ring bromination could be realized in every case. For two dimethoxyphenyl examples both aryl and sydnone ring bromination occurred.