Mass spectrometry of 2,5-dimercapto-1,3,4-thiadiazole methyl and aryl derivatives

The most significant mass spectral features of thirteen title compounds are discussed. Fissions occur across the thiadiazole ring, leading to the formation of [M-RSCN]^+˙ and \documentclass{article}\pagestyle{empty}\begin{document}${\rm R - }\mathop {\rm S}\limits^{\rm + } = {\rm C} = {\rm S}$\end{document} ions. In cases where the thiol-thione equilibrium is present in the vapour state, expulsion of CS₂ from the molecular ion is observed. The fragmentation pattern of the compounds having an ortho nitro group in the S-aryl moiety is strongly affected by a prominent ‘ortho effect’.     

Mass spectrometry of substituted 1,3-dihydro-2H-imidazole-2-thiones

The electron impact mass spectra of the 4-formyl-1, 3-dihydro-2H-imidazole-2-thione, its six 1-methyl(n-propyl, n-hexyl)-3-methyl(phenyl)-disubstptuted derivatives, and the 1,3-dihydro-1-phenyl-2H-imidazole-2-thiome are discussed. The fragmentation pattern is strongly influenced by the alkyl or phenyl N-substituents, as well as by the length of the alkyl chain. The odd-electron ions containing an N-phenyl substituent, but not a propyl or hexyl group, eject a hydrogen atom from the phenyl ring, while the presence of a long alkyl chain greatly enhances the loss of the sulphyhydryl radical and facilitates the expulsion of several alkenes, and alkyl and alkenyl radicals.     

Electron impact and methane chemical ionization mass spectrometry of trisilanes and trisiloxanes

The electron impact and methane chemical ionization mass Spectrometry of fifteen trisilanes and trisiloxanes containing various substituents was studied with the aid of exact mass measurements and metastable ion analyses. Migration reactions of the two kinds of compounds are discussed.     

Mass spectra of aryl substituted N-t- butylbenzamides: Substituent effects on unimolecular ion decomposition

The major reactions of aryl substituted N-t-butylbenzamides upon electron-impact involve direct cleavage of a methyl radical, the loss of a butene molecule with the transfer of one hydrogen, or the loss of a butenyl radical with the transfer of two hydrogens. The last of these processes parallels the mass spectral behavior of aliphatic amides. Substituent effects indicate that electron-withdrawing groups on the aromatic ring enhance the two hydrogen transfer process, while electron-donating groups enhance the single hydrogen transfer process. Ion abundances, ionization potentials and appearance potentials are discussed with respect to correlation with σ⁺ values.     

芳环取代的俘精酸酐的合成及光致变色反应研究

本文报道四个芳环取代的俘精酸酐:2-亚异丙基-3-[1-(4-甲氧苯基)-亚乙基]-丁二酸酐(BF1); 2-亚异丁基-3-[1-(4-甲氧苯基)-亚乙基]-丁二酸酐(BF2);2-亚异丙基-3-[1-(α-萘基)-亚乙基]-丁二酸酐(NF1); 2-亚异丙基-3-[1-(β-萘基)-亚乙基]-丁二酸酐(NF2)的合成及其光致变色性质。测定了它们在不同溶剂中光致变色前后的吸收光谱。利用纳秒级激光闪光光解技术研究了它们的光致变色过程, 并讨论了其光致变色机理。结果表明, 这类芳环取代的俘精酸酐的光致环合反应是经过激发单重态进行的快速过程。     

Acid-mediated aryl migration reaction of C-3 aryl substituted pyrrolidinoindolines

Aryl migration reactions of C-3 aryl substituted pyrrolidinoindoline compounds to provide highly conjugated C-2 aryl indole compounds have been discovered. The developed reactions have a wide substrate scope and proceed in high yield under simple acidic conditions. A unique cationic cyclopropane intermediate as the transition state is proposed.     

Synthesis of substituted aryl enol ethers

A facile route toward substituted aryl diarylvinyl ethers 4 is developed from CuI-mediated cross-coupling reaction of substituted phenols 2 with diarylvinyl bromides 3 in the presence of various bidentate-based ligands in DMF. Skeleton 3 is prepared by Yan’s bromomethylenation of diarylketones 1 with CHBr₃–TiCl₄–Mg in the co-solvent of DME and CH₂Cl₂. The synthetic route obtains moderate yields from the one-step operation and the key structure of 4k is confirmed by X-ray crystallographic analysis. The CADD docking experiments of 4k have been included.     

New aryl ethynylene substituted silicon-centered molecules

The reactions of substituted dichlorosilane monomers,Cl₂SiRR′, with two equivalents of lithium aryl acetylide(1), LiC ≡ C-4-C₆H₄-Ph, afford RR′Si(C ≡ C-4-C₆H₄-Ph)₂ (6: R,R′ =CH₃; 7: R = CH₃, R′ = CH=CH₂; 8: R,R′ = Ph). An isomeric mixture of meso, (R,R)- and (S,S)-Bis[2-(N,N-dimethylaminomethyl)ferrocenyl]dichlorosilane (5) was used as starting chlorosilyl compound for reaction with LiC ≡ C-4-C₆H₄-Ph to give (FcN)₂Si(C ≡ C-4-C₆H₄-Ph)₂ (9). A detailedcharacterization of 6, 7, 8 and 9 has been carried out by ¹H-NMR, ¹³C-NMR, ²⁹Si-NMR, IR and UV-VIS spectroscopy. The crystal structure of 9 has been determined by X-ray diffraction analysis.     

The synthesis of di- and tetramethyl substituted macrocyclic polyether-diester ligands

Three series of macrocyclic polyether-diester ligands have been prepared from dimethyl triethylene glycol ( 20 ), two dimethyl tetraethylene glycols ( 21,23 ), dimethyl pentaethylene glycol ( 22 ) and tetramethyl tetraethylene glycol ( 24 ) and diglycolyl chloride (products 5–9 ), thiadiglycolyl chloride (products 10–14 ) and 2,6-pyridine dicarbonyl chloride (products 15–19 ). The eighteen-membered rings ( 6 and 16 ) formed solid potassium thiocyanate complexes. The eighteen- and twenty-one-membered ring compounds 6–8 and 16–18 complexed with benzylammonium perchlorate in methylene chloride-d₂ as shown by significant chemical shift changes in the ¹H nmr spectra.     

Synthesis of substituted aryl amidines from aminoacetonitriles

Aryl aminoacetonitriles are oxidized by NiO₂-H₂O or MnO₂ in the presence of a wide range of NH₂-containing compounds to afford aryl amidines, presumably via iminium intermediates. A ‘one-pot’ procedure for the preparation of heteroaryl amidines from N-containing heteroaryl halides through a process comprising sequential S_NAr substitution and oxidation has also been developed.     

Mass spectrometry of bis-quinolizidine alkaloids: 13-keto and hydroxy substituted derivatives of sparteine and lupanine

The mass spectral fragmeutations of 13-ketosparteine, 13-hydroxysparteine, 13-epihydroxysparteine, 13-ketolupanine, 13-keto-α-isolupanine, 13-hydroxylupanine, 13-hydroxy-α-isolupanine, 13-epihydroxylupanine and 13-epihydroxy-α-isolupanine are reinvestigated and discussed. Fragmentation pathways, elucidation of which was assisted by accurate mass measuiements and metastable transitions, are proposed. The fragmentation assignments are not consistent with those previously reported in the literature. Many fragment species of the same m/z (low-resolution spectra) are composed of two fragment ions of different elemental compositions (high-resolution spectra). The obtained data create a safe basis for distinguishing structural and stereoisomers.     

Gold-catalyzed rearrangement of substituted allyl aryl ethers

Triphenylphosphinegold(I) complexes catalyze the Claisen-type rearrangement of aryl allyl ethers to the corresponding branched and linear products. The product distribution depends on the olefin geometry of the allylic ether. Stereochemical transfer experiments support an ionic mechanism.     

Mass spectrometry of hop compounds—III. Mass spectra of substituted 1,3-cyclopentanediones derived from hop constituents

The mass spectra of isohumulones (IV, V), tetrahydroisocohumulones (VI, VII), tetrahydroisohumulones (VIII) neohydroisocohumulones (XI, XII) cohumulinic acid (III), lupuloxinic acid (XV), humulinone (XIV) and related compounds are described. Ions which appear to be diagnostic for particular structures are discussed.     

Mass spectrometry of nitroazoles 1–The mass spectra of methyl substituted nitropyrazoles

The mass spectra of all isomers of methylnitropyrazoles are reported. Generally, the spectra are characteristic of nitropyrazoles. In some cases however, ortho effects occur, recognizable by primary losses of, for example, OH^., H₂O, CHO^., CH₂O.