Mass spectra of new groups of functionalized heterocycles

The influence of the position and nature of the substituent in the thiophene ring on the fragmentation of 3-alkyl- and 5-alkyl-2-thienylamines under electron impact was studied. The derivatives containing the ethyl group in position 3 decompose due to both the elimination of the fragments from the substituents and thiophene ring rupture. In the case of the compounds with thetert-butyl group in position 5, the last process is not observed. The fragmentation of the 3- and 5-methyl-substituted derivatives occurs mainly from the isomeric thiopyran form of the molecular ion. For Part 2, see Ref. 1. Deceased. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1560–1563, September, 2000.     

New Approach to the Synthesis of Strained Cyclic Systems: I. Iminocyclobutenes and Iminothietanes from 1,3-Dilithio-3-phenylpropyne and Methyl Isothiocyanate

The reaction of 1,3-dilithio-3-phenylpropyne with methyl isothiocyanate in THF-hexane at -90 to -55°C, followed by successive treatment of intermediate product with a donor of protons, superbase, and alkyl halide, yields isomeric iminocyclobutenes and iminothietanes in addition to the expected aminothiophene. The ratio of the products depends on the amount and nature of proton donor (MeOH, t-BuOH), base (MeONa, t-BuOM, M = Li, Na, K; t-AmOK), co-solvent (DMSO, HMPA), and alkyl halide (MeI, EtI, BuBr). The system t-BuOH(MeOH)-t-BuOK-DMSO is the most favorable for the formation of the corresponding iminocyclobutene.     

Synthesis and oxidative cleavage of poly(trimethylene diselenides)

1-Bromo-3-chloropropane and elemental selenium react in hydrazine hydrate-alkali and hydrazine hydrate-amine systems to form poly(trimethylene diselenides). The reductive cleavage of the resulting selenokols yielded 1,3-propanediselenol, 1,2-diselenolane, and bis(alkylseleno)propanes. These compounds are important reagents for organic synthesis and ligands for complex formation. The products obtained were studided by GC-MS.     

Ab Initio Study of the Acetylene–Allene Rearrangement in 2-Propargylpyrrole, 2-Propargylfuran, and 2-Propargylthiophene

Ab initio (MP4/6-31G*//RHF/6-31+G*) calculations have been performed to study the acetylene–allene rearrangement in X–CH₂–CCH propargyl systems, where X = ethenyl, E-1-butadienyl, 2-pyrrolyl, 2-furanyl, and 2-thienyl. The spatial and electronic structures, as well as the relative stability, of the initial and final acetylene structures and the corresponding allenes are examined. Migration of the triple bond from the terminal position into the chain, including the stage of allene structure formation, is shown to be thermodynamically favorable for the whole series of compounds. The propargyl substituents of heterocycles isomerize as readily as open diene systems. The differences in the isomerization energies in the series of allenyl- and 1-propynyl-substituted pyrrole, furan, and thiophene are mainly due to the differences in the nature of long-range interactions between heteroatoms and the tricarbon system.     

1-Silantranyl nitrate

A method of synthesis of 1-silatranyl nitrate O₂NOSi(OCH₂CH₂)₃N based on the reaction of 1-hydrosilatrane with mercury nitrate in the acetonitrile medium was developed. The structure of the synthesized 1-silatranyl nitrate, mp 227°C, was confirmed by elemental analysis, ¹H, ¹³C, and ²⁹Si NMR spectoscopy, infrared spectroscopy, and mass spectrometry. Silatranyl nitrate previously described in the literature as yellowish viscous oil apparently contains impurities preventing its crystallization.     

Reaction of tellurium with dichloromethane in the system hydrazine hydrate-alkali

Tellurium reacts with dichloromethane in the system hydrazine hydrate-alkali substituting one chlorine atom by tellurium whereas the second chlorine atom undergoes reductive substitution by hydrogen leading to the formation of methyltellanyl derivatives. Tentative mechanism of reduction is discussed. The discovered reaction allows the preparation of organotellurium compounds containing the MeTe group, including those involving other chalcogens.     

Intramolecular O → Si donor-acceptor interaction in R2P(=O)CH2CH2SiF3 molecules: Synthesis of dialkyl [2-(trifluorosilyl)ethyl]phosphonate and bis[(chloromethyl)dimethylsilyl] styrylphosphonate

The reaction of diethyl [2-(triethoxysilyl)ethyl]phosphonate with boron trifluoride etherate was used to synthesize diethyl [2-(trifluorosilyl)ethyl]phosphonate. The reaction of bis(trimethylsilyl) styrylphosphonate with chloro(chloromethyl)dimethylsilane gave bis[(chloromethyl)dimethylsilyl] styrylphosphonate. Multinuclear ¹H, ¹³C, ¹⁹F, ²⁹Si, and ³¹P NMR spectroscopy established the absence of a P=O → Si coordination bond in these compounds and the four-coordinate state of the silicon atom. Evidence for this finding was obtained by B3LYP/6-31G(d) quantum-chemical calculations. However, the same calculations for R₂P(=O)· CH₂CH₂SiF₃ (R = Me, Me₂N) showed the presence in such molecules of an O → Si coordination bond both in the gas phase and in CHCl₃ solution. The distance between the O and Si atoms in this series molecules decreases with R in the order: MeO > Me > Me₂N. The axial Si-F bond length increases in the same order and parallels the order of the Hammet σ ₀ ^m constants of these substituents, relating to their interaction with π-electron systems.     

N-Isopropenylazoles: I. Direct N-Isopropenylation of Azoles with Propyne and Allene

A number of previously unknown N-isopropenyl-substituted pyrroles, indoles, and di- and -triazoles were synthesized in 20-86% yield by reaction of the corresponding azole with an equilibrium mixture of propyne with allene or pure propyne and allene in the system KOH-DMSO (105-145°C, 5-15 h, atmospheric or elevated pressure). The reaction is regioselective. The electronic and steric structure and the degree of conjugation between the exocyclic double bond and the azole ring are discussed on the basis of the ¹H and ¹³C NMR spectra. Almost complete absence of p- conjugation in ,'-disubstituted N-isopropenylazoles have been found.