Synthesis of Fullerenes from a Nonaromatic Chloroform through a Newly Developed Ultrahigh-Temperature Flash Vacuum Pyrolysis Apparatus

The flash vacuum pyrolysis (FVP) technique is useful for preparing curved polycyclic aromatic compounds (PAHs) and caged nanocarbon molecules, such as the well-known corannulene and fullerene C60. However, the operating temperature of the traditional FVP apparatus is limited to ~1250 °C, which is not sufficient to overcome the high energy barriers of some reactions. Herein, we report an ultrahigh-temperature FVP (UT-FVP) apparatus with a controllable operating temperature of up to 2500 °C to synthesize fullerene C60 from a nonaromatic single carbon reactant, i.e., chloroform, at 1350 °C or above. Fullerene C60 cannot be obtained from CHCl3 using the traditional FVP apparatus because of the limitation of the reaction temperature. The significant improvements in the UT-FVP apparatus, compared to the traditional FVP apparatus, were the replacement of the quartz tube with a graphite tube and the direct heating of the graphite tube by impedance heating instead of indirect heating of the quartz tube using an electric furnace. Because of the higher temperature range, UT-FVP can not only synthesize fullerene C60 from single carbon nonaromatic reactants but sublimate some high-molecular-weight compounds to synthesize larger curved PAHs in the future.

Carbon subsulfide C3S2 – synthesis by flash vacuum pyrolysis and crystal structure determination

Carbon subsulfide C3S2 can be produced on a preparative scale by flash vacuum pyrolysis (FVP). The precursor 5-(methylthio)-3H-1,2-dithiole-3-thione (C4H4S4) proved to be particularly suitable and yields up to 8% could be achieved on evaporation at T = 180 °C and pyrolysis of the vapour at 950 °C. The other precursors tested, C4S6 and C6S8, were far less productive. Insight into the thermal conversion of C4S6 was gained by isolation and structure determination of a new isomer of the sulur-carbon compound C8S8, which is formed on thermal treatment of C4S6 at T = 330 °C. The formation of C8S8 can be interpreted by sulfur cleavage from C4S6. Crystal growth by sublimation below 0 °C allowed for the determination of the crystal structure of C3S2. The five-atomic molecules are linear and arranged in a typical pattern analogous to the crystal structures of I2, CS2 and CSe2. The reaction of C3S2 with bromine is known to give C3Br6S2 of yet unknown structure. By sublimation of C3Br6S2 in air, 4,5-dibromo-1,2-dithiol-3-one (C3Br2OS2) was obtained, representing the product of bromine abstraction and oxidation. This substantiates the former suggestion for C3Br6S2 to have the structure of a hexabromodithiolane.

Functionalized Allenes: Generation by Sigmatropic Rearrangement and Application in Heterocyclic Chemistry

The present review article summarizes the synthesis of allenes, which bear an adjacent functional group, by [3,3]- or [2,3]-sigmatropic rearrangement of appropriate propargyl substrates. Functionalized allenes, such as allenyl isothiocyanates, isoelenocyanates, isocyanates, thiocyanates, azides, azo compounds and others, are easily available by these methods. In several cases, however, the title compounds show high reactivity, which leads to rapid intermolecular or intramolecular successive reactions. Consequently, synthesis of the allenes by sigmatropic rearrangement has to be combined with special techniques, for example, flash vacuum pyrolysis or in situ generation and trapping reactions. The high tendency of the presented functionalized allenes to undergo cyclization reactions can be utilized to prepare heterocyclic products, for instance, thiazoles, selenazoles, 1,2,3-triazoles and pyrazoles. The synthesis of functionalized 1,3-butadienes by a second sigmatropic rearrangement of the title compounds is also successful.

A novel pathway for the thermolysis of N-nitrosoanthranilates using flash vacuum pyrolysis leading to 7-aminophthalides

Flash vacuum pyrolysis of N-methyl-N-nitrosoanthranilate esters offers a solvent-free route to 7-(methylamino)phthalides via a disproportionation pathway.

Nitrogen- and Sulfur-Containing Energetic Compounds. 64 Years of Fascinating Chemistry

This essay details the author’s work with high-energy molecules based on sulfur or nitrogen, or both, which started with amateur rocket propellants like zinc dust and sulfur followed by experiments with the highly sensitive compounds nitrogen trichloride and fulminating gold. Research on the inorganic and organic fulminates and the isomeric cyanates led to detailed investigations of reactive intermediates generated by flash vacuum pyrolysis or photolysis, in particular nitrenes and carbenes derived from azides, diazo compounds, triazoles, and tetrazoles and characterized in low temperature matrices.