Search

The article discusses the natural occurrence, syntheses and applications of various 3,4- and 4,5-methanoamino acids. These acids are found to be of great significance in the pharmaceutical industry.

The article explains the natural occurrence, syntheses and the applications of 1-aminocyclopropanecarboxylic acid and various other cyclopropyl-group-containing [alpha]-amino acids.

The cycloadditions of diazene derivatives onto 2-arylcyclopropane-1, 1-dicarboxylates which formed the pyrazolidine derivatives, in presence of Ga[Cl.sub.3] catalyst is demonstrated.

A new class of polcyclic aromatic hydrocarbons - oligoindenopyrenes was prepared featuring a Pd-catalyzed Suzuki-Heck coupling cascade. It is observed that after excitation, the tetraindenopyrene derivative 3d undergoes efficient deactivation (99%) by internal conversion to the ground state and the small fluorescence quantum yield (0.004) is in accordance with the short ( 0.6 ns) fluorescence decay time.

The microwave (MW) spectra of (methylenecyclopropyl)methanol (H2C=C3H3CH2OH) and one deuterated species (H2C=C3H3CH2OD) are investigated in the 20-80 GHz spectral range and the spectra of two rotameric forms, conformer I and conformer IX are assigned. The MW spectroscopy is an ideal experimental method to examine conformational equilibria, whereas quantum chemical calculations are performed as they are a useful aid in the assignment procedure of complex MW spectra.

The study clarifies whether configurationally repetitive oligyocyclopropanes adopt repetitive conformations such as those of istotactic polymers. The helix with equal handedness shown in the stereopicture is found for tercyclopropanedimenthanol.

Research has been conducted on the methylenecyclopropane, bicyclopropylidene and spirocyclopropanated methylenecyclopropanes. The bromine additions to these compound carried out in methanol have been investigated and the results indicate the enhanced bromination rate with the increased number of spiroannelated three-membered rings.

Isolable quantities of [C.sub.60], the smallest stable fullerene, have been synthesized in 12 steps from commercially available starting materials by rational chemical methods. A molecular polycyclic aromatic precursor bearing chlorine substituents at key positions forms [C.sub.60] when subjected to flash vacuum pyrolysis at 1100 ° C. No other fullerenes are formed as by-products. The methods we have developed for the target-specific synthesis of fullerenes, applied here to a synthesis of [C.sub.60], should make possible the directed laboratory preparation of other fullerenes as well, including those not accessible by graphite vaporization., Although [C.sub.60] and some of the higher fullerenes can be readily prepared by resistive heating of graphite (1), there is still considerable interest in the rational stepwise synthesis of these [...]

The chemical 1-amino-1-ethenylcyclopropane is investigated for its behaviour when subjected to microwaves and the resulting gases recorded for conformity and structure.

The reaction between tribenzotriquinacene (R = H) and its centro-alkyl-substituted derivatives (R = Ch3, C2H5, CH2Ph) with the highly basic n-BuLi and KOtPen mixture results in the formation of tribenzacepentalene dianion (5-K2). The reaction involves a 2-fold deprotonation and the removal of RH from locations C(1)-C(10). Trapping 5-K2 with various electrophiles generates 4,7-disubstituted tribenzodihydroacepentalenes.

The propensity of bicyclopropylidene in a CF3CCL3 matrix rearrangement to that of tetramethyleneethane depends on the Freon matrix used. The secondary paramagnetic species is also matrix-dependent. Bicylopropylidene provides a paradigm for oxidation of a small organic molecule in a 3-fold way. The molecules containing three-membered rings register structural changes upon ionization. The strained rings in radical cations undergoing thermally or photolytical isomerization rearrange by ring openings.

A study was done on the nucleophilic substitutions of 1-alkenylcyclopropyl esters and alkenylcyclopropyl chlorides catalyzed by palladium. Results show that 1-ethynelcyclopropyltosylate and cyclopropylideneethyl acetate and carbonate can be substituted with a variety of of nucleophiles in the presence of palladium catalysts without ring opening and with complete regioselectivity.