Novel annulene dications from methylated [2.2]metacyclophane monoenes and [e]-ring benzannelated dimethyldihydropyrene

Tetramethyl- and hexamethyl-substituted [2.2]metacyclophane monoenes (10 and 11) are transformed into their corresponding trans-dimethyldihydroethanophenanthrenium dications (14(2+) and 15(2+)) in FSO(3)H x SbF(5) (4:1) and FSO(3)H x SbF(5) (1:1) with SO(2)ClF or SO(2) as the solvent; these 10 pi-dications are equivalent to the C-4/C-5 diprotonated dications of the 2,7-dimethyl derivative of trans-DMDHP, 3a. The trans-12c,12d-dimethyl-12c,12d-dihydrobenzo[e]pyrene (6) reacts with FSO(3)H/SO(2)ClF under surprisingly mild conditions to give initially a persistent diprotonated dication (6H(2)(2+)) and, subsequently, the oxidation dication (6(2+)); the 6(2+):6H(2)(2+) ratio reaches 4:1 after 1 week at low temperature. Protonation of the anti-metacyclophane (13) was also examined. Charge delocalization mode and tropicity in the resulting dications are gauged via detailed NMR studies at 500 MHz.     

Insertion of pyridine into an iron-silicon bond: structure of the product Cp*(CO)Fe[eta3(C,C,C)-C5H5NSiMe2NPh2

Heating a toluene solution of Cp*(CO)(C5H5N)FeSiMe2NPh2 led to insertion of pyridine into the iron-silicon bond to form Cp*(CO)Fe[eta3(C,C,C)-C5H5NSiMe2NPh2].     

Chemistry of the neopolyoxins,pyrimidine and imidazoline nucleoside peptide antibiotics

New chitin synthetase inhibitors, neopolyoxins A, B, and C were isolated from the culture filtrate of Streptomyces cacaoi subsp. asoensis. Their absolute structures have been established on the basis of chemical and spectroscopic evidence. They are structural analogs of the polyoxins. As a nucleobase, neopolyoxin C possesses uracil, while neopolyoxins A and B contain the imidazoline moiety. A ring contraction reaction of pyrimidine nucleoside into imidazoline nucleoside played a key role in the structure determination of the nucleoside moiety. A similar transformation was suggested for the biosynthesis of neopolyoxins A and B.     

Electron spin relaxation of some alkane cation radicals as an indicator of dynamics between the distorted structures

ESR saturation phenomenon was observed for various alkane cation radicals derived from cyclohexane, propane and norbornane in frozen halocarbon matrices at 4 K. In addition to spectral diffusion by spin-spin interaction between the radicals, which is a common mechanism of ESR relaxation in the solid state, isotropic hyperfine modulation by the dynamics between the equivalent distorted structures was found to be very important for those centers which show Jahn-Teller (JT) or pseudo-JT effects. The effect of annealing of the sample at 77 K is also discussed.     

Fluorinated polysilanes. Palladium catalyzed 1,4-addition of fluorodisilanes to conjugated diene and enone systems

In the presence of palladium complexes as catalysts, fluorinated disilanes add to 1,3-dienes, metehyl vinyl ketone and p-benzoquinone to give mainly 1,4-addition products.     

Carbazoledioxazines having long alkyl groups. 2. Synthesis of carbazoledioxazines with angular type structure

Carbazoledioxazines with an angular type structure (5,15-dialkyl-7,17-dialkyloxy-9,19-dichloro-5,15-dihydrodiindolo[2,3-c:2′,3′-n]triphenodioxazines) were selectively synthesized by electrochemical oxidative ring closure of precursors (2,5-bis(9-alkyl-2-alkyloxy-3-carbazolylamino)-3,6-dichloro-1,4-benzoquinones). The structure was confirmed by ¹H-nmr and other instrumental analyses. Their thermal properties and solubilities were investigated and were compared with those of carbazoledioxazines with a linear type structure.     

Dynamic stability of carbonyl ylides

The non- and fluorine-substituted singlet carbonyl ylides are studied by using ab initio MCSCF calculations. The thermodynamic stability of the carbonyl ylides and the intramolecular stability to isomerization or fragmentation reaction coordinates is demonstrated in terms of the topological structure of the ab initio potential energy surfaces. The allylic resonance is found to be dynamically unstable, considering out-of-plane vibrational mode. The instability is studied by the symmetries of the low-lying excitations out of the MCSCF wave function.     

Theoretical study of the electronic structure of the lower states of the [Cr2Cl9]3- and [Mo2Cl9]3- ions

The electronic structure of the lower states of a trigonal Cr3+ pair and Mo3+ pair, which occur in the Cs3M2Cl9 crystal (M=Cr,Mo), were studied by theoretical calculations carried out according to several methods: multireference singly and doubly excited configuration interaction, second-order configuration interaction, and multireference coupled-pair approximation. We employed a model of a [M2Cl9]3- anion embedded in a cage of point charges, which were arranged so as to simulate the anion in the crystal. The model core potential was utilized, where the relativistic effect was included for Mo. Results of the Cr complex showed that there were no direct bonds between the Cr metals. The lower electronic spectra of the [Cr2Cl9]3- ion were interpreted in terms of the electronic spectra of [CrCl6]3-. The lowest state of simultaneous excitation in both metals was considered. The [Mo2Cl9]3- ion exhibited a single direct bond between the metals. Reflecting this single bond, the observed singlet-triplet splitting was much larger than that in the case of Cr and the calculated splitting was in good agreement with the observed one. We account for the electronic spectra of the [Mo2Cl9]3- complex, which exhibited quite different features in the electronic excitation spectra in comparison with those of the Cr complex.     

Ion pairs in trifluoroacetolysis of 2-arylethyl arenesulfonates

The behavior of ion pairs in the trifluoroacetolysis of 2-arylethyl arenesulfonates was studied by means of tracer techniques with deuterium and oxygen-18.