Synthetic studies on chemotherapeutics. II. Synthesis of phenyl-substituted 1,4-dihydro-4-oxonicotinic acid derivatives. [Studies on the syntheses of heterocyclic compounds. Part 704]

The thermal cyclization of the arninomethylenemalonates (8) gave the 4-hydroxynicotinates ( 9 ), ethylation of which yieldedN-ethylated ( 11 ) and O-ethylated products ( 12 ). Hydrolysis of 9, 11 , and 12 led to the desired nicotinic acids (10, 4, and 13), respectively.     

New organic activators for the enantioselective reduction of aromatic imines with trichlorosilane

N-Picolinoyl-(2S)-(diphenylhydroxymethyl)pyrrolidine was found to work as an organic activator in the reduction of aromatic imines to the corresponding amines by Cl₃SiH. The highest selectivity was 80% ee. These are the first data showing that N-formyl group is not always essential as N-protecting group of pyrrolidine derivatives for the reduction of imines by Cl₃SiH.     

Some chemical transformations of 7a-cyanohexahydro-1H-pyrrolizine into 7a-substituted hexahydro-1H-pyrrolizines

Chemical transformations of 7a-cyanohexahydro-1H-pyrrolizine ( 2 ) into 7a-substituted hexahydro-1H-pyrrolizines are described. In the reaction of 2 with lithium aluminum hydride, the orientation of the lone pair of the bridgehead nitrogen against C-CN bond can be regarded as significant.     

Studies on polymers from cyclic dienes. XII. Cationic polymerization of spiro[2,4]hepta-4,6-diene

Polymerizations of spiro[2,4]hepta-4,6-diene were carried out with cationic initiators and Ziegler-type catalysts. This monomer polymerized very rapidly with a variety of cationic initiators, and low monomer and initiator concentrations had to be employed in order to avoid formation of crosslinked polymers. The polymer contained 1,2 and 1,4 addition units, and there was no indication of the opening of the cyclopropyl ring in the monomer unit. The following relationship was obtained: [η] = 4.5 × 10^?8M?_n^1.71. The exponential coefficient of this equation is much greater than those typical of vinyl polymers, suggesting that the polymer chain is very stiff. The polymer showed much enhanced resistance to autoxidation as compared with polycyclopentadiene, and its softening point was above 200°C. These interesting physical and chemical properties of the monomer and the polymer can be associated with their spiro structures.     

Novel structural and magnetic properties of a 1-D iron(II)-manganese(II) LIESST compound bridged by cyanide

The 1-D compound [Fe(L)(CN)2][Mn(hfac)2] (1), which adopts the -NC-Fe-CN-Mn- heterometallic structure, has been shown to exhibit light-induced excited spin-state trapping effects. After illumination, anti-ferromagnetic coupling was observed between the iron(II) (S = 2) and manganese(II) (S = 5/2) ions.     

Control of photochemical, photophysical, electrochemical, and photocatalytic properties of rhenium(I) complexes using intramolecular weak interactions between ligands

Intramolecular interactions between ligands have been successfully applied as a novel tool for controlling various properties of a series of cis,trans-[Re(dmb)(CO)(2)(PR(3))(PR'(3))](+)-type complexes (dmb = 4,4'-dimethyl-2,2'-bipyridine), in the ground state and in the excited state and in the one-electron reduced form. For rhenium complexes with two triarylphosphine ligands, P(p-XPh)(3), the dmb ligand was sandwiched by four aryl rings having CH(aryl)-pi(pyridine)-pi(aryl) interactions. On the other hand, complexes with one triarylphosphine ligand and one trialkylphosphite ligand, P(OR)(3), had pi-pi and CH-pi interactions between each pyridine ring in the dmb ligand and the aryl group in the P(p-XPh)(3). Various properties of these two series of rhenium complexes were compared with those of complexes having two trialkylphosphite ligands, which do not interact through space with the dmb ligand. Properties of the complexes associated mainly with the dmb ligand are strongly affected by the intramolecular interactions: (1) UV/vis absorptions to the pi-pi and (1)MLCT excited states were both red-shifted, but (2) emission from the (3)MLCT excited state was blue-shifted; (3) the lifetime of the (3)MLCT excited state was prolonged up to 3-fold; (4) the reduction potential in the ground state was positively shifted by 110 mV with pi-pi and CH-pi interactions and by 180-200 mV with the CH-pi-pi interactions. (5) In the excited states, the oxidation power of the complex was also enhanced by the intramolecular interactions. (6) In the corresponding one-electron-reduced species cis,trans-[Re(dmb(-.)(CO)(2)(PR(3))(PR'(3))], the intramolecular interactions are maintained and strongly affected their UV/vis spectra. (7) Photocatalysis for CO(2) reduction was significantly enhanced only by the CH-pi-pi interaction.     

Studies on the syntheses of heterocyclic compounds. Part DCXII. A simple synthesis of benzopyran and dibenzopyran derivatives

trans-2-(3-Hydroxyphenyl)cyclohexanol (1b) was converted into 6-methyl-6-phenylbenzopyran (11a) and 6-spirocyclohexanobenzopyran (11b) by phenolic cyclization or under acidic condition. This type of reaction was also applied to the synthesis of 3,4-dihydro-6-methoxy-1-methoxycarbonyl-1-methyl-1H-2-benzopyran (IV).     

Geometrical shapes of molecules by iterative extended Hückel method

The iterative extended Hückel method proposed by Harriset al. has been employed to calculate the shapes of 21 molecules consisting of H, C, N, and O. It has given fairly reasonable results, especially when it has been combined with a new formula; the formula regards the orbital energies and the wave functions of the Hückel method as those of the Hartree-Fock method.     

Photo-oxygenations of 1H-azepine derivatives isolation and characterization of the [6+2] cycloaddition product

The reactions of 1H-azepine derivatives ($\text{1a-b}$ and $\text{4}$) with singlet oxygen gave the [6+2] cycloadducts ($\text{2a-b}$) and the [4+2] cycloadducts ($\text{3a-b}$ and $\text{5}$). The thermal and base-catalyzed rearrangements of the oxygen-adducts were investigated.     

SCF MO INDO calculation of anisotropie hyperfine coupling tensors for σ-type radicals

The anisotropic hyperfine coupling tensors for some -type radicals (HCO, FCO, NO₂, CO ₂ ^– , CN, phenyl, vinyl) were calculated. The calculation was performed with an all-valence-electron approximate open-shell MO method using the INDO approximation and with the dipolar integrals evaluated over Slater-type AO's. The diagonalyzed tensors were in reasonable agreement with the available data of experiment.