Tandem Cyclization of Alkynylmetals Bearing a Remote Leaving Group via Cycloalkylidene Carbenes

Treatment of terminal alkynes bearing a remote leaving group with MNR(2) (M = Li, Na, K) gives bicyclo[n.3.0]-1-alkenes (n = 3, 4). The tandem cyclization proceeds through a mechanism involving exo-cyclization of an alkynylmetal intermediate and intramolecular C-H insertion of the resulting carbenoid.     

A Facile Route to Indolo

Treatment of 1-(2'-bromobenzyl)-3,4-dihydroisoquinolines 2 in the presence of K(2)CO(3) in boiling DMF efficiently provided a variety of alkoxy-substituted indolo[2,1-a]isoquinolines 3. Application of this cyclization to 7-benzyloxyisoquinoline derivatives, followed by further elaboration of the resultant 2-benzyloxy-5,6-dihydroindolo[2,1-a]isoquinolines 16a,b, led to the formal synthesis of dibenzopyrrocoline alkaloids, (+/-)-cryptaustoline (1a) and (+/-)-cryptowoline (1b).     

Aryl radical cyclizations: one-Pot syntheses of protoberberine and pavine alkaloids

Treatment of 2-(2'-bromo-beta-phenethyl)isocarbostyrils 7 with AIBN-Bu(3)SnH in boiling benzene gave 8-oxoberbines 3 in good yields. A similar treatment of 2-(2'-bromo-beta-phenethyl)isoquinolinium bromides 6 and their nor- and homoanalogues (10,11) induced 6-, 5-, and 7-exo radical closures in a one-pot manner to give protoberberines 2, dibenzo[b,g]indolizidine 14a and, dibenzo[a, h]-1-azabicyclo[5.4.0]undecane 15a, respectively. A one-pot radical cyclization of 1-(2'-bromobenzyl)isoquinoline methiodide 18a gave a pavine alkaloid, (+/-)-algemonine (19a).     

A novel synthesis of (E)-3,7-dimethyl-2-octene-1,8-diol secreted by the african monarch using the ring-opening reaction of α-methyl-β-propiolactone

The regioselective ring-opening reaction of α-methyl-β-propiolactone with 3,3-ethylene-dioxybutylmagnesium bromide in the presence of copper(I) catalyst afforded 2-methyl-6-oxoheptanoic acid, which was easily converted into (E)-3,7-dimethyl-2-2-octene-1,8-diol in good yield.     

Sulfur-containing polymers. IV. Preparation and properties of poly(sulfenyl thiocarbonates)

Poly(sulfenyl thiocarbonates) have been prepared for the first time by the stepwise condensation of chlorocarbonylsulfenyl chloride with diols and dithiols. The polymers were obtained in high yield. Generally they were crystalline solids and were soluble in chlorinated hydrocarbons. On treatment with benzyl mercaptan in the presence of triethylamine, the polymers afforded a diol, carbonyl sulfide, and a disulfide compound. This reaction was extended to the preparation of alternating copolydisulfides.     

Analysis of anomalous vibrational and rotational distributions in the CN(B2Σ+) state produced in the reaction of Ar(3P0,2) metastables with BrCN

The CN(B²Σ⁺ - X²Σ⁺) tail band emission system for μ′ = 11–20 resulting from the energy transfer reaction Ar(³P_0,2) + BrCN in a flowing afterglow apparatus was measured. The vibrational and rotational distributions were determined as a function of argon pressure. Numerous perturbed rotational lines were observed; analysis of the dependences of these lines on argon pressure, with the aid of experimental information already published, led to the following assignments as to the origins of the perturbations: For μ′ = 11, N′ = 20 and μ′ = 13, N′ = 9, the perturbing state is a ⁴Σ⁺; for μ′ = 12, N′ = 10 and 14, μ′ = 14, N′ = 7 and 10, and μ′ = 17, N′ ≈ 17–19 the perturbing state is A ²Π_i. The perturbed rotational line, μ′ = 11, N′ = 20, is found to be the primary source of intensity in the μ′ =11 vibrational band, but in all other cases the perturbed rotational lines do not significantly aid in the populating of the vibrational state. The anomalously high vibrational populations found in the tail band emission system (μ′ = 12, 14, 17 and 18), as well as the significantly high rotational excitations observed in the μ′ = 12–20 vibrational bands, apparently arise directly from the reaction intermediate.     

Electric conductivity of TCNQ salts of ionene polymers containing triethylenediammonium or 4,4′-bipyridilium ring

The ionene polymers were prepared by the Menshutkin reaction of α,ω-dibromoalkane (n) with triethylenediamine (TDA) or 4,4′-bipyridil (BP). Resistivities (p) and activation energies of conduction (E_a) were measured for the polymeric 7,7,8,8-tetracyanoquinodimethan (TCNQ) salts with these ionenes. The correlation between the chemical structure of the ionenes and the conductivity was discussed. In the TDA,n-TCNQ complex salts and the BP,n-TCNQ simple salts the salts of the ionenes containing even numbers of CH₂ groups showed higher conductivities than those of the ionenes containing odd numbers of CH₂ groups. The conductivities determined by the narrower interval between the N⁺ cations of the main chains were measured in the simple salts. In the complex salts the conductivities determined by the larger interval were measured. The conformational change of the matrix ionenes affected the arrangement of the TCNQ molecules. The values of p were 79.7 and 12.5 Ω cm, and the values of E_a were 0.122 and 0.063 eV for TDA,4-TCNQ complex salt and BP,5-TCNQ complex salt, respectively.     

Organic homojunction diodes with a high built-in potential: interpretation of the current-voltage characteristics by a generalized Einstein relation

We realize p- and n-type doping of the organic semiconductor zinc-phthalocyanine using a novel strong organic donor. This allows us to demonstrate the first stable and reproducible organic p-n homojunctions. The diodes show very high built-in potentials, attractive, e.g., for organic solar cells. However, the diode characteristics cannot be described by the standard Shockley theory of the p-n junction since the ideality factor strongly increases with decreasing temperature. We show that this behavior can be explained by deviations from the Einstein relation for disordered materials.     

Electromagnetically induced diffraction in sodium vapor

By using a sodium atomic vapor we have observed a honeycomb-type multiple-diffraction pattern that was due to a grating induced optically by three noncollinear bichromatic excitation beams. In particular, when the two incident frequencies satisfy the two-photon resonance condition and the atomic density is high, the diffraction is enhanced by electromagnetically induced transparency, and strong Stokes and anti-Stokes components are generated in well-defined directions.     

In vivo quantification of the metabolites in normal brain and brain tumors by proton MR spectroscopy using water as an internal standard

Metabolite concentrations in normal adult brains and in gliomas were quantitatively analyzed by in vivo proton magnetic resonance spectroscopy (MRS) using the fully relaxed water signal as an internal standard. Between January 1998 and October 2001, 28 healthy volunteers and 18 patients with gliomas were examined by in vivo proton MRS. Single-voxel spectra were acquired using the point-resolved spectroscopic (PRESS) pulse sequence with a 1.5 T scanner (TR/TE/Ave = 3000 ms/30 ms/64). The calculated concentrations of N-acetyl-aspartate (NAA), creatine (Cre), choline (Cho), and water(H(2)O) in the normal hemispheric white matter were 23.59 +/- 2.62 mM (mean +/- SD), 13.06 +/- 1.8 mM, 4.28 +/- 0.8 mM, and 47280.96 +/- 5414.85 mM, respectively. The metabolite concentrations were not necessarily uniform in different parts of the brain. The concentrations of NAA and Cre decreased in all gliomas (p < 0.001). The NAA/Cho and NAA/H(2)O ratios can distinguish the normal brain from gliomas and low-grade from high-grade astrocytoma (p < 0.001). The concentration of taurine (Tau) in medulloblastomas was 29.64 +/- 5.76 mM. This is the first quantitative analysis of Tau in medulloblastoma in vivo and confirms earlier in vitro findings.