Enantiospecific Synthesis and Cytotoxicity Evaluation of Ligudentatol: A Programmed Aromatization Approach to the 2,3,4‐Trisubstituted Phenolic Motif via Visible‐Light‐Mediated Group Transfer Radical Cyclization

A facile enantiospecific approach to (+)‐ligudentatol ( 1 ) and (?)‐ligudentatol (ent‐ 1 ) is reported. The approach features the construction of a trisubstituted phenolic motif fused to a chiral aliphatic ring by a sequence of visible‐light‐mediated radical seleno transfer cyclization, bromination, concomitant selenoxide elimination–dehydrobromination, and demethoxycarbonylation, namely, a programmed aromatization. Biological evaluation of the enantiomers of ligudentatol obtained by the present route revealed for the first time their cytotoxicity towards various cancer cell lines.     

Novel network morphology of poly(p‐oxybenzoyl)

Polymerization of 4‐acetoxybenzoic acid (ABA) with 3,5‐diacetoxybenzoic acid (DABA) was examined to control the morphology of poly(p‐oxybenzoyl) (POB). Polymerizations were carried out at a concentration of 1.0% in an aromatic solvent Therm S‐1000® (mixture of dibenzyltoluene) at 320 °C. Polymerization of ABA yielded the POB fibrillar crystals, but the polymerization with DABA at a concentration in the feed (χ_f) of 0.10–0.15 afforded novel network structures comprised of spheres connected by fibrillar crystals. The diameter of the spheres prepared at χ_f of 0.15, which were 0.7 and 5.0 μm, showed bimodality. The network distance, fibril length, and fibril width were 6.1, 2.6, and 0.1 μm, respectively. They possessed high crystallinity. The network structure was formed as follows. Co‐oligomers were first precipitated in the beginning of the polymerization by liquid–liquid phase separation to form the microdroplets. The fibrillar crystals were formed in the coalesced spheres by the crystallization of oligomers induced by the increase of molecular weight. The fibrillar crystals connecting the spheres gradually appeared owing to the shrinkage of the spheres. The fibrillar crystals grew from the surface of the spheres with the crystallization of homo‐oligomers of 4‐oxybenzoyl units, and finally the network structure was completed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1624–1634, 2005     

Ammonium hydrogen tartronate at 240 and 20 K

The low-temperature structure determination of the title compound, alternatively called ammonium hydrogen hydroxy­propane­dioate, NH₄⁺·C₃H₃O₅⁻, has revealed that the H atom involved in a very short asymmetric O—H⋯O hydrogen bond [O⋯O = 2.448 (2) Å at 240 K and 2.4393 (10) Å at 20 K] is disordered.     

Oxidative decarboxylation of cyclic amino acids and dehydrogenation of cyclic secondary amines with iodosobenzene

Cyclic amino acids L-proline, pipecolinic acid and L-2-pyrrolidinone-5-carboxylic acid undergo oxidative decarboxylation with iodosobenzene in various solvents (including water) to yield the lactam and imide in the latter case. The reaction proceeds via initial imine formation.     

Nanoflow system for perfect regiocontrol in the Baeyer-Villiger oxidation by aqueous hydrogen peroxide using lowest concentration of a fluorous lanthanide catalyst

The scandium bis(perfluorooctanesulfonyl)amide-catalyzed Baeyer-Villiger reaction significantly increased the regioselectivity as well as the reaction rate by nanoflow system continuously controlled by a nanofeeder even in the lowest concentration of the catalyst (?0.1 mol %). The Baeyer-Villiger reaction completed within few seconds as a contact time in the microcell to afford the lactone products high regioselectively without hydrolysis.     

Double C-H functionalization in sequential order: direct synthesis of polycyclic compounds by a palladium-catalyzed C-H alkenylation-arylation cascade

Palladium-catalyzed cascade C-H alkenylation and arylation provides convenient access to polycyclic aromatic compounds. Treatment of 3-bromoaniline derivatives bearing a bromocinnamyl group on the nitrogen atom with a catalytic amount of [Pd(OAc)(2)] and PCy(3)·HBF(4) in the presence of Cs(2)CO(3) in dioxane affords naphthalene-fused indole derivatives in good yields. This double cyclization reaction is also applicable to heterocyclic substrates, giving fused indoles containing a heteroaromatic ring such as dibenzofuran, dibenzothiophene, carbazole, indole, or benzofuran through heterocyclic C-H arylation. When using a 2,6-unsubstituted aniline derivative, the first C-H arylation preferentially proceeds at the more hindered position of the aniline ring.     

Intramolecular iron(II)-catalyzed aminobromination of allyl N-tosyloxycarbamates

Allyl N-tosyloxycarbamates are found to be catalytically transformed into β-brominated oxazolidinones with FeBr(2)/n-Bu(4)NBr in t-BuOH.     

Polarized ethylenes. IV. Synthesis of polarized ethylenes using thioamides and methyl dithiocarboxylates and their application to syntheses of pyrazoles,pyrimidines, pyrazolo[3,4-d]pyrimidines,and 5-aza[2.2.3]cyclazines

Polarized ethylenes having both electron-donating (an amino or a methylthio group) and electron-accepting (cyano, carbamoyl, methyl ester) groups on the adjacent two olefinic carbon atoms were prepared by the condensation of S-alkylthioamidinium salts or methyl dithiocarboxylates with the corresponding active methylene compounds in good yields. These polarized ethylenes were alternatively synthesized by the reaction of thioamides or methyl dithiocarboxylates with tetracyanoethylene oxide in good yields. Reactions of these polarized ethylenes with hydrazine or guanidine derivatives occurred smoothly to give the corresponding pyrazole and pyrimidine derivatives in good yields. The synthesis of 5-aza[2.2.3]cyclazine derivatives using polarized ethylenes is also described.     

Facile palladium(0)-catalyzed ring expansion reactions of hydroxy methoxyallenyl cyclic compounds via hydropalladation

Palladium(0)-catalyzed one-atom ring expansion of various hydroxy methoxyallenyl compounds has been achieved in excellent yields without the use of aryl halides. Hydroxy methoxyallenylisoindolinones, -indanones, and -phthalans have been readily converted to the corresponding isoquinolones, naphthoquinones, and isochromanones in the presence of P(o-tolyl)(3).     

Hydroxyalkylation of alpha-C-H bonds of tetrahydrofuran with aldehydes in the presence of triethylborane and tert-butyl hydroperoxide

The alpha-hydroxyalkylation of tetrahydrofuran with aldehydes via radical C-H abstraction was conducted using triethylborane in the presence of tert-butyl hydroperoxide. This study presents a rare instance of direct intermolecular radical addition of unactivated cyclic ether to aldehydes.