Synthesis, resolution and applications of 3,3′-bis(RO)-MeO-BIPHEP derivatives

A series of optically pure 3,3′-bis(RO)-MeO-BIPHEP derivatives are prepared and used in palladium catalyzed asymmetric transformations. The phosphine oxide of (±)-5 is prepared in four steps from p-methoxyphenol and resolved using the novel resolving reagent chloro(l-menthoxy)dimethylsilane. Subsequent conversions provide catalysts 8 and 9. Ligands 6, 7 and 10 are prepared in six steps from p-methoxyphenol and the phosphine oxides of 6 and 7, and 10 are resolved using di-p-toluoyl- and dibenzoyl-l-tartaric acid, respectively. (R)-3,3′-Bispivalate 8 is superior to the other catalysts in asymmetric Heck reaction with 2,3-dihydrofuran while (R)-(+)-bis(tolyloxy) 10 and (+)-(R)-sugar derivative 9 are better in the Pd-catalyzed polyene cyclization; however, the absolute sense of chirality in the product from the polyene cyclization was reversed to that obtained when (R)-(+)-BINAP and (R)-(+)-MeO-BIPHEP were used.     

Stereochemical Aspects of the Beckman Rearrangement of Oximes of Levoglucosenone and Its Dihydro Derivative. Enantioselective Synthesis of (+)-γ-Pelargonolactone

Regiospecific C⁵5 -halogenation with retention of configuration occurred upon Beckman fragmentation of levoglucosenone oxime using SOCl₂ or PBr₃. On the other hand, the oxime of its dihydro derivative gave under these conditions the C⁶ - substitution product. A stereoselective synthetic scheme for (+)--pelargonolactone, an attractant for the rice and corn weevils Sitophiltus zeamais, was developed from the fragmentation product of levoglucosenone oxime.     

3-(Benzimidazolyl-2)-2-iminocoumarins in Reactions with Aromatic Aldehydes

Interaction of 3-(benzimidazolyl-2)-2-iminocoumarins with aromatic aldehydes in the presence of piperidine gave the corresponding 7-aryl-7H-benzo[4,5]imidazo[1,2-c]benzopyrano[3,2-e]pyrimidines. The 3-diethylamino derivatives of this series fluoresce effectively in alcohol solutions.     

Three possible products from the reactions of gewald's amide with aromatic aldehydes

Transformations of 2‐amino‐4,5,6,7‐tetrahydrobenzo[b]thiophene‐3‐carboxamide (Gewald's amide) in the reactions with aromatic aldehydes were studied. Efficient methods for synthesis of three possible types of products: 2‐aryl‐5,6,7,8‐tetrahydro[1]benzothieno[2,3‐d]pyrimidin‐4(3H)‐one, 2‐(1‐arylmethylidene‐amino)‐4,5,6,7‐tetrahydrobenzo[b]thiophene‐3‐carboxamide and 2‐aryl‐2,3,5,6,7,8‐hexahydro[1]benzo‐thieno[2,3‐d]pyrimidin‐4(1H)‐one derivatives were developed. All the products were easily isolated by filtration in very good overall yields. Mutual transformations of these compounds were also studied.     

Rapid formation of chemical complexity via a modified Biginelli reaction leading to dihydrofuran-2(3H)-one spiro-derivatives of triazolo[1,5-a]pyrimidine

The regio- and stereoselective, catalyst-free multicomponent synthesis of spiro-conjugated dihydrofuran-2(3H)-one/triazolo[1,5-a]pyrimidine derivatives in good to high yields via a Biginelli approach starting from ortho-substituted benzaldehydes, 3-amino-1,2,4-triazole and α-acetylbutyrolactone is reported. A plausible reaction mechanism for this transformation is discussed. The obtained heterocycles possess a drug-like conformationally restricted structure with defined stereochemistry and increased stability compared to other products obtained by this mode of the Biginelli reaction.     

Studying Conditions for Measuring an Analytical Signal on a PU-2 Polarograph

Conditions for measuring an analytical signal on a superuniversal PU-2 polarograph were studied using direct-current, normal-pulse, differential-pulse, alternating-current square-wave, alternating-current sine-wave, and rapid potential sweep voltammetry modes. Dropping-mercury, static dropping-mercury, mercury–graphite, and gold–graphite electrodes were examined with a linear, triangular, and pulse potential sweep. It was demonstrated that the alternating-current square-wave mode, which can be combined with a triangular potential sweep, possesses the best sensitivity.     

Influence of the dopant type on point defects in PbMoO4 crystals

Nominally pure and Nd³⁺-doped single crystals of PbMoO₄ grown by the Czochralski method with the use of Nd₂O₃, Nd₂(MoO₄)₃, NaNd(MoO₄)₂, and NdNbO₄ compounds are investigated by the methods of single-crystal and powder X-ray diffraction analysis, single-crystal neutron diffraction, and impedance spectroscopy. The types and concentration of point defects are determined. Their effect on the dielectric properties of crystals is hypothesized. It is established that the color of the crystals is caused by the formation of color centers.