Gohfu Suzukamo

Asymmetric reduction of oxime ethers. Distinction of anti and syn isomers leading to enantiomeric amines

Abstract Anti and syn ketoxime ethers were reduced with a chiral reducing agent prepared from (−)-norephedrine and 2 eq of BH 3 to give S and R amines respectively in up to 92% ee. The preferred absolute configuration of the amine was depended on the geometry of the oxime ether.

Stereoselective synthesis of anti-PAF active thiazolidin-4-ones via cyclo-condensation of alkyl α-mercaptocarboxylates with arylimines

Abstract Two distinctive methods for the synthesis of cis - and trans -2, 5-disubstituted-thiazolidin-4-ones via stereoselective cyclo-condensation between α-mercaptocarboxylic esters and arylimines have been developed. With the new reaction used as the key step, two sets of optically active anti-PAF active thiazolidin-4-ones were synthesized.

A practical convenient homogeneous palladium-phosphine catalysis for hydrocarbonylation of chlorobenzenes

Abstract Significant catalytic activity as well as high selectivity of benzoic acid has been found for hydrocarbonylation of chlorobenzene by using a catalyst system composed of PdCl2(PCy3)2K2CO3 aqueous solution-triethylamine (Cy: cyclohexyl).

C3 epimerization and selective C2C3 bond fission of alkyl chrysanthemate

Abstract Treatment of alkyl chrysanthemate with Lewis acid leads to C 3 epimerization, while protonic acid treatment gives rise to selective C 2 C 3 bond cleavage. The latter method is successfully applied to the synthesis of optically active tetrahydrolavandulol.

Asymmetric synthesis of a chroman derivative (vitamin e precursor)

Abstract Chromanmethanol 2 , a chiral intermediate for the synthesis of α-tocopherol 1 , is prepared from α-hydroxy aldehyde 5 , which is obtained by an asymmetric synthesis in over 95% ee.

A novel synthesis of α- and β-halonaphthalenes via regioselective ring cleavage of aryl(gem-dihalocyclopropyl)methanols and its application to total synthesis of lignan lactones, justicidin e and taiwanin c

Acid treatment of two types of aryl(gem-dihalocyclopropyl)methanols (ADCM) 1 gave α- and β-halonaphthalenes in good yields with excellent selectivity. With the new method used as the key step, the two title natural lignan lactones were synthesized in seven steps.

A synthesis of 4,7-dihydro-1H-dipyrrolo[3,2-b:2′,3′-d]pyrrole and 4,7-dihydro-4H-thieno[3,2-b]pyrrolo[2,3-d]pyrrole systems

Abstract The titled two systems ( 3 and 6 ), both new members of linearly fused heteroaromatics, were prepared using pyrrolo-annulation reaction: condensation of an aromatic aldehyde with azidoacetate followed by thermolysis of the resulting azidoacrylate.

Characterization of solid superbases prepared from γ-alumina and their catalytic activity

Abstract Solid superbases possessing basic sites stronger than H− = 37 have been prepared from γ-alumina by treatment with alkali metal hydroxides and subsequently with alkali metals. These solid superbases have been characterized by X-ray photoelectron spectroscopy, time-of-flight secondary ion mass spectrometry and X-ray absorption fine structure. Aluminate has been found to be formed on γ-alumina by treatment with alkali metal hydroxide and was supposed to have cationic vacancies. The alkali metal subsequently added to the aluminate is thought to occupy the cationic vacancies and be ionized, introducing electrons to the surface oxygen atoms. The oxygen atoms with increased negative charge are assumed to have an electron pair donating ability strong enough to exhibit superbasicity.

Palladium(ii) catalyzed thiono-thiolo rearrangement of propargyl thionophosphates

Abstract Palladium(II) effectively catalyzes the [3,3]-sigmatropic type rearrangement of propargyl thionophosphates to provide allenyl thiolophosphates specifically.

Efficient synthesis of 2,3-dimethylbutenes by dimerization of propylene using nickel-phosphine catalyst in the presence of strong sulfonic acids and/or dialkyl sulfates. Remarkable effect of strong sulfonic acids and/or dialkyl sulfates

Abstract Remarkable catalytic activities as well as high selectivities have been found for dimerization of propylene catalyzed by the nickel-phosphine system composed of nickel naphthenate/P(cyclo-C 6 H 11 ) 3 /AlEt 3 /2,4,6-trichlorophenol (TCP) especially in the presence of strong sulfonic acids (CF 3 SO 3 H, MeSO 3 H) or dialkyl sulfates (Me 2 SO 4 and Et 2 SO 4 ). The catalytic activity was further increased upon the combination of these effective additives. The desired C 6 olefins such as 2,3-dimethylbut-1-ene (DMB-1), 2,3-dimethylbut-2-ene (DMB-2, TMEN) could be obtained in relatively high yields by using these catalysts (selectivity of dimers = 70–80%: selectivity of dimethylbutenes in C 6 olefins = ∼80%). The ratio of DMB-1/TMEN could be controlled without changing the catalytic activities by varying the molar ratios of catalyst precursors. CF 3 SO 3 H was found to be the most effective additive for increasing the reaction rate, although the selectivity of dimethylbutenes decreased significantly. Addition of a small amount of water enhanced the reaction rate significantly (turnover numbers for 2,3-dimethylbutenes: 7046 → 30358). The importance of these catalyst systems should be emphasized, because the amount of nickel species required can be minimized compared with that required for the conventional process.