Deprotection of dithioacetals with 30% hydrogen peroxide catalyzed by tantalum(V) chloride–sodium iodide or niobium(V) chloride–sodium iodide

The reaction of dithioacetals with 30% hydrogen peroxide in the presence of catalytic amounts of tantalum(V) and iodide ion effectively produced carbonyl compounds in high yields. Dithioacetals also can be deprotected using the niobium(V) catalyzed oxidation of iodide ion by hydrogen peroxide under mild conditions.     

Non-destructive elemental analysis of large meteorite samples by prompt gamma-ray neutron activation analysis with the internal mono-standard method

Prompt gamma-ray neutron activation analysis (PGNAA) using the internal mono-standard method was tested for its applicability to analyzing large solid samples including irregularly shaped meteorite samples. For evaluating the accuracy and precision of the method, large quantities of the Geological Survey of Japan standardized rock powders (JB-1a, JG-1a, and JP-1) were analyzed and 12 elements (B, Na, Mg, Al, Cl, K, Ca, Ti, Mn, Fe, Sm, and Gd) were determined by using Si as an internal standard element. Analytical results were mostly in agreement with literature values within 10 %. The precision of the method was also shown to be within 10 % (1σ) for most of these elements. The analytical procedure was then applied to four stony meteorites (Allende, Kimble County, Leedey, Lake Labyrinth) and four iron meteorites (Canyon Diablo, Toluca (Mexico), Toluca (Xiquipilco), Squaw Creek) consisting of large chunks or single slabs. For stony meteorites, major elements (Mg, Al, Si, S, Ca, and Ni), minor elements (Na and Mn) and trace element (B, Cl, K, Ti, Co, and Sm) were determined with adequate accuracy. For iron meteorites, results for the Co and Ni mass fractions determined are all consistent with corresponding literature values. After the analysis, it was confirmed that the residual radioactivity remaining in the sample after PGNAA was very low and decreased down to the background level. This study shows that PGNAA with the internal mono-standard method is highly practical for determining the elemental composition of large, irregularly shaped solid samples including meteorites.     

Intramolecular 1,3‐Dipolar Cycloaddition‐Mediated Stereoselective Synthesis of Disubstituted Cyclopentane: A Simple Model for the Cyclopentane Ring System of Polycyclic Oroidine Alkaloids

We present a diastereoselective synthesis of disubstituted cyclopentane 8 having a nitrogen‐containing quaternary carbon center, which is found in axinellamine A ( 5 ) and related compounds. During this work, we found that the 1,3‐dipolar cycloaddition product 24 immediately underwent intramolecular redox reaction at the newly formed morpholin‐2‐one moiety, thus affording disubstituted cyclopentane containing a tertiary amine ( 9 ) stereoselectively in good yield. The amine 9 was successfully converted into guanidine 31 , which corresponds to 8 , through iminium cation–enamine isomerization.     

Sesquifulvalene Trapping as a [12+2] Adduct with Tetracyanoethylene

Sesquifulvalene (1) is a substance of considerable theoretical interest¹ which is expected to have a significant contribution to its structure from the dipolar resonance form 1b,² and hence an exceptionally low bond order for the central double bond. Although a wide variety of annelated and otherwise substituted sesquifulvalenes have been prepared and characterized,³ the parent substance has proved remarkably elusive. Very recently, a preparation of 1 in crystalline form has been reported, based upon elimination of an acetoxy-11,12-dihydrosesquifulvalene derivative.⁴     

Synthesis and Metal Complex Formation of a Bis(terpyridine) Derivative with a Phenylacetylene Framework

A new bis(terpyridine) derivative with a phenylacetylene framework was synthesized via a stepwise terpyridine construction strategy. The addition of ZnCl₂ to a solution of the bis(terpyridine) in chloroform resulted in UV/vis and ¹H NMR spectral changes because of complex formation.     

Synthesis of 2,3-dihydro-1H-isoindole-1-thiones via the bromine–lithium exchange between 1-bromo-2-(1-isothiocyanatoalkyl)benzenes and butyllithium

The reaction of 1-bromo-2-(1-isothiocyanatoalkyl)benzenes, which are easily derived from 2-bromophenyl ketones or (2-bromophenyl)methanamine, with butyllithium generates 1-(1-isothiocyanatoalkyl)-2-lithiobenzenes, which immediately underwent intramolecular cyclization to give rise to the corresponding 3-substituted and 3,3-disubstituted 2,3-dihydro-1H-isoindole-1-thiones in good yields.     

Comprehensive characterisation of the E phase of 6-octyl-2-phenylazulene

Molecular dynamics in the soft crystal, E phase of 6-octyl-2-phenylazulene was studied by X-ray diffraction, and dielectric and Fourier transform infrared spectroscopies. Clear dielectric dispersion is observed due to the head-to-tail disordering in a kHz range around 400 K. The CH stretching frequencies exhibit more pronounced shifts at the phase transition point from the high-temperature ordered crystal to the E phase than that at the melting from the E phase to the isotropic liquid. The results are discussed in comparison with a typical E series, 4-n-alkyl-4′-isothiocyanatobiphenyl (n being the number of carbon atoms in the alkyl group).     

Controlling the photochemical reactions of alkenes by light-path length effects of a microchannel reactor

Photoirradiation of Me₂CO–H₂O solution of pent-4-en-1-ol (1a) with a high-pressure mercury lamp in a test tube gave 8-hydroxyoctan-2-one (3a) in 66 % yield along with oxetane (4a) and the isomer (4a′) in 10 % yield. Irradiation of the running Me₂CO–H₂O solution of 1a in the flow system of a microchannel reactor (MCR) gave mainly 4a. The photoreaction of 1,1-diphenylethene (2a) with triethylamine gave a Markovnikov-type adduct (5a) and an anti-Markovnikov-type adduct (6a). The use of the MCR enhanced the production of 5a. These phenomena were explained by the light-path length effects of the MCR.     

Ni‐Catalyzed [4+3+2] Cycloaddition of Ethyl Cyclopropylideneacetate and Dienynes: Scope and Mechanistic Insights

A detailed study of the Ni‐catalyzed [4+3+2] cycloaddition reaction between ethyl cyclopropylideneacetate and dienynes has been conducted, resulting in the development of a new method for the synthesis of compounds containing nine‐membered rings. We studied the reactivity of various dienynes, together with their substituent and conformational effects. The mechanism of the reaction was probed by examining the stoichiometric reactions of the Ni complexes and dienynes.