Akiya Ogawa

Selenium, carbon monoxide and water as a new reduction system: Reductive cleavage of disulfides and diselenides to thiols and selenols

Abstract Disulfides and diselenides were effectively reduced to the corresponding thiols and selenols with carbon monoxide and water using selenium. Disulfides and diselenides were effectively reduced to the corresponding thiols and selenols with carbon monoxide and water using selenium.

Photo-Induced Ditelluration of Acetylenes with Diphenyl Ditelluride

Abstract Diphenyl ditelluride (phTeTePh) adds to a variety of acetylenes upon irradiation with visible light in the absence of solvent to provide vic-bis(phenyltelluro)alkenes in good yields. The reaction may proceed by a radical-chain mechanism that includes the addition to acetylenes of phenyltelluro radical (PhTe e ) generated in situ by photolysis of diphenyl ditelluride, followed by the S H 2 reaction between thus formed β-(phenyltelluro)alkenyl radicals and diphenyl ditelluride. In the cases of unactivated acetylenes such as 1-octyne, the addition proceeds stereoselectively to provide only (E)-vic-bis(phenyltelluro)alkenes. Contrary to this, activated acetylenes like phenylacetylene give rise to a mixture of E- and Z-isomers of vic-bis(phenyltelluro)alkenes. Since the obtained vic-bis(phenyltelluro)alkenes indicate absorption in the near-UV, irradiation with near-UV light in solvent causes a novel reverse reaction of the adducts to the starting acetylenes and diphenyl ditelluride. Accordingly, irradiation with visible light (>400 nm) under high concentrations of the substrates induces the addition of (PhTe) 2 to acetylenes, whereas irradiation with near-ultraviolet (>300 nm) under dilution condition causes the reverse reaction.

The first example of transition-metal-catalyzed hydroselenation of acetylenes

Abstract A variety of transition metal complexes catalyzed the regioselective hydroselenation of acetylenes. In particular, the palladium acetate-catalyzed reaction afforded the Markovnikov adducts with high selectivity.

Photo-initiated addition of diphenyl diselenide to allenes

Abstract Free-radical addition of diphenyl diselenide 2 to allenes 1 took place under irradiation through Pyrex with tungusten lamp to provide 1-(phenylselenomethyl)vinyl selenides 3 in excellent yields.

Cp2TiCl2-Catalyzed pinacol-type coupling of aliphatic aldehydes by use of zinc and chlorosilane

Abstract Bis(cyclopentadienyl)titanium dichloride (Cp 2 TiCl 2 ) exhibits excellent catalytic activity toward the pinacol-type coupling reaction of aliphatic aldehydes with the assistance of zinc powder and chlorosilane.

Highly Selective Three‐Component Coupling of Ethyl Propiolate, Alkenes, and Diphenyl Diselenide under Visible‐Light Irradiation

Just the right strength of carbon-radical trapping by diphenyl diselenide facilitates its selective three-component coupling with an electron-poor alkyne and an electron-rich alkene [Eq. (1)]. In contrast, (PhS)2 is too weak and (PhTe)2 too strong a radical trap, and polymerization of the unsaturated compounds and addition of (PhTe)2 to the alkyne occur, respectively.

Photoinduced reduction of group 16 heteroatom compounds with the aid of samarium diiodide

Abstract A novel photoinduced reduction of group 16 heteroatom compounds such as organic selenides, tosylates, and tellurides has been developed. In particular, organic selenides, which can not be reduced with Sml 2 in the dark (or even in the presence of HMPA), undergo reductive cleavage efficiently by using the Sml 2 -hv system.

Diphenyl diselenide-assisted dithiolation of 1,3-dienes with diphenyl disulfide upon irradiation with near-UV light

While the photoinduced reaction of 1,3-dienes with diphenyl disulfide provides a polymeric mixture, the same reaction in the presence of a catalytic amount of diphenyl diselenide provides the corresponding 1,4-dithiolation products (2) selectively in good yields. The higher carbon radical capturing ability of (PhSe)2 and the reversibility of allylic selenides under photoirradiation contribute to the high efficiency of the conjugate addition of (PhS)2 to 1,3-dienes under radical conditions.

A highly ordered ferrocene system regulated by podand peptide chains

The ferrocene bearing the podand dipeptide chains, Ala-Pro-OEt, which are aligned parallel in solution by the two rigid intramolecular hydrogen bonds, manifests a novel helically ordered arrangement with one turn of 14.70 A pitch height in the crystal packing possibly due to the intramolecular hydrogen bonds (the N–H···OC distance is 2.06 A) and the hydrophobic interaction of the podand dipeptide chains (the distance between the nearest ferrocene units is 4.54 A).

A novel C-H insertion via deoxygenation of amides by a Sm/SmI2 mixed system

Abstract A samarium/samarium diiodide mixed system successfully effects novel aminocyclopropanation and C-H insertion via the deoxygenation of amides. Styrenes undergo aminocyclopropanation by the reaction with aromatic amides, samarium metal, and samarium diiodide. Furthermore, the reaction of aliphatic amides with Sm/SmI2 in the presence of alkylbenzenes like toluene causes benzylic C-II insertion giving the corresponding phenylethylamine derivatives in good yields.