Photochemische Reaktionen. 39. Mitteilung. Photochemische Umwandlungen von endo-Tricyclo[4.3.12,5.0]-decadien-(3,8)-dion-(7,10) und cis-8, 9-Dihydroindenon

In boiling xylene the cyclopentadienedione 1 is thermally decarbonylated to cis-8,9-dihydroindenone ( 8 ). This method avoids secondary reactions and allows the preparation of 8 in high yield.     

Bildung tricyclischer Thietan-Derivate durch intramolekulare(2+2)-Cycloaddition

Formation of Thietane Derivatives via Intramolecular (2+2) Cycloaddition On irradiation, the two 4-vinyl-1,3-thiazole-5(4H)-thiones 1a, b , synthesized from thiobenzoic acid and the corresponding 3-amino-2H-azirines 2a , b , undergo an intramolecular (2+2)-cycloaddition reaction of the C?S and C?C bonds to give the tricyclic thietane derivatives 3a , b .     

Gleichgewichts-(cis-1,4-1,2)Polybutadien

Ohne Zusammenfassung     

Irreversible Isomerisierung von halogenfunktionellen Tris(silyl)hydroxylaminen durch dyotrope Umlagerung

Irreversible Isomerization of Halofunctional Tris(silyl)hydroxylamines by Dyotropic Rearrangement In the reaction of halosilanes with lithiated N,O-bis(trimethylsilyl)hydroxylamine the substitution occurs at the oxygen atom. Depending on the substituents a dyotrope rearrangement leads to the isomeric N-halosilyl-N,O-bis(trimethylsilyl)hydroxylamines: PhSiF₂N(SiMe₃)OSiMe₃ 1 , PhCH₂SiF₂N(SiMe₃)OSiMe₃ 2 , Cl₃SiN(SiMe₃)OSiMe₃ 3 at higher temperature.     

Steric effects in the electroreduction of 9-anthryl styryl ketone and 9,10-anthryl bis(styryl ketone)

The electrochemical behavior of 9-anthryl styryl ketone (ASK) and 9,10-anthryl bis(styryl ketone) (ABSK) in acetonitrile and N,N-dimethylformamide at a Pt electrode was investigated by cyclic and rotating ring disk electrode (RRDE) voltammetry and controlled potential coulometry. ASK is reduced in a reversible one-electron step to form the radical anion which rapidly couples (k₂=10⁵M^?1 s^?1) to form the dimeric dianion. The dimer can be reoxidized to form ASK. ABSK is reversibly reduced to the stable dianion which shows no tendency to couple. The cyclic voltammogram wave shape suggests that the styryl-keto groups in the 9-and 10-positions are non-interacting so that the reduction occurs in two steps whose standard potentials differ by the statistically predicted 36 mV.     

1,2-二(对-甲苯基)-1,2-二甲基二硅桥连二环戊二烯基四羰基二铁的合成及热重排反应

Cl2MeSiSiMeCl2与环戊二烯基锂及对甲苯基溴化镁反应, 生成C5H5(p-Tol)MeSiSiMe(p-Tol)C5H5. 后者再与五羰基铁反应, 得到标题化合物[η5, η5-C5H4(p-Tol)MeSiSiMe(p-Tol)C5H4]Fe2(CO)2(μ-CO)2(3); 同时还得到两个单硅桥连副产物[η5, η5-(p-Tol)2MeSiSiMe(C5H4)2]Fe2(CO)2(μ-CO)2(4)和[η5, η5-(p-Tol)Me2SiSiMe(C5H4)2]Fe2(CO)2(μ-CO)2(5). 化合物3中顺式异构体(3a)占绝对优势, 可通过简单重结晶分离出纯品. 化合物3a在加热条件下发生分子内的硅硅键和铁铁键之间的复分解重排反应, 生成[η5-(p-Tol)MeSiC5H4Fe(CO)2]2(6). 该产物为顺反异构体的混合物(顺反异构体的摩尔比为4:3), 表明重排反应不涉及协同历程. 利用X射线衍射法测定了化合物4的分子结构.     

The Syntheses and Crystal Structures of cis-[Bis(diphenylphosphino)methane][1,2-bis(diphenylphosphlno)ethane] dicarbonylmolybdenum(O) and cis-[1,2-Bis(diphenylphosphino)ethane] [cis-1,2-bis(diphenylphosphino) ethylene]dicarbonylmolybdenum(0)

The title compounds, Mo(CO)₂(Ph₂PCH₂PPh₂)(Ph₂PCH₂CH₂PPh₂), Mo(CO)₂(dppm)(dppe) 1, and Mo(CO)₂(Ph₂PCH₂CH₂PPh₂)(Ph₂PCH = CHPPh₂), Mo(CO)₂(dppe)(cis-vpp) 2, were prepared from Mo(CO)₆ and the corresponding bidentate diphosphine ligands in n-decane under nitrogen atomosphere. Crystals of 1 are monoclinic, space group P 2₁/c, with a = 19.072(3), b = 11.348(3), c = 23.57(1) Å, β = 99.64(3)°, Z = 4, and the final residual R(F) = 0.044 for 4810 observed reflections; data of 2 are triclinic, space group P 1, with a = 12.091(3), b = 12.186(8), c = 18.934(5) Å, α = 96.93(4),β = 108.15(2), γ = 107.08(4)deg;, Z = 2, and the final residual R(F) = 0.058 for 4570 observed reflections. The distortion of compound 1 is more pronounced than that of compound 2, The two Mo-P lengths in the same bidentate chelate ligand for both compounds are different. Among them, the two larger Mo-P bond lengths for compound 2 are similar, but significantly different for 1.     

Photochemistry of the anthracene chromophore: Synthesis and photochemical isomerization of 1,2-di(9-anthryl)-1-hydroxypropene,a novel simple enol

Enolization and subsequent methylation of 1,2-di(9-anthryl)ethanone leads to photolabile E/Z-isomeric α,β-substituted dianthrylethylenes. 1,2-Di(9-anthryl)propanone forms a crystalline enol which isomerizes photochemically in solution by a unique H shift.     

Thermal chemistry of cis-1,2-dichloroethene on Pd(111)

The reaction of cis-1,2-dichloroethene (cis-DCE) on Pd(111) has been investigated by temperature-programmed desorption, laser-induced thermal desorption, Auger electron spectroscopy, and Fourier transform reflection absorption infrared spectroscopy. Below 130 K, molecularcis-DCE aggregates, resulting in only about 30% of the molecules from exposures below saturation significantly interacting with the palladium surface. The decomposition of cis-DCE generates the observable species H2, HCl, and ethylidyne. A fraction of cis-DCE molecules lose both chlorine atoms and add hydrogen to form ethylidyne, which is stable on the surface between 250 and 370 K. Hydrogen is liberated at about 420 K from cis-DCE surface fragments that immediately combine with surface chlorine and desorb as HCl. The most intense HCl desorption occurs at about 575 K and is due to surface chlorine reacting with either subsurface hydrogen or hydrogen from the remaining surface alkyl fragments. No carbon-containing species desorb from the decomposition of cis-DCE.     

Solvent-dependent effect by carbon dioxide on the photoreactions of (9-anthryl)alkylamines

The effect of CO₂ on a photoreaction was first studied systematically by using (9-anthryl)alkylamines (APA, AEA, and AMA) as the starting compound. From close scrutiny of the results, the CO₂ effect was clearly observed and was well rationalized by the previously reported novel solvent dependence of the amine-CO₂ reversible reactions. For instance, the yield of the dimer (h-t from APA or AEA, h-t+h-h from AMA) obtained in MeOH or DMSO was higher under CO₂ than under argon and this was ascribed to formation of either ammonium bicarbonate/carbonate in MeOH or carbamic acid in DMSO, which will prevent the nitrogen lone pair from being involved in electron-transfer reactions. In fact, the electron-transfer side reactions producing 1-3 in DMSO were strongly inhibited under CO₂. Also, due to formation of noncovalent linkage between the ammonium cation and the carbamate anion in 2-PrOH, the proportion of h-h relative to h-t produced from AMA in 2-PrOH was increased by carrying out the reaction under CO₂.