Double elimination protocol for synthesis of 5,6,11,12-tetradehydrodibenzo[a,e]cyclooctene

A new method for constructing 5,6,11,12-tetradehydrodibenzo[a,e]cyclooctene is described on the basis of one-pot double elimination protocol. The target molecule, which is the smallest cyclophane with alternate arylene-ethynylene linkage, is synthesized in 61 % yield through oxidative dimerization of ortho-(phenylsulfonylmethyl)benzaldehyde. The initial carbon-carbon bond formation between sp(3) carbons followed by stepwise conversion to sp(2) and finally sp carbons bypasses the difficulty encountered in direct coupling of the sp carbon in the terminal acetylene. The mechanism of this process is discussed. The Wittig-Horner-type coupling is a key reaction employed for the carbon-carbon bond formation. Generation of (E)-vinylsulfone moiety in the first coupling between alpha-sulfonyl anion and aldehyde functions is crucial for the effective second coupling to complete the cyclization. The syn-elimination of the (E)-vinylsulfone moieties in the cyclized intermediate furnishes the acetylenic bonds.     

Two-Step Synthesis,Structure, and Optical Features of a Double Hetero[7]helicene

A novel double aza-oxa[7]helicene was synthesized from the commercially available N¹,N⁴-di(naphthalen-2-yl)benzene-1,4-diamine and p-benzoquinone in two steps. Combining the acid-mediated annulation with the electrochemical sequential reaction (oxidative coupling and dehydrative cyclization) afforded this double hetero[7]helicene. Moreover, the structural and optical features of this molecule have been studied using X-ray crystallographic analysis, and the absorption and emission behaviors were rationalized based on DFT calculations.     

Double diastereoselective [3,3]-sigmatropic aza-Claisen rearrangements

Asymmetric [3,3]-sigmatropic aza-Claisen rearrangement of the (Z)-N-allyl-N,O-silylketene aminal of (3S,4E,alphaR)-1-benzyloxy-3-(N-propionyl-N-alpha-methylbenzylamino)hex-4-ene furnishes (2S,3R,4E,alphaR)-N-alpha-methylbenzyl-2,3-dimethyl-7-benzyloxyhept-4-enamide in > 92% d.e.; rearrangement of the diastereomeric (3R,4E,alphaR)-(Z)-N,O-silylketene aminal proceeds with low diastereoselectivity.     

Electrosynthesis of Dihydropyrano[4,3-b]indoles Based on a Double Oxidative [3+3] Cycloaddition

Oxidative [3+3] cycloadditions offer an efficient route for six-membered-ring formation. This approach has been realized based on an electrochemical oxidative coupling of indoles/enamines with active methylene compounds followed by tandem 6π-electrocyclization leading to the synthesis of dihydropyrano[4,3-b]indoles and 2,3-dihydrofurans. The radical–radical cross-coupling of the radical species generated by anodic oxidation combined with the cathodic generation of the base from O₂ allows for mild reaction conditions for the synthesis of structurally complex heterocycles.     

Preparation and Characterization of a New Lamellar Double Hydroxide [CdCrCl]

The lamellar double hydroxide, abbreviated notation [CdCrCl], was prepared by reacting solid CdO with a solution of CrCl3,6H₂0, then characterized by X-ray powder diffraction and IR spectroscopy. This new compound crystallizes in the hexagonal system with two layers in each elementary cell (2H polytype). The structure is described by the space group P6₃/mmc. Cell parameter values are a=3.33 ≈ and c = 15.71 ≈. The exchange properties of the material have been studied with the anions N0₃⁻, C0₃²⁻ and S0₄²⁻     

Theoretical study of the electronic structure of HXY/XYH radicals (X[Double Bond]C,Si;Y[Double Bond]O,S)

The electronic structures of the HXY/XYH compounds (X[Double Bond]C,Si;Y[Double Bond]O,S) on the (2)A(') electronic ground state were investigated by applying the natural bond orbital (NBO) method to the computed B3LYP6-311G(**) wave functions. Different localized structures are proposed for the HXY and XYH isomers and the central XY unit is described as intermediate between a double and a triple bond in HCO, HCS, HSiO, and HSiS, similar to a double bond in COH, CSH, and SiSH, and clearly a single bond in SiOH. Through the comparison between the NBO results for the diatomic and hydrogenated compounds, the energy preferences on each pair of isomers and the computed geometrical parameters are explained. According to the structures proposed, the HXY compounds are sigma radicals with the spin density distributed along the molecular framework, while the XYH compounds are pi radicals with most of the unpaired spin located on an almost pure p orbital of the X atom. Finally, the amounts of spin density on natural atomic orbitals provided by the NBO method are used to explain the computed values of the isotropic and anisotropic hyperfine coupling constants.     

Polycyclic arene sulfides. Preparation of 1a,2,3,11b-tetrahydrobenz-[5,6]anthra[1,2-b]thiirene, 6b,7a,8,9-tetrahydrobenzo[10,11]-chryseno[1,2-b]thiirene,and 7,8,8a,9a-tetrahydrobenzo-[10,11]chryseno[3,4-b]thiirene

The title compounds 5, 7 and 9 which are the first arene sulfides of 7,8-dihydrobenz[a]anthracene, 8,9-and 10,11-dihydrobenzo[a]pyrene, respectively, have been synthesized by treatment of the corresponding arene oxides 4, 6 and 8 with N,N-dimethylthioformamide in the presence of catalytic amounts of trifluoroacetic acid.     

Electrosynthesis of Dihydropyrano[4,3‐b]indoles Based on a Double Oxidative [3+3] Cycloaddition

Oxidative [3+3] cycloadditions offer an efficient route for six‐membered‐ring formation. This approach has been realized based on an electrochemical oxidative coupling of indoles/enamines with active methylene compounds followed by tandem 6π‐electrocyclization leading to the synthesis of dihydropyrano[4,3‐b]indoles and 2,3‐dihydrofurans. The radical–radical cross‐coupling of the radical species generated by anodic oxidation combined with the cathodic generation of the base from O₂ allows for mild reaction conditions for the synthesis of structurally complex heterocycles.     

Double proton-proton resonance of substituted polychlorbicyclo[2.2.1]heptenes

Conclusion The given analysis of the four spin AABB system shows that the use of the INDOR technique substantially simplifies the problem of analyzing spectra as compared with the methods of identification which have been previously used [14, 16], which, although they lead to the desired result, make excessive demands on machine time and require running a number of trial assignments. It should be noted that INDOR does possess the disavantage of a loss of sensitivity as compared with conventional spectra which imposes some restriction on its use in the analysis of spectra of difficultly soluble compounds.Institute of Chemical Physics, Academy of Sciences of the USSR. Institute of Natural Product Chemistry, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 12, No. 2, pp. 224–230, March–April, 1971     

Dihydrodiols and diol epoxides of dibenzo[a,i]-and [a,h]pyrene

Syntheses of dihydrodiols and highly mutagenic diol epoxides of the carcinogenic polycyclic aromatic hydrocarbons dibenzo[a,i]-and [a,h]pyrene are described.