Dimeric Tetrathiafulvalene Linked to pseudo‐ortho‐[2.2]Paracyclophane: Chiral Electrochromic Properties and Use as a Chiral Dopant

A dimeric tetrathiafulvalene installed into a chiral pseudo‐ortho‐[2.2]paracyclophane framework was synthesized as a novel chiral electrochromic material. This compound exhibited pronounced chiroptical properties in the UV‐Vis‐NIR range depending on its redox states without racemization. Each enantiomer was examined as a chiral dopant for nematic liquid crystals (LCs), and the induced helicity of the LC solvent was in accord with that of the tetrathiafulvalene compound.     

Rhodium-catalyzed anti selective cross-addition of bis(trimethylsilyl)acetylene to diarylacetylenes via carbon-silicon bond cleavage

The addition of bis(trimethylsilyl)acetylene to diarylacetylenes proceeds efficiently and selectively in a formal anti fashion in the presence of [Rh(OH)(cod)]2/bisphosphine and phenol as catalyst and activator, respectively, accompanied by cleavage of one of the C-Si bonds to produce the corresponding (Z)-enynes. The products can further couple with the same or a different diarylacetylene molecule to give rise to (Z,Z)-1,2,5,6-tetraaryl-1,5-hexadien-3-ynes that show relatively strong solid-state fluorescence.     

Direct lactone formation by using hypervalent iodine(III) reagents with KBr via selective C-H abstraction protocol

We have developed a new and reliable method for the direct construction of biologically important aryl lactones and phthalides from carboxylic and benzoic acids, using a combination of hypervalent iodine(III) reagents with KBr.     

Remarkable effect of N-substituent on enantioselective ruthenium-catalyzed propargylation of indoles with propargylic alcohols

Ruthenium-catalyzed enantioselective propargylation of indoles with propargylic alcohols affords the corresponding beta-propargylated indoles in good yields with a high enantioselectivity (up to 95% ee). A remarkable effect of the nature of the N-substituent of indoles is observed for the enantioselectivity of the propargylated indoles. The preparative method described in this paper may provide a novel protocol for asymmetric Friedel-Crafts alkylation of indoles using propargylic alcohols as a new type of electrophiles.     

Silicon-carbon unsaturated compounds. 77. Thermal behavior of cis- and trans-1-silacyclobut-3-ene formed from pivaloyl[tert-butylbis(trimethylsilyl)]silane and tert-butylacetylene

The reaction of tert-butylbis(trimethylsilyl)silyl potassium with pivaloyl chloride gave pivaloyl[tert-butylbis(trimethylsilyl)]silane (1) in 89% yield. The cothermolysis of 1 with tert-butylacetylene at 140 °C for 24 h produced the mixture consisting of cis- and trans-1,2,3-tri(tert-butyl)-2-(trimethylsiloxy)-1-(trimethylsilyl)-1-silacyclobut-3-ene (cis-2 and trans-2) in a ratio of 0.7: 1, in 88% combined yield. The thermolysis of the mixture, cis-2 and trans-2, at 250 °C for 24 h proceeded to give trans-1,2,4-tri(tert-butyl)-1-(trimethylsiloxy)-2-(trimethylsilyl)-1-silacyclobut-3-ene (4) as a single product in 96% yield. Similar treatment of cis- and trans-2 at 190 °C for 15 h afforded silylcyclopropene 3 quantitatively, which underwent further isomerization at 250 °C to give trans-1-silacyclobut-3-ene 4 in quantitative yield.     

Crystal structure of 1,10-dibromodecane and its infrared intensity in a urea clathrate and in the crystal

The crystal structure of 1,10-dibromodecane belongs to the monoclinic system and the space group is P2(1)/c with lattice dimensions of a = 5.4574(3) A, b = 5.2814(4) A, c = 21.088(1) A and beta = 92.897(2) degrees and zeta = 2. Infrared spectra of 1,10-dibromodecane in a urea clathrate and in the crystal were observed to investigate the effect of molecular interaction on infrared intensity. The infrared intensity of the CH(2) waggings in the crystalline state is 1.5-1.9 times stronger on the relative basis than that in a urea clathrate, whereas those of CH(2) stretching, CH(2) rocking and CH(2) bending are almost the same in both states. The former enhancement is explained in terms of increase in the bond moment of the C(alpha)H(2) group on the basis of crystal structure and the electrostatic model. The relative intensity of two CH(2) asymmetric stretching changes between the two states. This is also analyzed by the use of the electrostatic model.     

Strong Time Operators Associated with Generalized Hamiltonians

Let the pair of operators, (H, T), satisfy the weak Weyl relation: $$T{\rm e}^{-itH}={\rm e}^{-itH}(T+t),$$ where H is self-adjoint and T is closed symmetric. Suppose that g is a real-valued Lebesgue measurable function on ${\mathbb {R}}$ such that ${g\in C^2(\mathbb {R}\backslash K)}$ for some closed subset ${K\subset\mathbb {R}}$ with Lebesgue measure zero. Then we can construct a closed symmetric operator D such that (g(H), D) also obeys the weak Weyl relation.