Linear and Nonlinear Optical Properties Of Racemic (±)2-(α-Methylbenzylamino)-5-Nitropyridine Single Crystals

Linear and nonlinear optical properties of racemic (±)2-(α-methylbenzylamino)-5-nitropyridine ((±)MBANP) single crystals have been comprehensively investigated and compared with those of the enantiomorph (–)2-(α-methylbenzylamino)-5-nitropyridine ((–)MBANP) crystals. (±)MBANP crystal exhibits very high chemical and physical stability, but relatively small nonlinear optical coefficients (d₃₁ = 6.8 pm/V, d₃₂ = 4.7 pm/V, d₃₃ = 0.84 pm/V). A comparison between the nonlinear optical coefficients of (±)MBANP and (–)MBANP demonstrates the validity of the oriented-gas model in molecular crystals that neglects all the contributions from intermolecular interaction.     

Numerical reconstruction of an infrared wavefront utilizing an optical phase modulation device

We utilize nitroanisole, that absorbs infrared (IR) radiation as heat, as an optical modulation device based on a thermal process. The nitroanisole exhibits a thermal lens effect, i.e. a temperature dependent refractive index. Hence, the nitroanisole can induce phase modulation to visible light, in direct response to intensity of the incident IR radiation. The proposed method can be used to obtain the phase modulation distribution that corresponds to the IR intensity distribution, i.e. the IR hologram itself, on the nitroanisole by examining the phase map of visible light that is modulated upon passing through the nitroanisole. The IR wavefront can be reconstructed by calculating extracted IR holograms through the Fresnel transform. It is verified that both the amplitude and the phase of the IR wavefront can be reconstructed accurately by proposed method.     

Oxidation of alcohols with oxoperoxobis(N-phenylbenzohydroxamato)molybdenum(VI)

The title complex oxidizes primary and secondary alcohols to the corresponding carbonyl compounds. Stereoselective epoxidation of allylic alcohols is also described.     

Organoaluminium reagents induced isomerization of 5-hydroxy-3,3,6-trimethyl-5-heptenoic acid δ-lactone to 2,2,5,5-tetramethyl-1,3-cyclohexanedione

Treatment of the title lactone and the related δ or ε-lactones with Et₂AlSR (R = Et or Ph) gave 1,3-cyclohexanediones or 1,3-cycloheptanediones in excellent yields.     

Photopolymerization of methyl methacrylate in the presence of tertiary amines

The sensitization effect of tertiary amines on the photopolymerization of methyl methacrylate was studied. N,N-Dimethylbenzylamine, triethylamine, and N,N-dimethylaniline increased the rate of polymerization in this order, but pyridine did not show any effect. A free-radical mechanism was confirmed by the tacticity of polymer, the retarding effect of hydroquinone, and the copolymer composition with styrene. On the basis of the detailed kinetics of the sensitized polymerization and the ultraviolet spectra of the reaction mixtures, a sensitization mechanism is proposed, in which the excited monomer and the amine form a complex and generate an initiating radical.     

Studies directed towards the asymmetric total synthesis of antileukemic lignan lactones. Synthesis of optically pure key intermediate and its utility

By the self-immolative asymmetric synthesis, optically pure key intermediate β-piperonyl-γ-lactone (R)-(+)-$\text{6}$ was found to be prepared in reasonable yield from the easily available chiral γ-lactone synthon ($\text{1}$) which had been also reported to give an antipode (S)-(-)-$\text{6}$. The optically pure (R)-(+)-$\text{6}$ was shown to be converted successfully into several optically pure natural lignan lactones.     

First asymmetric total synthesis of (+)-steganacin determination of absolute stereochemistry

(+)-Steganacin was synthesized in a new and highly specific asymmetric pathway based on the novel application of chiral γ-lactone as a chiral synthon. By this synthesis the absolute stereochemistry of natural (?)-steganacin could be determined in unequivocal way.     

Chiral ligand-controlled asymmetric conjugate addition of lithium amides to enoates

The external chiral ligand-controlled asymmetric conjugate addition reaction of lithium amides with alpha,beta-unsaturated esters provided beta-amino esters in high yields and high enantioselectivities.     

A novel synthesis of 2,3‐dihydro‐1H‐thieno[3,4‐b]pyrroles via ring transformation of cyclic sulfonium ylides by titanium(IV) chloride‐triethylamine system

A series of cyclic sulfonium ylides 4a‐h reacted with titanium( IV ) chloride in the presence of triethyl‐amine to give the corresponding fused 2,3‐dihydro‐1H‐thieno[3,4‐b]pyrroles 5a‐h , via a ring opening and recyclization. In contrast, treatment of compounds 4a, 4b, 4e and 4f with titanium(IV) chloride, triethy‐lamine and dimethylamine hydrochloride gave the corresponding thiophenes 6a, 6b, 6e and 6f . Furthermore, compounds 6a and 6b easily underwent cyclization with sodium hydride to afford the corresponding 5a and 5b .