Synthesis and characterization of tetraoctyloxy substituted naphthalenophanedienes

Tetraoctyloxy-substituted naphthalenophanedienes were synthesized from tetraoctyloxy-substituted dithia[3.3]naphthalenophanes via sequential benzyne Stevens rearrangement, oxidation, and pyrolysis reactions. Surprisingly, only the pseudo-geminal isomer of tetraoctyloxy-substituted dithia[3.3]naphthalenophane was obtained after cyclization of the corresponding starting materials. The structures of the pseudo-geminal isomers of tetraoctyloxy-substituted dithia[3.3]naphthalenophane and tetraoctyloxy-substituted naphthalenophanediene were fully determined by nuclear magnetic resonance spectroscopy, high resolution mass spectrometry, and X-ray crystallography. The pseudo-geminal and pseudo-meta diastereomers of tetraoctyloxy-substituted naphthalenophanedienes were isolated by multiple fractional recrystallization from hexane at 5 °C. The solid state structure of the pseudo-geminal isomer of tetraoctyloxy-substituted naphthalenophanediene revealed strongly distorted naphthyl rings with high levels of ring strain.     

A useful ring transformation route to novel thiazepino[7,6-b]indoles from monochloro-β-lactam-fused 1,3-thiazino[6,5-b]indoles,analogues of cyclobrassinin

The Staudinger ketene-imine cycloaddition reactions of cyclobrassinin phytoalexin analogues 2-aryl-4,9-dihydro-1,3-thiazino[6,5-b]indoles with chloroacetyl chloride as a ketene source were investigated under different conditions. Both β-lactam ring formation and the N-chloroacetylation of the indole moiety took place. The indole N-chloroacetyl group can be easily removed by treatment in the presence of silica gel in methanol at reflux temperature. The selective β-lactam formation can be also achieved in certain cases under milder Staudinger conditions. The treatment of azeto[2,1-b]thiazino[6,5-b]indole-1-one derivatives with sodium ethoxide in ethanol provided the novel thiazepino[7,6-b]indole ring systems in a one-step ring transformation. The structures of the new ring systems were determined by means of IR and NMR spectroscopy.     

Synthesis and ring opening reactions of 2-glyco-1,4-dimethyl-3-nitro-7-oxabicyclo[2.2.1]hept-5-enes

The high-pressure asymmetric Diels-Alder reactions of d-galacto- (1a) and d-manno-3,4,5,6,7-penta-O-acetyl-1,2-dideoxy-1-nitrohept-1-enitol (1b) with 2,5-dimethylfuran (2) afforded mixtures of cycloadducts, from which the (2S,3R)-3-exo-nitro (3a and 3b), (2R,3S)-3-exo-nitro (4a and 4b), and (2R,3S)-1′,2′,3′,4′,5′-penta-O-acetyl-1′-C-(1,4-dimethyl-3-endo-nitro-7-oxabicyclo[2.2.1]hept-5-en-2-exo-yl)-d-galacto-pentitol (5b) were isolated pure. Deacetylation of these compounds led to new chiral mono-, bi-, and tricyclic ethers, being their asymmetric centers arising from the chiral inductor used in the cycloaddition reaction. A ring opening mechanism through a 1-nitro-1,3-cyclohexadiene intermediate has been proposed.     

Synthesis of the western half of breviones C, D, F and G

The enantioselective synthesis of the diterpenic moiety in the abeo-breviano skeleton is reported. The synthesis is carried out starting from 2-methyl-1,3-cyclohexanedione and EVK in eleven steps following a ring-expansion strategy once the tricyclic perhydrophenantrene skeleton has been obtained. A new Tiffeneau-Demjanov rearrangement under dark conditions is reported in which the insertion of the new methylene group is directed towards the most hindered side of the carbonyl group. This result is new and opposite to those reported in the literature under light (filtered or un-filtered wavelengths) conditions where insertion in the less hindered side is usually preferred.     

Stereoselective Total Synthesis of Dodoneine

A simple and highly efficient stereoselective total synthesis of dodoneine ( 1 ), a naturally occurring bioactive 5,6‐dihydro‐2H‐pyran‐2‐one, was achieved. The synthesis involved Keck's asymmetric allylation, iodine‐induced electrophilic cyclization, and Grubbs' catalyzed ring‐closing metathesis as key steps.     

Methyl 3-bromomethyl-3-butenoate as an isopentane building block for the stereoselective preparation of (S)-4-methyl-3,6-dihydro-2H-pyran-2-carbaldehyde and (+)-faranal

(S)-4-Methyl-3,6-dihydro-2H-pyran-2-carbaldehyde (3), the common intermediate in the syntheses of the C17-C27 subunit of laulimalide (4) and (+)-faranal (5), the trail pheromone of the pharaoh ant, Monomorium pharaonis, were obtained via transformation of methyl 3-bromomethyl-3-butenoate (1) into allylstannane 2 and subsequent allylation of (benzyloxy)acetaldehyde (6) in accordance with the Keck procedure as the key steps.     

Detection and analysis of new bands of O3 by CRDS between 6500 and 7300 cm

The absorption spectrum of the ¹⁶O₃ isotopologue of ozone has been recorded in the 7000-7920 cm⁻¹ region by high sensitivity CW-Cavity Ring Down Spectroscopy. This report is devoted to the analyses of the 7065-7300 cm⁻¹ region dominated by the ν₁ + 2ν₂ + 5ν₃ and ν₁ + 5ν₂ + 3ν₃ A-type bands at 7130.8 and 7286.8 cm⁻¹ respectively. 289 transitions were assigned to the ν₁ + 2ν₂ + 5ν₃ band. The corresponding line positions were modeled with an effective Hamiltonian involving Coriolis resonance interactions between the (1 2 5) upper state and the (4 4 0), (0 2 6) and (6 1 0) dark states, and an anharmonic resonance interaction with the (2 0 5) state. The very strong interaction (up to 50% mixing of the wavefunctions) between the (1 2 5) and (6 1 0) states leads to the observation of two extra lines of the 6ν₁ + ν₂ band due to a resonance intensity transfer. 213 transitions of the ν₁ + 5ν₂ + 3ν₃ band were assigned and modeled taking into account a Coriolis resonance interaction with the (3 6 0) state.We take the opportunity of the present work to report the analysis of the very weak 4ν₂ + 4ν₃ B-type band at 6506.1 cm⁻¹ which was assigned from previously recorded CRDS spectra. 286 transitions were modeled using the effective Hamiltonian approach.The dipole transition moment parameters of the three analyzed bands were determined by a least-squares fit to the measured line intensities. For the three studied band systems, the effective Hamiltonian and transition moment operator parameters were used to generate line lists provided as Supplementary Materials.     

Photophysical property of rhodamine-cored poly(amidoamine) dendrimers: Simultaneous effect of spirolactam ring-opening and PET process on sensing trivalent chromium ion

Two novel poly(amidoamine) (PAMAM) dendrimers, comprising rhodamine B unit in the core and 1-phenyl-3-methyl-5-pyrazolone unit at the periphery, have been synthesized and characterized. Both dendrimers displayed high selectivity and sensitivity towards Cr³⁺ ion. As considering the potential of being applied as fluorescent sensors for Cr³⁺ ion, we studied the complexes formed between the dendrimers and Cr³⁺ ion. Different PAMAM dendrimers had different recognition mechanism towards Cr³⁺ ion. For dendrimer G2, the recognition of Cr³⁺ was mainly due to the ring-opening of spirolactam. However, it significantly depended on the simultaneous effect of ring-opening of spirolactam and photoinduced electron transfer (PET) in the case of dendrimer G3.     

Photonic crystal based cross connect filters

We propose optical cross connect filters using photonic crystal ring resonators coupled waveguide crossings. We investigate the properties of this component numerically by using the finite-difference time-domain method. Our simulations reveal that the photonic crystal based cross connect filter has more than 92% normalized transmission. Extending our concept for cross connection applications, we demonstrate a 1 × 2 PC-based cross connect filter which utilizes a heterostructure. In this filter, at the resonance of each ring resonator, the normalized power transferred to the related waveguide of the two drop waveguides is found to be more than 91%.     

Numerical analysis of the output power of the injection-locked cw Ti:sapphire lasers

The optimization analysis of the output power of the injection-locked cw Ti:sapphire lasers is presented based on the fact that the injection-locked and free-running lasers almost have the same maximum output power. With the modified Ti:sapphire laser model, the dependences of the threshold and slope efficiency on the ring cavity and crystal parameters are studied through the numerical calculations, which clarify the roles of various parameters in affecting the output power. Our calculated results are in good agreement with the reported experimental data for the laser at 756 nm. Therefore our numerically calculated results could be used as a guideline for designing and optimizing such kind of the lasers.