Search

A low-cost type terahertz time-domain spectroscopic system can be constituted using a multimode laser diode instead of a pulse laser. To suppress noise, a window function is usually used in the Fourier transformation. When this system is used to measure an optically thick sample, the obtained refractive index shows sinusoidal structures. This is caused by ingress of a signal fragment into the measured range and egress of another signal fragment out of the measured range. In addition, a broad positive background component appears in the imaginary part of the refractive index. This is because of the decreased amplitude of the central structure of the signal, which results from the time shift under the window function caused by sample insertion. These false structures can be eliminated by using a modified window function that is shifted with the signal when the sample is inserted.

A sub-terahertz time-domain spectroscopic system with spiral antennas, which have high efficiency in the sub-THz region, was applied to imaging. In the time-domain signals, there were several peaks with various widths. Images were obtained by translating samples at the focus of the sub-THz beam with the time delay fixed at certain positions while monitoring the signal. At the edge of the metal patterns, the signal basically showed step-like variations, which were sometimes accompanied by overshoot structures (peaks and dips) depending on the time-delay position. The overshoot can be utilized to make the images sharper. The time-delay position can be adjusted to make the step height zero and produce images that contain only the overshoot, which can be transformed into images of the edge lines of the metal pattern. In addition, an image of the watermark on a 1000-yen bill was obtained. The image contrast caused by the small variation of the bill paper thickness was enhanced by locating the time delay at the position where the signal shows maximum sensitivity to the phase shift.

We demonstrate that the carrier density, scattering time, and wafer thickness of a doped Si wafer can be determined independently by measurement using a sub-THz spectroscopic system with an inexpensive continuous-wave multimode laser diode instead of a femtosecond laser. Because the THz signal spectrum of this system is almost discrete, we propose an improved algorithm for extracting these parameters from experimental data. We also demonstrate the two-dimensional imaging of the carrier-density distribution in the Si wafer.

A new and convenient method for the preparation of 3-substituted benzo[b]thiophenes was developed. a-Substituted 2-(1-phenylethylthio)styrenes, which could easily be prepared from 2-mercaptophenyl ketones or benzenethiols in two or three steps, respectively, underwent 5-endocyclization on treatment with iodine in the presence of sodium hydrogencarbonate in acetonitrile at room temperature to give 3-substituted benzo[b]thiophenes in fair to good yields.

Efficient methods have been developed for the preparation of 1(3H)-imino-2-benzothiophene and 1-imino-1H-2-benzothiopyran derivatives. Treatment of secondary o-(vinyl)thiobenzamide derivatives with iodine in the presence of sodium hydrogencarbonate in acetonitrile at 0 °C gave the former derivatives. Similar treatment at reflux gave the latter derivatives.

A convenient synthetic method for 1-aryl-1H-indole derivatives has been developed. 2-(Arylamino)-α-methylstyrene derivatives were treated with iodine in the presence of sodium hydrogencarbonate to give 1-aryl-3-methyl-1H-indole derivatives in fair to good yields. 3-Ethyl-2-methyl-1-phenyl-1H-indole and 3,3′-dimethyl-1,1′-(p-phenylene)diindole were also prepared from the respective 2-(phenylamino)styrene derivatives under the same conditions in reasonable yields.

A simple and efficient synthesis of isoquinoline and 3,4-dihydroisoquinoline derivatives is described. 1-Alkyl(or aryl)isoquinoline and 1-isoquinolinamine derivatives were obtained by intramolecular cyclization of 2-(2-methoxyethenyl)benzonitriles initiated by the addition of alkyl(or aryl)lithiums and lithium dialkylamides to the nitrile carbons, respectively. Synthesis of 4-aryl-3,4-dihydroisoquinolines was achieved by reactions of 2-(1-arylethenyl)benzonitriles with organolithiums, followed by aqueous workup. Treatment of the reaction mixtures with electrophiles prior to aqueous workup allowed the synthesis of 4,4-disubstituted 3,4-dihydroisoquinolines.

A convenient synthesis of 11H-indolo[3,2-c]quinolines carrying a substituent, such as 1-hydroxyalkyl, 1-alkoxyalkyl, or 1-(dialkylamino)alkyl, at the 6-position by electrophile-mediated cyclization reactions of 2-(2-isocyanophenyl)-1-methyl-1H-indole is described.

The iodoamination of o-(acylamino)styrene derivatives using iodine and sodium hydrogencarbonate, producing 7-acyl-8-iodomethylbicyclo[4.2.0]-7-azaoct-1,3,5-triene [1-acyl-2-(iodomethyl)benzazetine] derivatives, is described. Replacement of the iodo moiety by hydrogen or phenylthio group is also reported.

SummaryThe cyclooligomerization of 2,4-dialkoxybenzyl alcohols 3 catalyzed by Sc(OTf) 3 in CH 3CN under high dilution conditions produced a series of resorcin[n]arene peralkyl ethers containing four to nine resorcinol units. When the reactions were conducted at 50°C, the cyclic tetramers 4, which are thermodynamically favored products, are selectively formed in good yields. It is noteworthy that the reaction of 2,4-dimethoxybenzyl alcohol 3d at 0°C produced the corresponding cyclic octamer 8d as the major product. In other cases, such as the selective formation of a cyclic octamer could not be observed. This selective formation of 8d is due to a combination of the reversibility of the oligomerization in the presence of 3d and the insolubility of the octamer in the reaction medium. The conformational analysis of these cyclic oligomers was done by variable temperature 1H NMR spectroscopy.

A novel quinoline synthesis starting with 2-isocyanostyrene derivatives is described. The treatment of 2-isocyanostyrene derivatives with aldehydes (or acetone) in the presence of a catalytic amount of diethyl ether–boron trifluoride afforded quinoline derivatives carrying a 1-hydroxyalkyl substituent at the 2-position. The use of acetaldehyde diethyl acetal or phenyloxirane as an electrophile under the same conditions gave the corresponding quinoline derivatives, carrying the 1-ethoxyethyl or 2-hydroxy-2-phenylethyl substituent at the 2-position, respectively. 2-Isocyanostyrene derivatives reacted with N,N-dimethyliminium salts without any catalyst to give 2-(1-dimethylaminoalkyl)quinolines.

The resorcin[4]arenes bearing bromine substituents on their extraannular positions were directly prepared from 2-bromoresorcinol with aldehydes by trifluoromethanesulfonic. acid-catalyzed cyclocondensation. In each case, a single stereoisomer was isolated. The main factors for the determination of the products are the reversibility of the C-C bond formation and the difference in the solubility of the isomers.

AbstractThe crystal structures of the all-cisepimer of C-(n-propyl)calix[4]resorcinarene (1) and its caffeine complex are reported. 1 · CH3CN · H2O (2) crystallizes in the tetragonal space group P4, a= 14.3645(9), c= 9.3344(8) Å, V= 1926(2) Å3. Refinement led to a final conventional R1value of 0.047 for 3406 reflections and 236 parameters. The caffeine complex 1 · C8H10N4O2· CH3OH · H2O (3) crystallizes in the triclinic space group P1, a= 11.2892(4), b= 13.0367(8), c= 16.9700(11) Å, α = 82.902(2), β = 79.713(3), γ = 88.053(2)°, V= 2438(2) Å3. Refinement led to a final conventional R1value of 0.067 for 6393 reflections and 641 parameters. The resorcinarene displays the usual bowl shape in both compounds. The caffeine molecule in 3 is hydrogen bonded to two resorcinarene and one water molecules and one of its methyl groups is included in the cavity of a third macrocycle, suggesting CH3…π interactions. Extended hydrogen bonding patterns involving phenolic protons and solvent molecules are also present in both compounds.

1-(2-Isocyanophenyl)pyrroles have been prepared. They react in moderate to good isolated yields with aldehydes (or ketones), oxiranes, and acetals in the presence of catalytic amounts of diethyl ether–boron trifluoride to give pyrrolo[1,2-a]quinoxalines carrying an oxyalkyl substituent, such as α-hydroxyalkyl, β-hydroxyalkyl, or α-alkoxyalkyl, at the 4-position.

AbstractThe reaction of 1,3-dimethylpyrimidine-2,4,6(1H,3H,5H)-trione with various alkenes or terminal alkynes in the presence of cerium(IV) ammonium nitrate (CAN) afforded the corresponding 5,6-dihydrofuro[2,3-d]pyrimidine-2,4(1H,3H)-diones or furo[2,3-d]pyrimidine-2,4(1H,3H)-diones in moderate to good yields.

The direct synthesis of the title amino acid derivatives from carboxylic esters and nitrones can be achieved in fair to good yields when lithium or magnesium ester enolates were treated with nitrones in THF at -78 °C or in Et2O at -20 to 0 °C, respectively. The products from the reaction of t-butyl acetate with 3,4-dihydroisoquinoline N-oxide or 5,5-dimethylpyrroline 1-oxide were transformed into (1,2,3,4-tetrahydroisoquinolin-1-ylidene)acetate or (pyrrolidin-2-ylidene)acetate derivatives in the presence of triphenylphosphine, carbon tetrachloride, and triethylamine in refluxing dichloromethane.

Abstract1,3-Bis(methoxymethoxy)-2-bromomethylbenzene 3, which was prepared from 2-methylresorcinol by methoxymethylation and bromination, reacted with thiols in the presence of base to give the thioethers 4, which on treatment with HC1 in methanol produced the title compounds 5 in moderate yields.

The reaction of 2-(lithiomethyl)benzonitrile with 2-phenylthio-2-alkenoic acid derivatives in diglyme at −78 °C, followed by oxidation with sodium metaperiodate in aqueous MeOH at room temperature and the subsequent elimination reaction in refluxing toluene, gave 4-(2-cyanophenyl)-2-butenoic acid derivatives in moderate-to-fair overall yields. Intramolecular cyclization of these products using NaH in DMF at 0 °C gave 1-amino-2-naphthalenecarboxylic acid derivatives almost quantitatively. Successive treatments with an isocyanate without isolation of the aminonaphthalenecarboxylates under reflux afforded benzo[h]quinazoline-2,4(1H,3H)-diones in moderate-to-good yields.

(E)-4-Alkoxy-2-formylamino-3-butenoic acid esters have been prepared in two steps from 3-alkoxy-1-isocyanopropenes. The method is based on the reaction of 3-alkoxy-1-isocyano-1-lithiopropenes, which can be generated by the treatment of 3-alkoxy-1-isocyanopropenes with LDA in THF at −78 °C, with alkyl chlorocarbonates, affording 4-alkoxy-2-isocyano-3-butenoates. These isocyano esters have been easily transformed into the corresponding formylamino esters by treating with concd HCl in Et2O at −20 °C. Subsequently, the introduction of a substituent into the 2-position has been achieved by ethoxycarbonylation with ethyl chlorocarbonate, followed by alkylation with alkyl halides by using hexamethylphosphoric triamide (HMPA) as a co-solvent. The resulting alkylated isocyano 3-butenoates have been similarly hydrolyzed with concd HCl to the corresponding 2-formylamino-3-butenoates.

AbstractThe reactions of calix[4]resorcinarene 1 with thiols and formaldehyde in the presence of triethylamine gave tetrakis(thiomethylated)calix[4]resorcinarenes 3 in good yield. 1HNMR characterization shows that in CDCl3solution these compounds exist in a cone conformation. The presence of a circular hydrogen bonding network consisting of two types of intramolecular hydrogenbondings, OH ··· SandOH ··· OH, is indicated based on IR spectroscopy.

Treatment of 3-phenyliodonio-1,2,4-trioxo-1,2,3,4-tetrahydronaphthalenides with terminal acetylenes in the presence of a bis(triphenylphosphine)palladium chloride-cuprous iodide catalyst or cuprous oxide in N-methylpiperidine or pyridine, respectively, furnished the corresponding 2-substituted naphtho[2,3- b]furan-4,9-diones in moderate to good yields. The utility of this method was demonstrated in the synthesis of a cytotoxic natural product, 2-(1-hydroxyethyl)naphtho[2,3- b]furan-4,9-dione.

1 H-Naphtho[2,3- c]pyran-5,10-dione derivatives, including a natural product (pentalongin), were generally synthesized in one-pot using a tandem conjugate addition-cyclization sequence between 2-(1-hydroxyalkyl)-1,4-naphthoquinones and enamines (or imines). The utility of this method was demonstrated in the synthesis of pyranonaphthoquinone antibiotics, (±)-eleutherin and (±)-isoeleutherin.

The title reaction initially produced a mixture of three cyclic oligomers, calix[n]resorcinarenes (n= 4, 5, 6), as the major products. Under the conditions of their formation, the pentamer rapidly isomerized to the tetramer and the hexamer, while the hexamer slowly isomerized to the tetramer. A new cyclic oligomer, calix[5]resorcinarene, was isolated and characterized.

New acyl anion equivalents bearing a hydroxyl group at the β-position have been developed. Treatment of 3-benzyloxy-1-isocyanopropenes with lithium diisopropylamide (LDA) in THF at −78 °C generated the 1-lithio compounds, which reacted with alkyl halides to afford the corresponding 1-alkylated products in good yields. Acid hydrolysis of these alkylated products followed by hydrogenolysis of the resulting β-benzyloxyethyl ketones led to β-hydroxyethyl ketones.

Sulfoxides carrying α-hydrogens were allowed to react with magnesium amides generated in situ by the treatment of ethylmagnesium bromide with secondary amines such as 2,2,6,6-tetramethylpiperidine or diisopropylamine in diethyl ether to give the corresponding dithioacetals in moderate to good yields.

The 3+2-type cycloaddition reaction of 2-hydroxy-1,4-naphthoquinones with various alkenes or phenylacetylene was mediated by ammonium cerium(IV) nitrate (CAN) to give the corresponding naphtho[2,3-b]furan-4,9-dione and naphtho[1,2-b]furan-4,5-dione derivatives. The reaction of 2-hydroxy-1,4-benzoquinones with alkenes in the presence of CAN similarly proceeded to give benzofuran-4,7-dione and benzofuran-4,5-dione derivatives. 3-Hydroxy-1H-phenalen-1-one also underwent the CAN-mediated cycloaddition with alkenes or phenylacetylene to give the corresponding 7H-phenaleno[1,2-b]furan-7-one derivatives.

The reactions of sulfoxides with magnesium amides generated in situ from the reaction of ethylmagnesium bromide and secondary amines, such as diisopropylamine (DIPA) or 2,2,6,6-tetramethylpiperidine (TMP) in diethyl ether, were examined. Diaryl sulfoxides were heated with the diisopropylaminomagnesium reagent in diethyl ether to give the corresponding diaryl sulfides in 42—52% yields. Sulfoxides bearing hydrogens at the α-positon only (RSOCH2R1) reacted with the tetramethylpiperidinomagnesium reagent at room temperature to produce the corresponding dithioacetals (RSCHR1SR) in 47—86% yields. The treatment of sulfoxides bearing hydrogens both at the α- and β-positions (RSOCHR1CHR2R3) with the magnesium amides at room temperature afforded the corresponding vinyl sulfides (RSCR1=CR2R3) in 52—72% yields accompanying 2.3—27% yields of the corresponding dithioacetals. The pathways leading to the products involving the formation of the sulfur-stabilized carbonium ion intermediates are discussed.

4-Aryl-2-methyl(or phenyl)thio-2H-1-benzothiopyrans have been prepared in satisfactory yields from the corresponding 1-(1-aryl-2-methoxyethenyl)-2-{[methyl(or phenyl)thiomethyl]thio}benzenes via lithiation of the carbon atom between the two sulfur atoms, followed by intramolecular cyclization with loss of lithium methoxide.

The first general method for the synthesis of 4H-1,3-benzodioxin-2-one derivatives has been developed. Treatment of t-butyl 2-vinylphenyl carbonates with iodine in the presence of sodium hydrogencarbonate gave 4-iodomethyl-4H-1,3-benzodioxin-2-one derivatives in moderate to good yields. These iodides were reduced with tributyltin hydride to give the corresponding 4-methyl-4H-1,3-benzodioxin-2-one derivatives.

A magnesium amide-induced sequential conjugate addition/Claisen-type condensation between methyl 2-(methylamino)benzoate and α,β-unsaturated carboxylates has been found to provide convenient access to 4-hydroxy-1,2-dihydroquinoline-3-carboxylate derivatives and 4-oxo-1,2,3,4-tetrahydroquinoline-3-carboxylates.

The reaction of cyclopropyl phenyl sulfoxide with a magnesium amide, generated from ethylmagnesium bromide and diisopropylamine, gave 1-(phenylthio)cyclopropanol in 72% yield. When the diisopropylmagnesium reagent was treated with a thiol prior to an interaction with cyclopropyl phenyl sulfoxides, symmetrical and unsymmetrical cyclopropanone dithioacetals were produced in fair yields along with small quantities of the corresponding 1-(phenylthio)cyclopropanols.

The reactions of sulfoxides bearing a-hydrogen(s) (RSOCHR1R2: R-alkyl or aryl; R1, R2= H, alkyl, or aryl) with Grignard reagents (R3MgBr: R3= Et, Ph, or vinyl) in the presence of the diisopropylaminomagnesium reagent, generated in situ by the treatment of diisopropylamine with the appropriate Grignard reagents in diethyl ether, have resulted in the formation of the corresponding sulfides (RSCR1R2R3) in moderate to good isolated yields.

It has been found that the reactions of sulfoxides bearing hydrogen(s) at the α-position (R1SOCHR2R3: R1= alkyl or Ph; R2= H, alkyl, or Ph; R3= H or Me) with thiols (R4SH: R4= alkyl or aryl) in the presence of the (diisopropylamino)magnesium reagent, generated in situ from the reaction of ethylmagnesium bromide and diisopropylamine, in diethyl ether gave unsymmetrical dithioacetals (R1SCR2R3SR4) in isolated yields ranging from 44 to 91%.

When 2-(methylamino)benzonitrile was treated successively with magnesium bis(diisopropylamide), generated in situ from the reaction of ethylmagnesium bromide and diisopropylamine, and α,β-unsaturated carboxylic acid esters in diethyl ether at 0 °C, conjugate addition and enolate–nitrile coupling proceeded sequentially to give the corresponding 4-amino-1,2-dihydro-3-quinolinecarboxylates in isolated yields ranging from 36 to 79%.

The photomixing technique is applied to a sub-terahertz spectroscopic system with continuous-wave multimode laser diodes (CW-MLDs) to extend the spectral range. I employ two CW-MLDs which have equal spectral widths and slightly different central wavelengths, where sophisticated techniques such as external cavities are not required. I observe that photomixing causes generation of new spectral components of the signal in the frequency region of about 0.5-0.65 THz, while spectral components are limited below about 0.5 THz before the photomixing technique is applied. The generation of spectral components implies that the spectral range covered by the spectroscopic system is extended to higher-frequency regions.

The reaction of tert-butyl 2-(2-hydroxytetrahydrofuran-2-yl)acetates with alkenes in the presence of 2 equivalents of cerium(IV) ammonium nitrate (CAN) is presented. 2,3,7,8-Tetrahydrofuro[3,2-c]oxepin-4(6H)-ones were formed in moderate to fair yields via 3+2-type dihydrofuran formation, followed by lactonization.

The title benzo[b]thioxanthenequinone derivatives could be prepared in one-pot via a sequential conjugate addition and an aldol-type reaction between 1,4-naphthoquinone and o-acylbenzenethiols, followed by oxidation with 1,4-naphthoquinone or air.

A simple and efficient synthesis of 1-alkyl(or aryl)isoquinoline and isoquinolin-1-amine derivatives based on intramolecular cyclization of 2-(2-methoxyethenyl)benzonitriles initiated by the addition of alkyl(or aryl)lithiums and lithium dialkylamides to the nitrile carbons, respectively, is described.

Alkyl(or aryl)lithiums reacted efficiently with o-isocyano-ß-methoxystyrene derivatives, prepared in three steps from o-aminophenyl ketones, to afford the corresponding 2,4-disubstituted quinolines in satisfactory yields.

Reaction of 2-(1-pyrrolyl)benzaldehyde with isocyanides in the presence of a catalytic amount of boron trifluoride diethyl etherate was followed by treatment with acetic anhydride in pyridine to give the corresponding O-acetyl derivatives of 4-alkyl(or aryl)aminopyrrolo[1,2-a]quinolin-5-ols in moderate yields.