Fries reaction and dakin rearrangement in benzo-2,1,3-thiadiazoles

The Fries rearrangement of 4- and 5-acetoxybenzo-2,1,3-thiadiazoles has given 4-hydroxy-7-acetyl- and 5-hydroxy-4-acetylbenzo-2,1,3-thiadiazoles, which on oxidation afford mixtures of 5-chloro-4,7-dioxo- and 5,6-dichloro-4,7-dioxobenzo-2,1,3-thiadiazole and of 6-chloro-4,5-dioxo- and 6,7-dichloro-4,5-dioxobenzo-2,1,3-thiadiazole. Reaction of 6,7-dichloro-4,5-dioxobenzo-2,1,3-thiadizole with ortho-phenyl-enediamine gives 4,5-dichloro-2,1,3-thiadiazolo[4,5-a]phenazine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1683–1687, December, 1987.     

Oxidation of halohydroxybenzo-2,1,3-thiadiazoles with nitric acid

4,5-Dioxobenzo-2,1,3-thiadiazole has been synthesized. Its structure was proven by conversion to the known 4,5-dioximinobenzo-2,1,3-thiadiazole and to 2,1,3-thiadiazolo[4,5-a]phenazine, and by reduction to 4,5-dihydroxybenzo-2,1,3-thiadiazole. Oxidation of 5,6-dichloro-4,7-dihydroxy- and 5,7-dichloro-4-hydroxy-benzo-2,1,3-thiadiazoles forms 5,6-dichloro-4,7-dihydroxybenzo-2,1,3-thiadiazole, of known structure, and 7-chloro-4,5-dioxobenzo-2,1,3-thiadiazole; the latter by reaction with ortho-phenylene diamine is converted to 4-chloro-2,1,3-thiadiazolo[4,5-a]phenazine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 850–852, June, 1987.     

Oxidation and reduction of some derivatives of benzo-2,1,3-thiadiazole

In the reduction of 4-hydroxy-7-phenylazobenzo-2,1,3-thiadiazole and of 4-hydroxy-7-nitro-benzo-2,1, 3-thiadiazole with sodium hydrosulfite, 7-amino-4-hydroxybenzo-2,1,3-thiadiazole is obtained. The reduction of 4-hydroxybenzo-2,1,3-thiadiazole leads to 2,3-diaminophenol which forms 5-hydroxyquinoxaline with the bisulfite derivative of glyoxal. The oxidation of 4-hydroxy- and 4-aminobenzo-2,1,3-thiadiazoles with potassium dichromate in an acid medium has yielded 4,7-dioxo-4,7-dihydrobenzo-2,1,3-thiadiazole, which has been converted into 4,7-dihydroxybenzo-2,1,3-thiadiazole and 4,7-di(hydroxyimino)-4,7-dihydrobenzo-2,1,3-thiadiazole.Translated from Khimiya Geterotsikliches-kikh Soedinenii, No. 7, pp. 926–929, July, 1973.     

Interconversion of benzofurazandione monoximes

The preparation of 5-hydroxy-4-nitroso- and 7-hydroxy-4-nitrosobenzofurazan as well as of their 6-chloro and methyl derivatives is described and the oxime structure of these compounds is established. NMR spectra of benzofurazan-4,5-dione-4-monoxime and benzofurazan-4,7-dione-4-monoxime show evidence for an interconversion, in solution, of two monoximes, the 4,5- and 4,7-derivative prevailing in organic solvents and aqueous alkaline media, respectively. Chloro and methyl derivatives of benzofurazan-4,5- and 4,7-dione-4-monoximes show a similar interconversion in organic solvents.     

Synthesis of aminomethyl derivatives of 3-methyl-4,7-dihydro-3H-imidazo[4,5-d][1,2,3]triazin-4-one

New aminomethyl derivatives of 3-methyl-4,7-dihydro-3H-imidazo[4,5-d][l,2,3]triazin-4-one were synthesized by Mannich reaction. These Mannich bases is also possible to prepare by reaction of 7(5)-hydroxymethyl-3-methyl-4,7(5)dihydro-3H-imidazo[4,5-d][l,2,3]triazin-4-one with amines. The compounds obtained exist in solutions as mixtures of N⁵ and N⁷ isomers, and the fraction of the latter grows with the polarity of the solvent.     

Conversion of 4-substituted benzo-2,1,3-thiadiazoles to 5-chloro-4,7-dioxobenzo-2,1,3-thiadiazole by action of hydrogen peroxide and hydrochloric acid

Under the influence of hydrogen peroxide and hydrochloric acid in acetonitrile 4-substituted benzo-2,1,3-thiadiazoles form 5-chloro-4,7-dioxobenzo-2,1,3-thiadiazole. 4-Alkoxy- and 4-[(alkoxycarbonyl)methoxy]benzo-2,1,3-thiadiazoles give, in addition, the corresponding 5,7-dichloro derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 114–117, January, 1988.     

Researches on 2,1,3-thia-and selenadiazole

Chlorination of benzo-2,1,3-thiadiazole (I) in the presence of iron and paraform gives only 4-chlorobenzo-2,1,3-thiazole. Chlorination of 5,6-dimethylbenzo-2,1,3-thiadiazole (II) under exactly the same conditions gives only 5,6-dimethyl-4,7-dichlorobenzo-2,1,2-thiadiazole. Similarly chloromethylation of II in the presence of paraform gives only 5,6-dimethly-4,7-di(chloromethyl)benzo-2,1,3-thiadiazole. Chlorination and chloromethylation of I proceed through the intermediate formation of monosubstituted compounds which change into disubstimted ones.It is known [2,3] that Chlorination of benzo-2,1,3-thiadiazole (I) and its 5,6-dimethyl derivative (II) with chlorine in the presence of iron gives mainly the 4,7-dichloro substitution products III and IV respectively.It was previously shown [4] that chloromethylation of I with dichlorodimethyl ether in the presence of anhydrous aluminum chloride also gives mainly 4,7-di(chloromethyl)benzo-2,1,3-thiadiazole (V). Bases and pseudo-bases (paraform, urotropine. dimethylformamide) have a retarding effect on chloromethylation. When the reaction is run in the presence of these latter the products comprise besides V, 4-chloromethyl-2,1,3-thiadiazole (VI), or else, if enough base is added, there is no reaction.For Part XLII see [1].     

Benzoid-quinoid tautomerism of Schiff bases and their structural analogs: LV. Crown-containing N-phenylimines derived from ortho-hydroxycarbaldehydes of the coumarin series

Schiff bases were synthesized from 3-hydroxy-6-oxo-6H-benzo[c]chromene-4-carbaldehyde, 5-hydroxy-4,7-dimethyl-2-oxo-2H-chromene-6-carbaldehyde, 6,7-dihydroxy-4-methyl-2-oxo-2H-chromene-8-carbaldehyde, 5,7-dihydroxy-4-methyl-2-oxo-2H-chromene-6,8-dicarbaldehyde, and 5-hydroxy-4,7-dimethyl-2-oxo-2H-chromene-6,8-dicarbaldehyde and (¹⁵N)aniline or aminobenzo-15-crown-5 (2,3,5,6,8,9,11,12-octahydrobenzo[b][1,4,7,10,13]pentaoxacyclopentadecin-15-amine), and tautomeric equilibrium between the hydroxy enimino and keto enamino forms of the 4- and 8-iminomethyl derivatives in solution was revealed by 1H NMR and electronic spectroscopy. Addition of alkaline earth cations to their solutions in acetonitrile displaced the tautomeric equilibrium toward the hydroxy enimino structure due to complex formation with the crown ether fragment.     

Photophysical and electrochemical properties of π-extended molecular 2,1,3-benzothiadiazoles

The reaction of 4,7-dibromo-2,1,3-benzothiadiazole with arylboronic acids (phenyl, 1-naphthyl, 4-methoxyphenyl, 4-chlorophenyl and 4-trifluoromethylphenyl) in the presence of catalytic amounts of a NCP-pincer palladacycle affords photoluminescent π-extended 4,7-diaryl-2,1,3-benzothiadiazoles 4a-e in high yields. These 4,7-diaryl-2,1,3-benzothiadiazoles exhibit high fluorescent quantum yields, high electron affinities and adequate band gap values for testing as OLEDs. The 4,7-bis-naphthyl-2,1,3-benzothiadiazole 4b presents two different lifetimes (bi-exponential decay) due to the presence of two atropisomers. The Sonogashira coupling reaction of 4,7-diethynyl-2,1,3-benzothiadiazole 6 with the corresponding halo-aryl compounds (iodobenzene, 1-bromonaphthalene, 4-iodoanisole, 4-bromo-N,N-dimethylaniline and 2-bromopyridine) afforded the photoluminescent π-extended 4,7-bis-alkynylaryl-2,1,3-benzothiadiazoles 7a-e, also in high yields. These 4,7-diethynyl-2,1,3-benzothiadiazoles also present high fluorescent quantum yields, high electron affinities and adequate band gap values for testing as OLEDs. The 4,7-disubstituted-2,1,3-benzothiadiazoles 4a-e and 7a-e exhibit different electrochemical behavior. The presence of two ethynyl spacers in 2,1,3-benzothiadiazoles 7a-e shifts the reduction potentials to less cathodic values and also results in two well-defined and distinct reduction processes.     

1-Hydroxy- and 1-nitroso-2,5-dimethylpiperid-4-ones and their derivatives

Derivatives of 1-hydroxy-2,5-dimethylpiperid-4-one substituted at the hydroxy and the carbonyl groups have now been prepared and the IR spectra of some of them have been studied. 1-Nitroso-2,5-dimethylpiperid-4-one has been prepared from 2,5-dimethylpiperid-4-one and subjected to various reactions at the nitroso- and the carbonyl groups. The IR spectra of the N-nitroso-compounds prepared are discussed.     

基于PCPDTBT复合材料的制备及光致电荷转移

合成了PCPDTBT,通过NMR,GPC等方法对聚合物进行了表征.研究了聚合物的热学与电化学性质.采用溶液法将电子给体PCPDTBT与两种电子受体1-(3-甲氧基羰基)丙基-1-苯基[6,6]C61(PCBM)和ZnO纳米粒子分别进行了复合,通过研究复合前后的荧光变化,确认了给体-受体两相界面间发生了由分子能级差引发的光致电荷转移.这些研究结果为探索性能更佳的有机太阳能电池材料体系提供了重要的参考依据.     

Synthesis and characterization of new linear pi-conjugated molecules containing bis(ethynylpyridine) units with a benzothiadiazole spacer

Three novel 4,7-bis(n-pyridylethynyl)-2,1,3-benzothiadiazoles (n = 2, 3, and 4) were synthesized by using the Sonogashira cross-coupling reaction of 4,7-dibromo-2,1,3-benzothiadiazole with the corresponding ethynylpyridines in the presence of a Pd(II) catalyst. The viologen analogues were also prepared by methylation of pyridyl nitrogen atoms. X-ray structure analysis of these compounds revealed the linear molecular structures with unusual columnar crystal structures. Insertion of a benzothiadiazole moiety into the acetylene-pyridine skeleton brings about a large increase in electron affinity and the bispyridyl compounds obtained here show high fluorescence quantum yields.     

Effect of allylic strain on the conformations of diphenyl-substituted tetrahydro-1,3-oxazin-2-ones and hexahydropyrimidin-2-ones

The conformations of the cis and trans isomers of 4,6-diphenyl-, 4,5-diphenyl- and 5,6-diphenyltetrahydro-1,3-oxazin-2-one and 4,5-diphenylhexahydropyrimidin-2-one, and of some of their N-substituted derivatives, have been studied by ¹H NMR. Conformers with 4a, 6e-, 4a, 5e- and 5a, 6e-phenyl groups are preferred in the respective isomers of the N-H oxazinones, confirming a half-chair conformation of the ring. Allylic strain caused by N-substituents shifts strongly the a,e?e, a equilibria in trans-4,6-diphenyl- and cis-4,5-diphenyl-oxazinones, but only moderately the e,e?a,a equilibria in the compounds with trans-vicinal phenyl groups. In the latter, the diaxial conformation is preferred only in the case of bulky N-substituents. The diaxial conformation is more favoured in the trans-4,5-diphenylpyrimidones.     

Synthesis of 3‐phenyl‐5‐(trifluoromethyl)isoxazole and 5‐phenyl‐3‐(trifluoromethyl)isoxazole

Reaction of 4,4,4‐trifluoro‐1‐phenyl‐1,3‐butanedione with hydroxylamine led to the formation of 5‐hydroxy‐3‐phenyl‐5‐(trifluoromethyl)‐4,5‐dihydroisoxazole which was dehydrated to 3‐phenyl‐5‐(trifluoro‐methyl)isoxazole. This isomer can also be synthesized by reaction of 4‐chloro‐4‐phenyl‐1,1,1‐trifluoro‐3‐buten‐2‐one with sodium azide. The regioisomer, 5‐phenyl‐3‐(trifluoromethyl)isoxazole was synthesized by reaction of 1,1,1‐trifluoro‐4‐phenylbut‐3‐yn‐2‐one with hydroxylamine and by the reaction of 3‐chloro‐1‐phenyl‐4,4,4‐trifluorobut‐2‐en‐1‐one with sodium azide. Both isomers were characterized by mass and NMR spectroscopy.     

Regioselective N‐Alkylation of Ethyl 4‐Benzyloxy‐1,2,3‐triazolecarboxylate: A Useful Tool for the Synthesis of Carboxylic Acid Bioisosteres

Acidic 4‐hydroxy‐1,2,3‐triazole is a proven bioisostere of acidic functions that has recently been used to replace the acidic moieties of biologically active leads. Straightforward chemical strategies for the synthesis of the three possible N‐alkylated 4‐hydroxy‐1,2,3‐triazole regioisomers have been designed and reported herein, by identifying the optimal conditions under which the alkylation of ethyl 4‐benzyloxy‐1,2,3‐triazolecarboxylate (compound 19 ) can be regiodirected to the triazole N(b) position and thus produce the only isomer that cannot be obtained via the cycloaddition reaction. Furthermore, an innovative platform for parallel synthesis, called Arachno and which has been patented by the authors' group, has been used to speed up the process, and an NMR study has been carried out to better understand the reactivity of compound 19 towards the N(b) position. A library of benzyloxy protected 4‐hydroxy‐1,2,3‐triazoles has been prepared using the two strategies: regiodirection for the N(b) and N(c) isomers and cycloaddition for the N(a) isomers; the processes are described herein. The three N‐alkylated regioisomer series have been characterized spectroscopically (NMR and MS). The subsequent catalytic hydrogenation of the 4‐benzyloxy protective group on the N‐alkylated‐4‐benzyloxy‐5‐ethoxycarbonyl‐1,2,3‐triazoles provided the corresponding substituted 4‐hydroxy‐1,2,3‐triazoles.     

On the synthesis of siloxanes. XXIV. Nucleophilic substitution reactions of 2-functional 1,3-dioxa-2-4,7-trisilacylcloheptanes and 1,3-dioxa-2,4,8-trisilacyclooctanes

2-Hydrogen-1,3-dioxa-2,4,7-trisilacycloheptanes and 2-hydrogen-1,3-dioxa-2,4,8-trisiacyclooctanes, each as a mixture of three configurational isomers, were synthesized and halogenated with chlorine and bromine in the presence of pyridine. The stereochemical course of the halogenation reactions was studied by gas chromatography. 2-Chloro-2,4,7-trimethyl-4,7-bis(trimethyl-siloxy)-1,3-dioxa-2,4,7-trisiacycloheptanes and 2-chloro-2,4,7-trimethyl-4,7-diphenyl-1,3-dioxa-2,4,7-trisilacycloheptanes reacted with alcohols in the presence of pyridine, triethylamine, or 2,6-dimethylpyridine. Gas chromatography, and¹H NMR and²⁹Si NMR spectroscopy were used to investigate the stereochemistry of these substitution reactions. It has been found that all reactions proceed with retention of configuration and that the differences of the relative reactivities of the configurational isomers were distinctly smaller than those observed for reactions of the configurations isomers of functional cyclotrisiloxanes.     

Synthesis and structural assignment of some N-substituted imidazopyridine derivatives

A synthesis of all possible N-alkylated 2-n-butyl-imidazo[4,5]pyridine isomers is described as well as their structural assignment by ¹H NMR spectroscopy. One of these derivatives, 2,-n-butyl-3-[2′- (1H-tetrazol-5-yl)-4-biphenylylmethyl]-3H-imidazo[4,5-b]pyridine 9 is a potent angiotensin II receptor antagonist.     

Synthesis of imidazo[4,5-d]pyridazine nucleosides related to inosine

Several imidazo[4,5-d]pyridazine nucleosides which are structurally similar to inosine were synthesized. Anhydrous stannic chloride-catalyzed condensation of persilylated imidazo[4,5-d]-pyridazin-4(5H)one (1) and imidazo[4,5-d]pyridazine-4,7(5H,6H)dione ( 16 ) with 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribofuranose ( 3 ) provided (after sodium methoxide deblocking) 6-β-D-ribo furanosylimidazo[4,5-d]pyridazin-4(5H)one (5) and 3,6-di-(β-D-ribofuranosyI)imidazo[4,5-d]pyridazin-4-one ( 7 ); and 1-(β-D-ribofuranosyl)imidazo[4,5-d]pyridazine-4,7(5H,6H)dione ( 19 ) and 1,5 or 6-di-(β-D-ribofuranosyl)imidazo[4,5-d ]pyridazine-4,7(5H or 6H)dione ( 21 ), respeeitvely. 4,7-Diehloro-1-β-D-ribofuranosylimidazo[4,5-d]pyridazine ( 12 ) and dimethyl 1-β-D-ribofuranosylimidazole-4,5-dicarboxylate ( 26 ), both prepared from stannic chloride-catalyzed ribosylations of the corresponding heterocycles, were converted in several steps to 3-β-D-ribo-furanosy limidazo[4,5-d]pyridazin-4(5H)one ( 14 ) and nucleosidc 19 , respectively. Acid-catalyzed isopropylidenation of mesomeric betaine 7 or nuclcoside 14 provided 3-(2,3-isopropylidene-β-D-ribofuranosyl)imidazo[4,5-d]pyrizin-4(5H)one ( 31 ). 1-β-D-Ribofuranosylimidazo[4,5-d]-pyridazine ( 29 ) was obtained in several steps from nueleoside 12 . The structure of the nucleosides was established by the use of carbon-13 and proton nmr.     

Study of electrophilic substitution and oxidation reactions of 4- and 5-hydroxybenzo-2,1,3-selenadiazoles

The halogenation, nitrosation, and oxidation of 4- and 5-hydroxybenzo-2,1,3-selenadiazoles have been studied, as has the acetylation of these hydroxy compounds and their halogen and nitroso derivatives. The structure of the resulting compounds has been demonstrated, and it has been found that the nitroso-substituted derivatives exist primarily in the tautomeric oxime form.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1135–1140, August, 1992.     

Synthesis and structure‐property relationship of new donor–acceptor‐type conjugated monomers and polymers on the basis of thiophene and benzothiadiazole

We have synthesized three new donor–acceptor‐type monomers to achieve soluble and processable low‐band gap polymers, 4,7‐bis(4‐octyl‐2‐thienyl)‐2,1,3‐benzothiadiazole (B4TB), 4,7‐bis(3‐octyl‐2‐thienyl)‐2,1,3‐benzothiadiazole (B3TB), and 4‐(3‐octyl‐2‐thienyl)‐7‐(4‐octyl‐2‐thienyl)‐2,1,3‐benzothiadiazole (B34TB), by the Suzuki coupling reaction. Using B4TB and B3TB, two soluble high molecular weight regioregular head‐to‐head and tail‐to‐tail polymers poly[4,7‐bis(4‐octyl‐2‐thienyl)‐2,1,3‐ benzothiadiazole] (PB4TB) and poly[4,7‐bis(3‐octyl‐2‐thienyl)‐2,1,3‐benzothiadiazole] (PB3TB) were prepared via iron(III) chloride‐mediated oxidative polymerization. The structures of the polymers were confirmed by ¹H and ¹³C NMR, and the molecular weights were determined by size exclusion chromatography. The optical properties (absorbance and fluorescence) of the monomers and polymers were studied and compared with unsubstituted analogues. The monomers and polymers bearing octyl substituents on the thiophene rings pointing away from the benzothiadiazole units (B4TB and PB4TB) possess a more planar structure, and their optical spectra appear redshifted as compared with those having the octyl chain nearer to the benzothiadiazole (B3TB and PB3TB). The optical band gaps of PB3BT (E_g = 2.01 eV) and PB4BT (E_g = 1.96 eV), however, are at much higher energy levels than that of the unsubstituted electrochemically polymerized PBTB material (E_g = 1.1–1.2 eV) as a result of steric effects of the octyl chains. The electrochemical properties of the monomers and polymers were examined using cyclic voltammetry and reflect the effect of alkyl substitution. B4TB and PB4TB were oxidized at a lower potential than B3TB and PB3TB, whereas their reduction potentials were less negative. The electrochemical band gap calculated from the onset of the reduction and oxidation process agreed with the optical band gap calculated from the absorption edges. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 251–261, 2002