Theoretical Study on Second‐order Nonlinear Optical Properties of Substituted Thiazole Derivatives

On the basis of ZINDO program, we have designed a program to calculate the nonlinear second‐order polarizability β_yk and β_μ according to the SOS expression. The second‐order nonlinear optical properties of 4‐nitro‐4′‐dimethylamino‐stilbene and a series of its thiazole derivatives were studied. The calculated results were that: When replacing a benzene ring in 4‐nitro‐4′‐dimethylamino‐stilbene by a thiazole ring, the influence on β values depends on the position of thiazole ring. When the thiazole ring connects with nitro group (acceptor), the β values increase significantly compared with corresponding stilbene derivatives. The β values of 2‐(p‐donor‐β‐styryl)‐5‐nitro‐thiazole derivatives (2–7) are larger than those of 2‐(p‐nitro‐β‐styryl)‐5‐donor‐thiazole derivatives (8–13) and 2‐(p‐donor‐phenyl)‐azo‐5‐nitro‐thiazole derivatives (14–19). The 2‐(p‐donor‐β‐styryl)‐5‐nitro‐thiazole derivatives (2–7) are good candidates as chromophores duo to their high nonlinearities and potential good thermal stability.     

Pyrroloindoles. 5. Acetylation of 1H,6H-pyrrolo[2,3-e]indole by means of the Vilsmeier-Haack reaction

The Vilsmeier-Haack reaction with 1H,6H-pyrrolo[2,3-e]indole with the participation of dimethylacetamide was studied. 3-Acetyl, 8-acetyl, 2-acetyl, and 3,8-diacetyl derivatives (with great preponderance of the 3-acetyl derivative) were obtained. The formation of a 2-substituted product does not have an analogy in the chemistry of indole. On the basis of data from the IR and PMR spectra it was established that an intramolecular hydrogen bond between 1-H and the C=O group in the 8 position exists in the 8-acetylpyrroloindole molecule. This bond also affects the mass-spectral fragmentation of the 8-acetyl derivative.See [1] for communication 4.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 206–211, February, 1982.     

Beiträge zum Studium einiger Heterocyclen. XLIV—Massenspektrometrische Untersuchungen einiger 2-(p-X-Phenyl)-5-Y-4-acetylthiazole

The fragmentation under eletron impact of some new 2-phenyl-4-acetyl-thiazoles has been studied. The compounds investigaed exhibit molecular ion peaks. Substituents in the para position of the bensene ring do not influence the fragmentation patterns but only the relative abundances of the molecular ion and some fragment ions. However, by introdicing CI and Br in position 5 of the thiazole some signifiecant differences appear (‘ortho effect’). A rearrangement also occurs involving a 5-membered cyclic transition state. Intense doubly charged ions are obseved a fact which is attributed to the presence of two easily ionizable centres.     

3-碘-苯并吡喃-4-酮与硫脲类反应的研究

3-碘-苯并吡喃-4-酮(1)与硫脲发生Micheal加成反应, 合成三个2-硫代-5-(2-羟基苯甲酰基)咪唑衍生物和五个2-亚氨基-5-(2-羟基苯甲酰基)噻唑衍生物。这些化合物结构经核磁共振光谱、红外光谱和元素分析均予以证实。     

Die massenspektrometrische retro-Diels-Alder-Reaktion: 1, 2, 3, 4-Tetrahydroisochinolin und 1, 2, 3, 4-Tetrahydronaphthalin (Tetralin). 31. Mitteilung über massenspektrometrische Untersuchungen

The Mass Spectral retro-Diels-Alder-Reaction: 1,2,3,4-Tetrahydroisoquinoline and 1,2,3,4-Tetrahydronaphthaline (Tetraline) The retro-Diels-Alder reaction of 1,2,3,4-tetrahydroisoquinoline and of its N-acetyl derivative was confirmed on the basis of labelled derivatives (Scheme 2). Furthermore, the loss of ethylene was investigated with the 1,2,3,4-tetrahydronaphthalene- and 1,2,3,4-tetrahydronaphthalen-1-one-derivatives given in Schemes 4, 5 and 6. In the case of the 1,2,3,4-tetrahydronaphthalen-1-one-derivatives ethylene is lost via a retro-Diels-Alder reaction. The loss of ethylene from 1,2,3,4-tetrahydronaphthalene ( 1 ) and from its derivatives is a rather complex reaction (Scheme 8): 1/3 of ethylene is split off 1 ⁺ via a formal retro-Diels-Alder reaction, 2/3 are lost after a specific rearrangement. The ratio of these two fragmentation pathways depends very much on the substituents placed at the aliphatic and the aromatic rings, compare e.g. Table 4.     

Synthesis of new 2-pyridinone and thiazole derivatives containing coumarin moiety

Coumarin has shown considerable therapeutic potency because of its versatile biological prosperities. Also, pyridines have been adopted in medicinal chemistry as potent ring. Moreover, several investigations reported the potency of thiazole-containing compounds. So, during this research, new functionalized 2-pyridinone and thiazole derivatives bearing coumarin moiety were aimed to synthesize. Many trials to obtain the 6-amino-2-oxo-pyridine-3,5-dicarbonitriles through the condensation of cyanoacetohydrazone of 3-acetyl coumarin with 2-(arylidene)malononitriles were carried out using different reaction conditions. In all cases, the reaction gave none of the corresponding 2-pyridinone derivatives except the reaction with 2-(benzylidene)-malononitrile afforded product in few yield. Moreover, the reaction of another cyanoacetanilide with the 2-(arylidene)-malononitrile afforded the unexpected arylidene derivatives rather than the expected pyridin-2-one derivatives. Finally, new thiazoles bearing coumarin moiety were synthesized using 3-acetylcoumarin N-(2,4-dimethoxyphenyl)-thiosemicarbazone. Cyclization of thiosemicarbazone derivative with ethyl 2-chloroacetate, chloroacetone or phenacyl bromide afforded in high yields the corresponding derivatives of thiazolidin-4-one, 4-methylthiazole or 4-phenylthiazole, respectively.     

Synthesis and biological evaluation of new 2-aryl-4-((4-aryl-1H-1,2,3-triazol-1-yl)methyl)thiazole derivatives

Research on Chemical Intermediates - A series of 2-aryl-4-((4-aryl-1H-1,2,3-triazol-1-yl)methyl)thiazole derivatives (8a–p) have been synthesized. The structure of the newly synthesized...     

Transformations of methyl L-(—)-thiazolidine-4-carboxylate, 2-amino-2-thiazoline and 2-aminothiazole into thiazoloazines and azolothiazoles

In the search for potential immunomodulators methyl L-(—)-thiazolidine-4-carboxylate (2), 2-amino-2-thiazoline (12), and 2-aminothiazole (19) were transformed into derivatives of various bicyclic systems. Thus, from compound 2 derivatives of perhydrothiazolo[3,4-a]pyrazine 4 and 5, perhydrothiazolo[4,3-c]-[1,4]oxazine 7, and perhydroimidazo[1,5-c]thiazole 9a,b, from compound 12 derivatives of 2,3-dihydro-thiazolo[2,3-b]pyrimidine 13a,b , and from compound 19 derivatives of imidazo[2,1-b]thiazole 21, 22, 24, and 25 were prepared. 6-(p-Sulfamoylphenyl)-7-oxoperhydroimidazo[1,5-c]thiazole-5-thione (9a) was found to exhibit immunorestoration activity.     

Synthesis of 4-(4-Methylsulfonylphenyl)-3-phenyl-2(3H)-thiazole Thione Derivatives as New Potential COX-2 Inhibitors

Synthesis of novel 4-（4-methylsulfonylphenyl）-3-phenyl-2（3H）-thiazole thione derivatives with functionalized diarylheterocycle pharmacophore as potential COX-2 inhibitors was described. The title compounds were synthesized by cyclocondensation of corresponding dithiocarbamate and 2-bromo-1-（4-methylsulfonylphenyl）ethanone, followed by dehydration with H2SO4. All of the target compounds were characterized by ^1H NMR, IR and mass spectral data.     

Mass spectra of derivatives of imidazo[2,1-b] thiazole and thiazolo[3,2-a]benzimidazole

The mass spectra of 6-phenylimidazo[2,1-b]thiazole, thiazolo[3,2-a]benzimidazole, and a number of thiazole-ring-substituted derivatives were investigated. The fragmentation of both groups of compounds commences with cleavage of the bonds in the thiazole ring and leads to the appearance of nitrogen- and sulfur-containing fragments in the spectra. The common character of the mass spectrometric disintegration of the investigated compounds indicates that they have similar electronic structures. The mass number and position of a substituent in the thiazole ring can be determined on the basis of the mass numbers of a series of fragments.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 778–783, June, 1974.     

Mass spectra of partially n-acetylated derivatives of kanamycin a

As part of a program concerned with the chemistry and biochemistry of aminocyclitol antibiotics, a number of selectively N-acetylated kanamycins have been prepared from kanamycin monosulfate and characterized by a study of the electron impact induced fragmentation of two types of derivatives. In one of these, the remaining free amino groups were N-trideuteroacetylated and the N-acylated kanamycins thus obtained, were N.O-methylated. The spectra of these derivatives were useful for the location of the N-acetyl and N-trideu-teroacetyl groups, except in the 2-deoxystreptamine unit. In a second type of derivative, the partially N-acetylated kanamycins were N.O-permethylated converting the free amino groups into dimethylamino groups. In this form, it was possible to locate the site of N-aeelylation on the 2-deoxystreptamine ring. The partially N-acetylated kanamycins have been identified as 1,3,6'-tri-N-acetyl, 3,6',3'-tri-N-acetyl, 3,6'-di-N-acetyl, 1,6'-di-N-acetyl and 6'-N-acetyl kanamycin, from a study of the mass spectra of these two types of derivatives.     

Synthesis and biological evaluation of new 4‐(4‐(1‐benzyl‐1H‐1,2,3‐triazol‐4‐yl)phenyl)‐2‐phenylthiazole derivatives

A novel series of 4‐(4‐(1‐benzyl‐1H‐1,2,3‐triazol‐4‐yl)phenyl)‐2‐substitutedthiazole derivatives ( 8a‐l) have been synthesized by [3 + 2] cycloaddition reaction of 4‐(4‐ethynylphenyl)‐2‐substitutedthiazole with substituted benzyl azide in aqueous DMF. Starting compounds 4‐(4‐ethynylphenyl)‐2‐substitutedthiazole ( 6a‐d ) were synthesized by reaction of 4‐(2‐substitutedthiazol‐4‐yl)benzaldehyde with Ohira‐Bestmann reagent in methanol. The structures of these novel triazole‐thiazole clubbed derivatives were confirmed by the spectral analysis. The title compounds ( 8a‐l ) were tested for antimycobacterial activity against Mycobacterium tuberculosis H37Ra active and dormant (MTB, ATCC 25177) and antimicrobial activity against standard Gram‐positive bacteria, Staphylococcus aureus (NCIM 2602) and Bacillus subtilis (NCIM 2162), and Gram‐negative bacteria, Escherichia coli (NCIM 2576) and Pseudomonas flurescence (NCIM 2059). Compounds 8a , 8b , 8c , and 8h reported good activity against B subtilis, compounds 8a , 8b , and 8c showed good activity against S aureus, and compound 8b showed good activity against dormant M tuberculosis H37Rv strain. Compounds 8b and 8c found more potent against Gram positive and dormant M tuberculosis H37Rv strains. These novel triazole‐thiazole clubbed analogues found to be a capable leads for further optimization and development.     

Efficient palladium(II)-catalyzed homocoupling of thiazole-4-carboxylic or oxazole-4-carboxylic derivatives

An efficient Pd(OAc)₂-catalyzed homocoupling of thiazole-4-carboxylic or oxazole-4-carboxylic derivatives is described. It represents a facile and practical methodology to prepare bis-5,5′-thiazole (oxazole)-4,4′-dicarboxylic derivatives in good to excellent yields. This protocol tolerates a series of substitutions on the thiazole (oxazole) rings, including alkyl, carbonyl, and electron-withdrawing/donating group substituted phenyl groups.     

Nitration of 2- and 4-[2-(2-furyl)vinyl]thiazole derivatives

Nitration of 4-methyl-2-[2-(nitro-2-furyl)vinyl]thiazole with a mixture of concentrated nitric and sulfuric acids leads to 4-methyl-5-nitro-2-[2-(3,5-dinitro-2-furyl)vinyl]thiazole. Under the same conditions 2-methyl- and 2-acetamido-4-[1-R-2-(5-nitro-2-furyl)vinyl]thiazoles (R=CH₃, Cl) are nitrated in the 3 position of the furan ring, 2-amino-4-[1-chloro-2-(5-nitro-2-furyl)vinyl]thiazole is nitrated in the 5 position of the thiazole ring and 2-acetamido-5-nitro-4-[2-(2-furyl)vinyl]thiazole undergoes profound changes. Under the influence of a mixture of of nitric acid and acetic anhydride the latter compound is converted quantitatively to the 5-nitro derivative (with respect to the furan ring), whereas 4-[2-(5-nitro-2-furyl)vinyl]thiazole derivatives do not undergo reaction.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 314–317, March, 1977.     

Substituent Effects on the Photochromic Properties of Benzothiophene‐Based Derivatives

Five diarylethene photochromic derivatives, the structures of which incorporate a central benzothiophene unit, a left‐hand thiazole group, and a right‐hand benzothiophene group, have been prepared. The compound with a thiazole unit with no substituent on the reaction‐center carbon atom reveals an unprecedented transformation upon light irradiation. When the 4‐position of thiazole is protected by a methyl group, the compounds show high photosensitivity and photochromic properties. In this case, light irradiation affords new compounds with [5]helicene structures featuring the highest redshifted absorption maxima reported to date.     

Acetylation of 6-alkyl-5-ethoxycarbonyl-2-hydroxy-4-methyl-dihydropyrimidines and their 2-mercapto analogs

A number of 6-alkyl- and 6-aryl-5-ethoxycarbonyl-2-hydroxy-4-methyldihydropyrimidines and their 2-mercapto analogs and the acetyl derivatives of these compounds have been synthesized. In each case, two isomeric acetyl derivatives were obtained, probably the 1- and 3-acetyl compounds.     

Structural characterization of trimethylsilyl methyl glycosides derivatives by high-resolution mass spectrometry,linked scans and MIKE experiments

Gas chromatography–mass spectrometry investigations have been carried out for the structural analysis of trimethylsilyl methyl derivatives of keto-deoxy sugars and sialic acids studied under electron ionization. Fragmentation patterns were determined. The three derivatives undergo some common fragmentation pathways. Formation of fragment ions possessing cyclic resonance-stabilized structures was demonstrated. As the sialic acid derivative contained a N-acetyl substituent, some additional fragmentations occurred and were also elucidated. Thus, the mechanism of fragmentation was revealed for these derivatives and new findings concerning some series of fragment ions are presented. Presented at the Annual French National Symposium on Mass Spectrometry, Electrophoresis and Proteomics, 20–23 September 2007 in Pau, France.     

Catalysis by zeolite leading to the construction of thiazole ring: an improved synthesis of 4-alkynyl substituted thiazoles

Zeolite H-beta facilitated the reaction of α-chloro acetyl chloride with 1,2-bis-trimethyl silyl acetylene to give 1-chloro-4-(trimethylsilyl)but-3-yn-2-one which on treatment with thioacetamide afforded 2-methyl-4-[(trimethylsilyl)ethynyl]thiazole. l-Proline on the other hand facilitated the coupling reaction of 2-methyl-4-[(trimethylsilyl)ethynyl]thiazole with (hetero)aryl halides (modified Sonogashira reaction) under Pd-Cu catalysis in the presence of aqueous K₂CO₃ affording an improved method for the synthesis of corresponding 4-alkynyl substituted thiazole derivatives.     

Thiazolecarboxylic Acid Derivatives. 1. N-Substituted 2-Amino-4-methylthiazole-5-carboxylic Acid Derivatives

Acylation of the ethyl ester and anilide of 2-amino-4-methylthiazole-5-carboxylic acid gave 2-acetyl(arylsulfonyl)amino derivatives. Methylation of acetylaminothiazole and subsequent deacetylation gave 2-methylamino-4-methylthiazole-5-carboxylic acid, which was then converted into esters. The ethyl ester and anilide of thiazole-2-carboxylic acid were used as starting compounds for the synthesis of 2-dimethylaminoformimino- and 2-chlorobenzenesulfonylureido derivatives.     

Azulene‐1‐azo‐2′‐thiazoles. Synthesis and properties

Several derivatives belonging to a new compound class, namely azulene‐1‐azo‐2′‐thiazoles, were prepared by the diazotization of 2‐aminothiazoles in the presence of HNO₃/H₃PO₄ followed by the coupling of diazonium salts with azulenes in buffered medium. The reactions proved to be general for this class, the yields are, however, considerably influenced by the substituents at thiazole moiety. For the first time a N‐oxide provided from an amino substituted five‐member nitrogenous heterocycle was diazotized and coupled. The structure of the obtained compounds was assigned and their physico‐chemical properties were discussed. The new azulene azo derivatives exhibit a strong bathochromic shift in UV‐Vis due to the intense push‐pull effect of aromatic system and to the intrinsic properties of thiazole moiety.