Synthesis of oligonucleotides containing thiazole and thiazole N-oxide nucleobases

[reaction: see text] The thiazole C-nucleoside analogue was synthesized by the Hantzsch cyclization method to form the thiazole ring and was then converted to the thiazole N-oxide C-nucleoside analogue by peracid oxidation of the heterocycle nitrogen. Incorporation of the thiazole and thiazole N-oxide phosphoramidites into DNA was successful though significant deoxygenation of the N-oxide occurred during DNA assembly. The mechanism proposed for the reduction of the thiazole N-oxide to thiazole involves the formation of an N-oxide phosphite ester.     

Beiträge zum Studium einiger Heterocyclen. L—Massenspektrometrische Untersuchungen von 2-Aryl-4-r-5-acetylthiazolen

The mass spectra of some 5-acetyl thiazoles were studied, and the differences emphasized between them and the corresponding 4-acetyl derivatives. This could constitute a method for their identification. The nature of the substituent in position 4 of the thiazole influences the fragmentation patterns of thiazole ring. In the case of 4-hydroxymethyl derivatives, a skeletal rearrangement occurs before fragmentation.     

Bromination of 4-(2-thienyl)thiazoles and 2-(2-thienyl)quinoline

Depending on the substituent, the bromination of 4-(2-thienyl)thiazoles and 2-(2-thienyl)quinoline takes place in the 5 position of the thiophene or thiazole ring. When an amino group is present in the 2 position of the thiazole ring, bromination takes place in the 5 position of the thiazole ring. When excess brominating agent is present, a second bromine atom enters the 5 position of the free ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 35–38, January, 1982.     

Synthesis of Ethyl 8‐Aryl‐8‐hydroxy‐3‐oxo‐8H[1,2,4]oxadiazolo‐[3,4‐c][1,4]thiazine‐5‐carboxylates by Ring‐Expansion Rearrangement

The title compounds were prepared by the ring–ring interconversion of ethyl 5‐nitroso‐6‐arylimidazo[2,1‐b]thiazole‐3‐carboxylates with hydrochloric acid. The effect of electron‐withdrawing substituent in the thiazole ring on the general applicability of the ring–ring interconversion has been also evaluated.     

Pd-catalyzed selective decarboxylation/C–H activation coupling of aryl acid with thiazole and oxazole directed by 1,2,3-triazole

An efficient palladium-catalyzed selective decarboxylation/C–H activation coupling of aryl acid with thiazole and oxazole under the assistance of 1,2,3-triazole ring were developed. This work provides an effective access to build functionalized 1,2,3-triazoles bearing thiazole and oxazole moieties. This method has good substrate compatibility to compose a series of selective heterocyclic compounds in moderate to good yields.     

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.     

An efficient method for the synthesis of 2-thiazoleacetic acid N-sulfonyl amidines

Chemistry of Heterocyclic Compounds - A three-step method was designed and developed on the basis of retrosynthetic analysis for the synthesis of hybrid molecules containing a thiazole ring and an...     

The electron impact-induced fragmentation of 2-arylthiazoles

The mass spectrometric fragmentation of 2-aryl thiazoles centres, like that of simple thiazoles, around the cleavage of the 1,2 and 3,4 bonds of the thiazole ring. One characteristic species does arise from the fission of the 1,5 and 2,3 bonds, viz. a thiobenzoyl ion. The fragmentations of some substituents at the 4 and 5 positions of the thiazole ring, prior to ring cleavage, are also described.     

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.     

Unusual product from the acid-catalyzed one-pot,multicomponent reaction of thiocarbohydrazide,aldehydes, and phenacyl bromides

A one-pot, three-component protocol for the synthesis of novel five-membered thiazole ring bonded to two hydrazone motifs is described. The acid-catalyzed reaction of one equivalent of thiocarbohydrazide, two equivalents of aromatic aldehydes, and one equivalent of phenacyl bromides afforded the five-membered thiazole ring. The reactions proceed with novel chemoselectivity. Similar reported protocols have always afforded 1,3,4-thiadiazines.     

Electrolytic partial fluorination of organic compounds. 64.(1) Anodic mono- and difluorination of thiazolyl sulfides

The anodic fluorination of 2-thiazolyl methyl sulfide, 2-thiazolyl propargyl sulfide, and 2-thiazolyl acetonyl sulfide was successfully carried out to provide the corresponding 5-fluorothiazole and 2,5,5-trifluorothiazoline derivatives. The latter products were readily hydrolyzed to give isolable 5,5-difluoro-2-hydroxythiazoline derivatives. On the other hand, anodic fluorination of 2-thiazolyl cyanomethyl sulfide afforded 5-fluorothiazole and alpha-fluorinated thiazole derivatives. Thus, the product selectivity was found to be greatly changed by the electron-withdrawing ability of substituents at the side chain of the thiazole ring. This is the first report of a successful anodic fluorination of a thiazole ring.     

噻唑类化合物应用研究新进展

噻唑环是一类重要的含氮硫杂原子的五元芳杂环,其特殊的结构使得噻唑类化合物在化学、药学、生物学和材料科学等诸多领域具有广阔的应用前景,显示出巨大的开发价值,受到广泛关注.本文结合作者的研究工作,参考国内外近五年文献,系统地综述了噻唑类化合物在医药、农药、材料、生物染色剂和超分子化学领域应用研究进展.     

Synthesis of 2‐Aminothiazole Derivatives in Easy Two‐Step,One‐Pot Reaction

Condensation of brominated ethyl acetoacetate with thiourea gives 2‐amino‐5‐ethoxycarbonyl‐4‐methylthiazole ( 1 ) and ethyl α‐(2‐amino‐4‐thiazolyl)acetate ( 2 ), indicating that bromination of the substrate occurs on both sides of the carbonyl group. X‐ray diffraction studies indicate weak hydrogen bonds of the amino groups, which are not observed in the IR spectra. The 1 molecule adopts planar S,O‐anti conformation in the crystal lattice, whereas the methylene group, insulating thiazole ring and the ester group in 2 molecule, makes it more flexible and makes the ester group nearly perpendicular to the thiazole ring. The small deviations of the bond lengths and angles indicate mesomeric interaction between complementary substituents across the thiazole ring.     

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.     

Thiazolocyanines

Some results of an investigation of thiazolocyanines containing-hetaryl residues attached to the nitrogen atoms of the thiazole ring are summed up. The effect of the nature of these residues, their basicities, and mainly the steric hindrance generated by them on the absorption of the dyes was investigated. The angles of rotation of the hetaryl residues about their bond with the nitrogen atom of the thiazole ring in the dyes both in the presence and absence of substituents in the thiazole ring were calculated, and the associated disruption of the planarity of the thiazolotrimethylidynecyanine molecules is examined.See [1] for communication XVII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1609–1613, December, 1975.     

Synthesis of Heterocyclic Analogs of α‐aminoadipic Acid and its Esters Based on Imidazo[2,1‐b][1,3]Thiazole

A method for the preparation of heterocyclic analogs of α‐aminoadipic acid and its esters based on the imidazo[2,1‐b][1,3]thiazole ring system was developed. In this method, free‐radical bromination of ethyl 6‐methylimidazo[2,1‐b][1,3]thiazole‐5‐carboxylate with NBS afforded a versatile building block, ethyl 6‐bromomethylimidazo[2,1‐b][1,3]thiazole‐5‐carboxylate. Coupling of ethyl 6‐bromomethylimidazo[2,1‐b][1,3]thiazole‐5‐carboxylate with Schöllkopf's chiral auxiliary followed by acidic hydrolysis generated ethyl 6‐[(2S)‐2‐amino‐3‐methoxy‐3‐oxopropyl]imidazo[2,1‐b][1,3]thiazole‐5‐carboxylate. A similar procedure using diethyl (Boc‐amino)malonate yielded racemic 2‐amino‐3‐[(5‐ethoxycarbonyl)imidazo[2,1‐b][1,3]thiazol‐6‐yl]propanoic acid.     

Quantum chemical study of penicillin: Reactions after acylation

The density functional theory methods were used on the model molecules of penicillin to determine the possible reactions after their acylation on β‐lactamase, and the results were compared with sulbactam we have studied. The results show that, the acylated‐enzyme tetrahedral intermediate can evolves with opening of β‐lactam ring as well as the thiazole ring; the thiazole ring‐open products may be formed via β‐lactam ring‐open product or from tetrahedral intermediate directly. Those products, in imine or enamine form, can tautomerize via hydrogen migration. In virtue of the water‐assisted, their energy barriers are obviously reduced. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Theoretical studies of sulbactam: Reactions after acylation

DFT methods were used on the model molecular to determine the mechanism of β‐lactamase inhibitor. The results show that the thiazole ring can be opened as well as β‐lactam ring. The thiazole ring‐open product can be formed via β‐lactam ring‐open product or tetrahedral intermediate directly. Those products, in imine or enamine form, can tautomerize via hydrogen migration. The sulforious form products may be transformed into sulfonyl ones. Water or hydroxyl group in residues on active site will help lower the activation energy of above reactions, and if structure permitted, they also effect the route selection of whole reaction system. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

A base induced fragmentation of tetramisole

The exposure of dl-2,3,5,6-tetrahydro-6-phenylimidazo[2,1-6 Jthiazole (tetramisole) to lithium diisopropylamide in tetrahydrofuran ruptures the thiazole ring to give, following the introduction of primary or secondary alkyl halides, 1-(2′-alkylthio)ethyl-4-phenylimidazoles. Conclusive evidence for the thiazole ring opening was obtained by a single crystal x-ray diffraction study of 1-(2′-p-bromobenzylthio)ethyl-4-phenylimidazole.     

Efficient access to 5-substituted thiazoles by a novel metallotropic rearrangement

A novel rearrangement process involving the migration of trimethylstannanyl or trimethylsilanyl groups around the thiazole ring provides access to either 2- or 5-metallated thiazoles by tuning the reaction conditions. The proposed mechanism, based on experimental evidence, is characterized by the catalytic role of thiazole bisadducts as metal-transfer agents.