Studies on 2-Aminothiophenes: Synthesis,Transformations, and Biological Evaluation of Functionally-Substituted Thiophenes and Their Fused Derivatives

Abstract

Heterocyclic enamines1 reacted with ethyl acetoacetate to afford the corresponding amide derivatives2. Treatment of2 with carbon disulphide yielded the dipotassium salts3which reacted in-situ with a variety of α -haloketones to give the respective substituted thiophenes5,8, and13. The reactivity of the latter products towards various chemical reagents was studied to yield their fused thiophene derivatives7,10,12, and14, respectively. Some representative compounds were tested for antimicrobial activity.     

Convenient synthesis of N-(4-(2-aminopyridin-4-yl)thiazol-2-yl)-2-phenylacetamides

We report a facile one-pot, three-step synthesis of N-(4-(2-aminopyridin-4-yl)thiazol-2-yl)-2-phenylacetamides via condensation of 2-p-methoxybenzylamino-4-acetylpyridine with phenylacetylthioureas.     

Ca2[BN2]H: The First Nitridoborate Hydride — Synthesis,Crystal Structure,and Vibrational Spectra

Ca₂[BN₂]H was synthesized from a mixture of the binary components Ca₃N₂, CaH₂ and BN (molar ratio 1 : 1 : 2) in a sealed steel ampoule encapsulated in an evacuated silica tube at 1273 K. Ca₂[BN₂]H crystallizes in the orthorhombic space group Pnma (no. 62) with a = 9.2015(8)Å, b = 3.6676(2)Å and c = 9.9874(12)Å (Z = 4; Pearson symbol oP24). The crystal structure is a filled variant of the Co₂P type and can be formulated as Co₂P(□^t)₃(□^py)₃ ≡ Ca₂[N—B—N]H(□^t)₂(□^py)₃ (□^t and □^py = tetrahedral and square‐pyramidal hole, respectively). The d(B—N) bond lengths and bond angle for the linear [N—B—N]^3— anion are: d(B—N1) = 1.324(3)Å, d(B—N2) = 1.350(2)Å and ∠N—B—N = 177.2(2)°. The vibrational spectra of Ca₂[BN₂]H confirm the presence of [N—B—N]^3— groups deviating only slightly from the ideal D_∞h symmetry. The vibrational frequencies and the ?(B—N) force constants are discussed and compared with those of the isotypic compound Ca₂[BN₂]F.     

Direct Conversion of 3-(2-Nitroethyl)-1H-Indoles into 2-(1H-Indol-2-yl)Acetonitriles

The recently discovered [4+1]-spirocyclization of nitroalkenes to indoles provided a convenient new approach to 2-(1H-indol-2-yl)acetonitriles. However, this reaction was complicated by the formation of inert 3-(2-nitroethyl)-1H-indole byproducts. Herein, we offer a workaround this problem that allows for effective transformation of the unwanted byproducts into acetonitrile target molecules.     

Short Review on the Synthesis of Thiophene,Pyrazole, and Thiazole Derivatives

The review summarizes the synthesis of different thiophene, pyrazole, and thiazole derivatives by refluxing 9a in ethanol with a catalytic amount of TEA or leaving it in DMF containing potassium carbonate at room temperature overnight to afford the corresponding thiophene derivative 10a . In addition, cyclization of Schiff bases with thioglycollic acid in the presence of a catalytic amount of ZnCl₂ yielded novel thiophene derivatives. Condensation of 2‐substituted‐4‐methylythio semi‐carbazides 92 with carbonyl compounds under strong acidic conditions afforded 2‐thiazolines. Also, carboxylic acid reacted with 2‐thioethylamine in the presence of triphenylphosphine and triethylamine to afford 2‐thiazolines 98 .     

Syntheses,Structural Characterization,Reactivity, and Theoretical Studies on Some Heteroligand Oxoperoxotungstate(VI)

White microcrystalline diamagnetic oxoperoxotungstate(VI) complexes K[WO(O₂)₂F]·H₂O, K₂[WO(O₂)₂(CO₃)]·H₂O, [WO(O₂)(SO₄)(H₂O)₂] have been synthesized from reaction of Na₂WO₄·2H₂O with aqueous HF, solid KHCO₃, aqueous H₂SO₄ (W:F⁻ 1:3; W: CO₃ ^{2 −} 1:1; and W: SO₄ ^{2 −} 1:3), and an excess of 30% H₂O₂ at pH 7.5–8. Precipitation was completed by the addition of precooled acetone. The occurrence of terminal WO and triangular bidentate O₂ ^{2 −}(C _{2 v} ) in the synthesized compounds was ascertained from IR spectra. The IR spectra also suggested that the F⁻ and SO₄ ^{2 −} ions in K[WO(O₂)₂F]·H₂O and [WO(O₂)(SO₄)(H₂O)₂] were bonded to the WO ⁺⁴ center in monodentate manner, while CO₃ ^{2 −} ion in K₂[WO(O₂)₂(CO₃)]·H₂O binds the metal center in bidentate chelating fashion. The complex [WO(O₂)(SO₄)(H₂O)₂] is stable upto 110°C. The water molecule in [WO(O₂)(SO₄)(H₂O)₂] is coordinated to the WO ⁺⁴ center, whereas it occurs as water of crystallization in the corresponding peroxo(fluoro) and peroxo(carbonato) compounds. Mass spectra of the compounds are in good agreement with the molecular formulae of the complexes. K₂[WO(O₂)₂(CO₃)]·H₂O acts as an oxidant for bromide in the aqueous‐phase bromination of organic substrates to the corresponding bromo‐organics, and the complex also oxidizes Hantzsch‐1,4‐dihydropyridine to the corresponding pyridine derivative in excellent yield at room temperature. Density functional theory computation was carried out to compute the frequencies of relevant vibrational modes and electronic properties, and the results are in agreement with the experimentally obtained data.     

Solar thermochemical reactions Ⅱ: Synthesis of 2-aminothiophenes via Gewald reaction induced by solar thermal energy

Green conditions have been developed for the synthesis of substituted 2-aminothiopbenes employing multicomponent reactions of a ketone with active methylene nitrile and elemental sulphur induced by free solar thermal energy.     

Ruthenium monoterpyridine complexes with 2,6-bis(benzimidazol-2-yl)pyridine: Synthesis,spectral properties and structure

Ruthenium monoterpyridine complexes with the tridentate 2,6-bis(benzimidazol-2-yl)pyridine (LH₂), [Ru(trpy)(LH₂)]²⁺, [1]²⁺ and [Ru(trpy)(L²⁻)], 2 (trpy = 2,2′:6′,2″-terpyridine) have been synthesized. The complexes have been authenticated by elemental analyses, UV–Vis, FT-IR, ¹H NMR spectra and their single crystal X-ray structures. Complexes [1]²⁺ and 2 exhibit strong MLCT band near 475 and 509 nm, respectively, and are found to be very much dependent on solution pH. The successive pH dependent dissociations of the N–H protons of benzimidazole moiety of LH₂ in [1]²⁺ lead to the formation of 2. The proton induced inter-convertibility of [1]²⁺ and 2 has been monitored via UV–Vis spectroscopy and redox features. The two pK_a values, 5.75 and 7.70, for complex [1]²⁺ have been determined spectroscopically.     

Highly efficient, multigram and enantiopure synthesis of (S)-2-(2,4′-bithiazol-2-yl)pyrrolidine

(S)-2-(4-Bromo-2,4′-bithiazole)-1-(tert-butoxycarbonyl)pyrrolidine ((S)-1) was obtained as a single enantiomer and in high yield by means of a two-step modified Hantzsch thiazole synthesis reaction when bromoketone 3 and thioamide (S)-4 were used. Further conversion of (S)-1 into trimethyltin derivative (S)-2 broadens the scope for further cross-coupling reactions.     

One Pot,Multi-component Synthesis of 3-[（4-Aryl-thiazol-2-yl）-hydrazono]-1,3-dihydro-indole-2-one

A series of 3-[（4-phenyl-thiazol-2-yl）-hydrazono]-1,3-dihydro-indole-2-one（4a-4g） and 3-{[4-（2-oxo2H-chromen-3-yl）-thiazol-2-yl]-hydrazono}-1,3-dihydro-indol-2-one（6a-6d） has been prepared in a one-step procedure from condensation reaction of isatin（1）,thiosemicarbazide（2） and bromoacetophenones（3）/or 3-（2-bromoacetyl）coumarins（4）.The method provides a simple and efficient route to prepare the compounds in good yields and in a short experimental time as compared to its stepwise procedure.     

亲电硫试剂参与的2-芳基-3-硫代-2,3-二氢喹啉-4(1H)-酮的合成研究

本文报道了以(E)-1-(2-对甲苯磺酰胺基)-3-芳基丙-2-烯-1-酮(1)为底物与N-硫代丁二酰亚胺(2)通过亲电环化反应合成2-芳基-3-硫代-2,3-二氢喹啉-4(1H)-酮类化合物。以三氟化硼乙醚为催化剂(20 mol %),1,2-二氯乙烷为溶剂,反应温度为60 _oC,可以60-92%的收率得到一系列2-芳基-3-硫代-4(1H)-喹啉酮衍生物,化合物3a-k均未见文献报道,其结构均经过₁H NMR, ₁₃C NMR以及高分辨质谱进行确定。     

微流控芯片中高效合成苯基二吡咯-2-基甲烷的研究

微流控芯片是近年发展起来的一种新型的微反应器.在微流控芯片中以HCl为催化剂常温下合成了苯基二吡咯-2-基甲烷,考察了反应物流速、催化剂浓度、吡咯与苯甲醛的比例对苯基二吡咯-2-基甲烷产率的影响.通过在催化剂溶液中加入离子液体[bmim]BF4明显地提高了反应效率,苯基二吡咯-2-基甲烷的产率可以达到95%以上.采用本法大大减少了试剂用量和条件试验阶段的实验成本.     

Ruthenium monoterpyridine complexes with 2,6-bis(benzoxazol-2-yl)pyridine as an ancillary ligand: Synthesis,structure and spectral studies

Ruthenium monoterpyridine complexes, [1]⁺ and [2]²⁺, with 2,6-bis(benzoxazol-2-yl)pyridine as an ancillary ligand, L, have been synthesized and characterized by UV–Vis, FT-IR and ¹H NMR spectroscopic techniques. The formulations of the complexes were confirmed by the single crystal structure of their perchlorate salts. In both complexes, the Ru^II center is hexa-coordinated in a distorted geometry. In complex [1]⁺, the ancillary ligand L behaves as a bidentate ligand; in [2]²⁺, however, it binds the metal center as a tridentate ligand. The central pyridine nitrogen of terpyridine (N_p,trpy) is in a cis position with respect to the central pyridine nitrogen of the ancillary ligand (N_p,benz) in complex [1]⁺ and in a trans-position in complex [2]²⁺. The cis orientation of N_p,trpy and N_p,benz in complex [1]⁺ forces L to behave as bidentate. The quasi-reversible Ru^II/Ru^III couple appears at 0.90 and 1.44 V versus SCE in the case of complex [1]⁺ and [2]²⁺, respectively. [1]⁺, in the presence of aqueous AgNO₃, affords [2]²⁺ through an intramolecular dissociative interchange pathway.     

含有二氢吡唑环的新三唑类化合物的设计与合成

设计并合成了１０种含有二氢吡唑环的新三唑类化合物，对新化合物结构进行了确证，讨论了二氢吡唑环的成环方式，所合成的化合物均具有一定的生物活性。     

Synthesis of 3,3,5,5-tetrabenzyl-1,2,4-trithiol and 1,2-dis(1,3-arylpropan-2-yl)disulfane

Novel sulfur-containing compounds (3a-3c, 4a-4c) were obtained in ethanol with 1,3-diphenyl-2-propanone as the starting material. The advantages of this procedure were mild reaction conditions, simple protocol, and high yields. The structures of the products were characterized by IR, 1H NMR, MS and elementary analysis. The crystal of the new compound 4a belongs to monoclinic, space group C2 with a = 18.727(3), b = 6.5179(9), c = 13.7576(18)Å, β = 131.0610(10)°, V = 1266.2(3)Å3, Z = 2, Dc = 2.136 g/cm3, μ = 1.078 mm-1, F(0 0 0) = 843, R = 0.0490 and wR = 0.1247 for 3211 observed reflection with I > 2σ(I). X-ray analysis reveals that the molecule is not symmetrical, the molecular structure is stabilized by weak π-π stacking interactions, and no classical hydrogen bonds can be observed.     

Microwave-assisted synthesis of 2-aminothiophene-3-carboxylic acid derivatives, 3H-thieno[2,3-d]pyrimidin-4-one and 4-chlorothieno[2,3-d]pyrimidine

A two-minute microwave irradiation allowed the synthesis of several 2-aminothiophene-3-carboxylic acid derivatives. Their efficient transformation to thieno[2,3-d]pyrimidin-4-one and the corresponding 4-chloro derivative is also reported under microwave irradiation.     

钴-杂环偶氮试剂配合物中钴存在型体的研究

2-(5-溴-2-噻唑偶氮)-5-二乙氨基苯酚(HL)或2-(2-苯并噻唑偶氮)-5-磺丙氨基苯酚(H_2L’)与钴(Ⅱ)反应和氧化形成的Co(Ⅱ)L_2和CO(Ⅲ)L_2·Cl或Co(Ⅱ)L_2’·(TBA)2和Co(Ⅱ)L_2’·TBA在C_(18)硅氧烷键合相和乙醇-氯仿或乙腈-水流动相之间分配。不同实验条件下取得的HPLC图上的不同色谱峰表明,最初形成的是不稳定的钻(Ⅱ)配合物,但很快被溶液中的氧氧化为稳定的钴(Ⅲ)配合物,KIO_4等强氧化剂和加热均可加速氧化。与迅速制备钴配合物所得的可见吸收光谱相比,放置一段时间或加热或加入强氧化剂所得的吸收光谱明显红移,由此确证配合物中不稳定的钴(Ⅱ)型体和稳定的钴(Ⅲ)型体的存在。电泳实验中配合物向正或负电极的移动也确证了两种钴型体的存在。