2786-31-4Relevant academic research and scientific papers
Solvent-free synthesis of benzothiazole-based quaternary ammonium salts: Precursors to ionic liquids
Nadeem, Sohail,Munawar, Munawar A.,Ahmad, Saeed,Smiglak, Marcin,Drab, David M.,Malik, Khizar I.,Amjad, Rana,Ashraf, Chaudhry M.,Rogers, Robin D.
, p. 19 - 37 (2010)
A series of 13 benzothiazolium iodide salts have been prepared in solvent-free conditions by optimizing the reaction. An additional 26 benzothiazolium salts with bistrifluoromethanesulfonimide and trifluoromethylsulfonate were prepared via simple metathesis reactions from the iodide precursors. Out of a total of 39 prepared salts, 26 were identified as ionic liquids, with melting points as low as 42 °C observed for dodecylbenzothiazolium bistrifluoromethanesulfonimide. All prepared compounds have been characterized using FTIR, 1H, 13C NMR, and HRMS analyses. The thermal stabilities as well as melting points of these salts were also analyzed.
Study of the Effect of N-Protonation and N-Methylation on the 1H and 13C Chemical Shifts of the Six-Membered Ring in Benzazoles and 2-Substituted N,N-Dimethylamino Derivatives
Benassi, Rois,Grandi, Romano,Pagnoni, Ugo M.,Taddei, Ferdinando
, p. 415 - 420 (1986)
The 1H and 13C NMR spectral data of benzimidazole, benzoxazole, benzothiazole and N-methylbenzimidazole and of their 2-N,N-dimethylamino derivatives are reported.The spectra were recorded in acetone-water solution.The chemical shifts of these molecules are compared with those of the corresponding cations obtained by N-protonation and N-methylation of the neutral molecules.The carbon atoms C-4, C-5, C-6 and C-4a show a qualitatively identical behaviour, moving to higher field when the cations are formed from the benzazoles examined, but a different behaviour is found for C-2, C-7 and C-7a, which depends on the heterocyclic ring, on the presence of the substituent in position 2 and on the type of cation formed (N-protonation and N-methylation cause different effects).The conversion of benzazoles into the corresponding cations causes all 1H chemical shifts to move to lower field.KEY WORDS: Heterocycles, Benzazoles, Amino Derivatives, Cation formation, 1H and 13C NMR
Base induced synthesis of 4H-1,4-benzothiazines and their computational studies
Preet, Simer,Cannoo, Damanjt Singh
, p. 79232 - 79238 (2015)
A one pot synthesis of 1,4-benzothiazines from 1,3-benzothiazolium cations and α-haloketones through ring expansion under ultrasonication was carried out by employing optimal 5% sodium hydroxide and characterization was done with the help of various spectroscopic techniques viz. NMR, IR and mass spectrometry. Single crystal X-ray diffraction and computational studies of (4-bromophenyl)(4-methyl-4H-benzo[b][1,4]thiazin-2-yl)methanone (3c) were also performed. Different concentrations of different bases (NaOH, Na2CO3, NaHCO3 solutions etc.) were used to obtain 1,4-benzothiazine derivatives. But, the best results were obtained with 5% NaOH solution (3.7 equivalents) for the synthesis of single product 1,4-benzothiazine derivatives while, with other concentrations, the reaction did not proceed to a single product. Quantum chemical calculations were done to find the optimized geometry and to correlate the experimental and calculated values of the bond parametres and 13C NMR chemical shifts of the synthesized compound. The optimized geometry was obtained using density functional theory (DFT) with the basis set 6-31G(d). The theoretical values of the 1H NMR chemical shifts were in agreement with the experimental values. The photophysical properties of some of the synthesized compounds were studied with the help of ultraviolet-visible and fluorescence spectroscopy.
Synthesis and Characterization of Thiazepine/Benzothiazepine Derivatives Through Intramolecular C-2 Ring Expansion Pathway
Preet, Simer,Cannoo, Damanjt Singh
, p. 296 - 302 (2017)
A facile and highly efficient one-pot synthesis of novel thiazepine and benzothiazepine derivatives was established by ring expansion. With a greener methodology (ultrasonication), a polysubstituted ring system with the thiazepine core moiety can be easily synthesized from simple and easily available reactants in good yields. Moreover, the synthesized compounds show fluorescence and also antioxidant activity.
Carbene-catalyzed aerobic oxidation of isoquinolinium salts: Efficient synthesis of isoquinolinones
Wang, Guanjie,Hu, Wanyao,Hu, Zhouli,Zhang, Yuxia,Yao, Wei,Li, Lin,Fu, Zhenqian,Huang, Wei
supporting information, p. 3302 - 3307 (2018/07/29)
A mild and environmentally friendly carbene-catalyzed aerobic oxidation of isoquinolinium salts was successfully realized. Accordingly, a diverse set of isoquinolinones and phenanthridinones was efficiently prepared in good to excellent yields. The mechanistic study indicates that the formation of an aza-Breslow intermediate is the crucial step in this transformation. This reaction features ambient air as the sole oxidant and oxygen source, a broad substrate scope, and excellent functional-group tolerance and proceeds under mild reaction conditions. Furthermore, a highly efficient synthesis of bioactive molecules and natural products including N-methylcrinasiadine, N-isopentylcrinasiadine, N-phenethylcrinasiadine, isoindolo[2,1-b]isoquinolin-5(7H)-one, PJ-34, rac-Gusanlung D, rosettacin, 8-oxopseudopalmatine and ilicifoline B was accomplished.
Highly reactive (<1 min) ratiometric probe for selective 'naked-eye' detection of cyanide in aqueous media
Goswami, Shyamaprosad,Manna, Abhishek,Paul, Sima,Aich, Krishnendu,Das, Avijit Kumar,Chakraborty, Shampa
, p. 1785 - 1789 (2013/05/09)
We have designed and synthesized a triphenyl aminebenzothiazole coupled receptor (TBH) that exhibits a selective, sensitive, colorimetric, and ratiometric rapid response toward cyanide anion in aqueous media. The sensing event is explained by spectroscopy along with DFT calculation and CV diagram. Sensor displays a very fast response (- and AcO- in aqueous media.
Formation and crystallographic elucidation of stable [4 + 2]-coordinate nickel(ii) N,S-heterocyclic carbene (NSHC) complexes
Ding, Nini,Zhang, Jun,Hor, T. S. Andy
experimental part, p. 1853 - 1858 (2009/08/08)
A series of square-planar N,S-heterocyclic carbene (NSHC) complexes trans-[NiX2(N-RBzTh)2] (BzTh = benzothiazolin-2-ylidene) (R/X = Bz/Br; Me/I; Et/I; Pri/I; Bui/I) have been synthesized and characterized by X-ray single-crystal diffraction analysis. These are the first crystallographically established NSHC complexes of nickel in the literature. The N,S-heterocyclic carbene (NSHC) rings invariably twist away from co-planarity with the metal coordination plane such that the N-substituent moves on top and below the metal to facilitate electrostatic γ-hydride interaction, thus giving an essentially [4 + 2] coordination at the Ni(ii) center. These compounds are active toward reductive Ullmann-type coupling reactions in Bu4NBr showing higher activities towards bromoanisole or bromotoluene than bromobenzene. The complex trans-[NiI2(N-Pr iBzTh)2] with the shortest Ni...H anagostic separation and a near-ideal orthogonal orientation between the carbene and metal planes gives the highest yields.
Reactivity of the Thiazolium C2 Ylide in Aprotic Solvents: Novel Experimental Evidence for Addition Rather Than Insertion Reactivity
Chen, Yao-Tsung,Jordan, Frank
, p. 5029 - 5038 (2007/10/02)
Two thiazolium compounds were synthesized specifically labeled at their C2 positions: 3,4,5-trimethylthiazolium nitrate and 3-benzyl-5-(β-ethoxyethyl)-4-methylthiazolium bromide, with a view to examine their pathways leading to dimerization in strongly basic medium using 13C NMR.On addition of less than 1 equiv of base the N-methyl ion first formed an unsymmetrical dimer in which the C2 atoms of two molecules were bonded to each other and only one of them still carried a hydrogen; that unsymmetrical dimer upon addition of excess base lost the remaining hydrogen at C2 and was converted to a mixture of syn and anti symmetrical dimers in nearly equal amounts.The sequence of observations on addition of base to the N-methyl derivative is consistent with nucleophilic addition of the conjugate base to a second thiazolium ion at its C2 position.Since the unsymmetrical dimer is formed first, rather than the symmetrical dimer, the latter cannot result from direct dimerization of two conjugate bases (ylides) by a carbene mechanism.Instead, a carbanion-addition mechanism was further supported by two experiments.A "crossover" experiment was designed in which unsymmetrical dimers were detected in Me2SO on addition of limiting potassium tert-butoxide to thiazolium ions containing -H and -D, under conditions such that there was little H/D exchange observed at the C2 position.Also, N-3-alkenylthiazolium ions were synthesized, that, if carbenic reactivity had existed, would have resulted in formation of cyclopropanes.In preference to the intramolecular reaction, intermolecular unsymmetrical dimers resulted in each case, consistent with nucleophilic addition.On addition of base to the N-benzylthiazolium ion, the first product to be detected by 13C NMR was the syn/anti symmetrical dimer mixture (again bonded via the C2 atoms), that underwent a -sigmatropic rearrangement of one of the benzyl groups from N3 to C2.According to 1H NMR recorded within minutes of mixing, the unsymmetrical dimer precedes the symmetrical one for this salt as well.The reactivity of the C2 ylide derived from the N-methyl and N-benzylthiazolium ions can be rationalized according to an ionic addition reaction, implying that the related thiamin (vitamin B1) conjugate base (ylide) behaves similarly.
Nonacidic and Highly Chemoselective Protection of the Carbonyl Function. 3-Methylbenzothiazolines as a Base- and Acid-Resistant Protected Form for the Carbonyl Groups
Chikashita, Hidenori,Komazawa, Shun-ichiro,Ishimoto, Nishiki,Inoue, Koji,Itoh, Kazuyoshi
, p. 1215 - 1225 (2007/10/02)
A simple and useful new type of protection method for carbonyl groups by conversion into 3-methylbenzothiazoline derivatives with o-(methylamino)benzenethiol was describe.With this method, 3-methylbenzothiazolines were conveniently obtained in excellent yields from various aldehydes and ketones.This method allows efficient protection and deprotection under mild and neutral conditions and affords protection of the carbonyl group against both basic and acidic conditions.The difference in reactivity between different carbonyl groups was successfully utilized for the chemoselective benzothiazolination of the formyl group of 4-oxopentanal and also for the chemoselective conversion of 4-androstene-3,17-dione and progesteron into the corresponding benzothiazolines with the nonconjugated keto groups remaining intact. 2-Substituted benzothiazolines derived from aldehydes were efficiently converted into 2,2-disubstituted benzothiazolines via alkylation, with a varity of Grignard or organolithium reagents, of 2-substituted 3-methylbenzothiazolium salts which were readily obtained by the treatment of the former thiazolines with trityl perchlorate in acetonitrile.These salts were also obtained in good yields from aldehydes in one-pot syntheses by the treatment with o-(methylamino)benzenethiol in acetonitrile followed by addition of trityl perchlorate. 3-Methylbenzothiazolium iodide was found to be also effective as a formyl cation equivalent and the reactions with Grignard or organolithium reagents produced the corresponding 2-substituted benzothiazolines in good yields.With this reaction, 2-deutero-3-methylbenzothiazolium iodide was effectively applied as a deuterated formyl cation equivalent for the synthesis of aldehyde-d.
Carbon Transfer Reactions with Heterocycles: Part II - Carbon Transfer Reactions of Thiazolidines and Benzothiazolines
Singh, Harjit,Sarin, Rakesh,Singh, Kamaljit
, p. 132 - 134 (2007/10/02)
Thiazolidines (2) and benzothiazolines (3) transfer their C-2 unit at carbonyl group oxidation level to nucleophiles but reactions of 3 are attended by oxidation to benzothiazoles.
