Benzothiazoline Derivatives Research Articles

Radical Hydroalkylation and Hydroacylation of Alkenes by the Use of Benzothiazoline under Thermal Conditions.

The hydroalkylation and hydroacylation of electron-deficient alkenes proceeded smoothly by using benzothiazoline derivatives as radical-transfer reagents under thermal conditions without light irradiation or any additive. Both benzyl and benzoyl moieties were transferred efficiently.

Benzothiazolines as radical transfer reagents: hydroalkylation and hydroacylation of alkenes by radical generation under photoirradiation conditions.

Novel radical transfer reagents under photoirradiation conditions were developed by the use of benzothiazoline derivatives. These reagents enabled both hydroalkylation and hydroacylation of alkenes under neutral conditions at ambient temperature without any toxic reagents or an excess amount of metals. A mechanistic study was carried out to elucidate the radical process.

Solvent-Free Synthesis and Safener Activity of Sulfonylurea Benzothiazolines.

A series of novel sulfonylurea benzothiazolines was designed by splicing active groups and bioisosterism. A solvent-free synthetic route was developed for the sulfonylurea benzothiazoline derivatives via the cyclization and carbamylation. All compounds were characterized by IR, 1H-NMR, 13C-NMR, HRMS. The biological activity tests indicated the compounds could protect maize against the injury caused by chlorsulfuron to some extent. The molecular docking result showed that the new compound competed with chlorsulfuron to bind with the herbicide target enzyme active site to attain detoxification.

ChemInform Abstract: Synthesis and Free Radical Scavenging Activity of Coumarin Derivatives Containing a 2‐Methylbenzothiazoline Motif.

AbstractReaction of coumarin derivatives with aminothiophenols affords the benzothiazoline derivatives (III) and benzothiazole analogue (V) which can be further derivatized by alkylation reactions.

Reinterpretation of the Brønsted α for Redox Reactions Based on the Effect of Substituents on Hydride Transfer Reaction Rates between NAD+ Analogues

Rate and equilibrium constants have been determined spectrophotometrically for two sets of hydride transfer redox reactions between acridine and benzothiazoline derivatives and between pyridine and benzimidazoline derivatives that can be regarded as NAD+/NADH analogues. According to generally accepted ideas of the relation between equilibrium constants, K, and rate constants, k, these reactions would all have Brønsted alpha values close to 0.5 since the equilibrium constants, K, for these reactions range from 10(-1) to 10(2). However, when the structural variation is in the hydride acceptor, the Brønsted alpha is less than 0.5 (0.38 and 0.42, respectively), and when the structural variation is in the hydride donor, the Brønsted alpha is greater than 0.5 (0.63 and 0.61, respectively) for the present systems. The Marcus theory of atom and group transfer can explain the difference of alpha values in terms of the tightness factor in the critical configuration. When the transition state is loose and symmetrical, the deviation of the Brønsted alpha from 0.5 can be obtained by adding or subtracting a tightness factor that depends on the location of the substituents.

Controlling parameters for radical cation fragmentation reactions: Origin of the intrinsic barrier

C—C bond cleavages of radical cations of 2-substituted benzothiazoline derivatives were investigated to determine the parameters controlling the fragmentation rate constants. In spite of the low oxidation potentials of the compounds, fragmentation rate constants greater than 1 × 106 s–1 could be achieved through weakening of the fragmenting bond by substituents that stabilize the radical fragment and exert steric crowding. A quantitative assessment of the relative roles of radical stabilization vs. steric effects to weaken the fragmenting C—C bond was achieved through DFT calculations. The calculated activation enthalpies matched reasonably well with the experimentally determined values. A thermokinetic analysis revealed that the fragmentations of benzothiazoline radical cations have relatively large intrinsic kinetic barriers, ascribed to the delocalized nature of the product radical and cation fragments. Interestingly, the same factors that lead to the large intrinsic barriers led, simultaneously, to large thermodynamic driving forces for the fragmentations, which should lead to lower activation barriers. These effects oppose each other kinetically and provide important insight into the design of fast radical ion fragmentation reactions.Key words: benzothiazoline, radical cation, fragmentation, steric effects, DFT.

Novel calcium antagonists. Synthesis and structure-activity relationship studies of benzothiazoline derivatives

A series of novel compounds having a benzothiazoline skeleton was studied for their structure-activity relationship (SAR) with respect to Ca2+ antagonistic activity. As test compounds, analogues of 3-acyl-2-arylbenzothiazolines (3) were synthesized. Benzothiazoline derivatives (3) exerted higher Ca2+ antagonistic activity than the corresponding thiazolidine derivatives (2). Effects of substituents R1-R4, the substitution position of the aminoalkoxy group and R2, and the length of the methylene chain on biological activities were examined. Compound 4 [3-acetyl-2-[5-methoxy-2-[4-[N-methyl-N-(3,4,5-trimethoxyphenethyl ) amino]butoxy]phenyl]benzothiazoline hydrochloride] showed a potent Ca2+ antagonistic activity in vitro and dual inhibition on the fast Na+ inward channel and the slow Ca2+ inward channel in Langendorff perfused rabbit hearts. Compound 4 also showed a long-acting hypotensive effect in spontaneously hypertensive rats and prevented acute pulmonary thrombotic death in mice.

ChemInform Abstract: Novel Reactions of Benzothiazoline Derivatives.

AbstractDie Umsetzung des Benzothiazols (I) mit dem Arin (II) führt zur Verbindung (III).

Novel Reactions of Benzothiazoline Derivatives

Novel Reactions of Benzothiazoline Derivatives

Synthesis of 2-substituted 5-arylidenethiazolin-4-ones from α,β-unsaturated acyl isothiocyanates

α,β-Unsaturated acyl isothiocyanates react with N-methylaniline to give thioureas which, when treated with bromine in chloroform, afford benzothiazoline derivatives. Under the same reaction conditions primary amines, diethylamine, piperidine and morpholine furnish 2-substituted 5-arylidenethiazolin-4-ones. Their structure was corroborated by an independent synthesis and on the basis of spectral (IR, 1H-NMR and mass) evidence.

Novel Reactions of Benzothiazoline Derivatives

Novel Reactions of Benzothiazoline Derivatives

Studies on benzothiazoline derivatives. IV. Synthesis and novel ring expansion reaction of benzothiazoline sulfoxides.

The oxidation of 3-acylbenzothiazolines (IV) with m-chloroperbenzoic acid gave 3-acylbenzothiazoline sulfoxides (V) and sulfone (VI) in high yield. The stereochemistry of the compounds V is discussed on the basis of nuclear magnetic resonance spectroscopic studies. Reaction of the compound V with refluxing acetic anhydride resulted in the formation of novel ring expansion products, 4-acylbenzothiazine derivatives. A mechanism involving the sulfenic anhydride as an intermediate is proposed for this ring expansion.

Studies on benzothiazoline derivatives. II. Syntheses of benzothiazoline derivatives possessing substituent groups at 2- and 3-positions (author's transl)

Studies on benzothiazoline derivatives. II. Syntheses of benzothiazoline derivatives possessing substituent groups at 2- and 3-positions (author's transl)

Benzothiazoline derivatives. II. Preparation of N‐substituted derivatives of 2‐benzothiazolinethione by thiation of the 2‐oxo analogs

AbstractThuiation of the benzoate and acetate esters of 3‐(2‐hydroxyethyl)‐2‐benzothiazolinone (Ig) gave the corresponding thiones. The benzoate was then deblocked to yield 3‐(2‐hydroxyethyl)‐2‐benzothiazolinethione (Ik), a compound not accessible by direct addition or substitution. Attempts to introduce a chlorine (or bromine) atom in place of the hydroxy 1 group in the latter compound or its S‐isomer, 2‐(2‐hydroxyethylthio)benzothiazole (11a), gave 2,3‐dihydrothiazolo‐[2,3‐b ] benzothiazolium chloride (or bromide) (IIIa or b). The latter compound undergoes dihydrothiazolo ring opening when treated with sodium hydroxide or sodium sulfide to give bis[2‐(2‐benzolhiazolinon‐,3‐yl)ethyl]disulfide (IVc) or bis[2‐(2‐benzothiazolinethion‐3‐yl)ethyl] disulfide (lVb),respectively. 2‐Benzothiazolinethione reacted with ethylenimine and with N‐phenylethylenimine to give S‐substituted derivatives. Addition to vinyl n‐butyl ether gave the expected N‐substituted derivative, which was found to undergo removal of the butyoxyethyl group when subjected to conventional conditions for ether cleavage.

Benzothiazoline derivatives. I. Reaction of 2‐benzothiazolinethione with ethylene oxide

AbstractTreatment of 2‐benzothiazolinethione with excess ethylene oxide in acetic acid resulted in N‐hydroxyethylation and thiono‐oxo replacement to give 3‐(2‐hydroxyethyl)‐2‐benzothiazolinone. This product was also obtained when S‐alkylthiobenzothiazoles were treated in this way. Similar treatment of the N‐substituted compounds 3‐methyl‐2‐benzothiazolinethione and 3‐(2‐hydroxyethyl)‐2‐benzothiazolinethione gave simple thiono‐oxo replacement.