V. Kalcheva

Computational study of the general base catalysed aminolysis of 2-benzoxazolinone

B3LYP/6-31G* computations were applied in examining the possible mechanistic pathways for the reaction of ring opening of 2-benzoxazolinone by aminolysis with methylamine in the case of general base catalysis by a second molecule of the amine. Transition state structures and energies were determined for concerted and neutral stepwise pathways. The theoretical data show that the concerted mechanism is more favourable than the neutral stepwise pathway by 2.54 kcal/mol in the gas phase.

RING TRANSFORMATION OF 3-(2-OXOPROPYL)-2(3H)-BENZOTHIAZOLONE IN REACTION WITH PRIMARY AMINE

Abstract New 3-alkyl-1,3-dihydro-1-(2-mercaptophenyl)-4-methyl-2H-imidazolin-2-ones and the products of their oxidation-the corresponding disulfides are synthesized by ring transformation of 3-(2-oxopropyl)-2(3H)-benzothiazolone in reaction with primary amines. The supposed reaction mechanism is disscused. This reaction is a suitable one-stage method for the synthesis of 3,4-substituted 2H-imidazolones containing a 2-mercaptophenyl group.

Synthesis of Benzo[b]imidazo[1,5-d][1,5]-thiazepines. Derivatives of a Novel Ring System

Abstract Derivatives of a novel tricyclic system having a 1,5-benzothiazepine skeleton are described. A method for synthesis of the title compounds 5, consisted of an intramolecular cyclization of 1-(2-carboxymethylthiophenyl)-2H-imidazol-2-ones 4 in PPA, is presented. Compounds 4 were prepared by a reaction of 1-(2-mercaptophenyl)-2H-imidazol-2-ones 3 with chloroacetic acid. 2H-Imidazolones 3 were obtained by a ring transformation of substituted 2(3H)-benzothiazolones 2 in reactions with primary amines. The method is convenient because of its simplicity and good yields.

Molecular Mass Characteristics of (2-Benzothiazolon-3-yl)acetic Acid–Telechelic Poly(ethylene oxide)s Determined by MALDI-TOF Mass Spectrometry and SEC

(2-benzothiazolon-3-yl)acetic acid-telechelic poly(ethylene oxides)s (1100-4440 Da) with narrow molecular mass distributions (MMD) were analysed by matrix-assisted laser desorption-ionisation time-of-flight mass spectrometry (MALDI-TOF MS) and size exclusion chromatography (SEC). The average molecular masses (M n and M w ) determined by both methods were compared and a good agreement established. The cutting of the low molecular part of the initial poly(ethylene glycol) MMD during purification and isolation of the produced telechelic poly(ethylene oxide)s was proved. For this reason, the degree of esterification (x) of poly(ethylene glycol) (PEG) with (2-benzothiazolon-3-yl)acetic acid was calculated by MALDI-TOF MS and SEC, using additional UV data. The two series of x values derived from the M n -values, determined by the two methods, are very close. All of them are less than unity and the differences between the two types of x values decrease with the PEG molecular mass growth.

Synthesis of N-substituted 2-benzoxalones

Abstract3-Acetylaminomethyl-2-benzoxazolones are obtained by Beckmann rearrangement of the anti-oximes of 3-acetonyl-2-benzoxazolones. The isomeric 3-(N-methylcarbamoylmethyl)-2-benzoxazolones are synthesized by alkylation of 2-benzoxazolone with chloroacetic acid, followed by reaction of the 3-carboxymethyl-2-benzoxazolones obtained with thionyl chloride and methylamine.

Recyclization of 4,5-diphenyloxazolin-2-one and -2-thione under the influence of amines

Abstract4,5-Diphenyl-4-oxazolin-2-one and -2-thione undergo recyclization to 1-substituted 4,5-diphenyl-4-imidazolin-2-ones and -2-thiones, respectively, under the influence of primary amines. The action of hydrazine hydrate on the oxazolone leads to 5,6-diphenyl-1,2,3,4-tetrahydro-1,2,4-triazin-3-one. The corresponding ureas were isolated from the reaction mixtures in a number of cases.

2-Aminooxazoles and their derivatives (review)

The literature data on methods for the synthesis of 2-aminooxazoles and their benzo derivatives and their physicochemical properties and transformations are correlated.

AN EFFICIENT APPROACH TO THE IMIDAZO[5,1-c][1,4]BENZOTHIAZINE SKELETON. A NOVEL TRICYCLIC RING SYSTEM

Derivatives of a new type tricyclic system having a 1,4-benzothiazine skeleton are described. The reaction of l-(2-mercaptophenyl)-2//-imidazol-2-ones 2 with excess formaldehyde in acid medium resulted in the formation of 2,4-dihydro-lH-imidazo[5,l-c][l,4]benzothiazin-l-one 3. The starting compounds 2 were prepared by a modification of a previously described method of ring transformation of 3-(2-oxopropyI)-2(3//)-benzothiazoIones in reactions with primary amines.

Ring Transformations of 2-(2-Oxopropyl-, 2-oxo-2-phenylethylthio) Oxazolo[4,5-b]pyridine in the Reaction with N-containing Nucleophiles

Abstract 2,3-Dihydro-2-(3-hydroxy-2-piridylimino)-thiazoles 7, 9a-f and 11 are synthesized by ring transformation of 2-(2-oxo-propylthio)oxazolo[4,5-b] pyridine (2) and 2-(2-oxo-2-phenylethylthio) oxazolo-[4,5-b]pyridine (3) in reactions with amines, hydrazine or ammonium acetate.

Synthesis of semicarbazones and thiosemicarbazones of 1-(2-benzothiazolon-3-yl) propanones

Semi- and thiosemicarbazones were synthesized by the reaction of 1-(2-benzothiazolon-3-yl)propanones with semi- and thiosemicarbazide. These compounds are more active in stimulating plant growth than the starting propanones.