1,4-Benzodioxin-2(3H)-one and some of its derivatives

The methods of synthesis of 1,4-benzodioxin-2(3H)-one have been reexamined. Frequently quoted in the literature the method of Ghosh has been found to give impure (2-hydroxyphenoxy)acetic acid rather than the lactone. Using various methods some simple derivatives of the title lactone substituted in the benzene ring have been prepared and characterized. The bromination of the lactone with NBS gives predominantly 7-bromo-1,4-benzodioxin-2(3H)-one under electrophilic conditions, while 6-bromo-1,4-benzodioxin-2(3H)-one is obtained as a major isomer under photolytic conditions.     

2-甲基-1,5-苯并硫氮杂的基态和激发态反应的研究III:2-甲基-1,5-苯并硫氮杂4-(5H)-酮与-4-甲基-1,5-苯并硫氮杂-2(3H)-酮间的互变异构

用化学反应和光谱分析证实了2-甲基(1,5)苯并硫氮杂环庚三烯-4(5H)-酮和4-甲基(1,5)苯并硫氮杂环庚三烯-2(3H)-酮是作为互变异构混合物存在的.     

Benzoxazol-2 (3H)-one and 1,3,4-oxadiazol-2(3H) -one derivatives from substituted enaminones and ketoenamines

Enaminones and ketoenamines bearing a hydrazine type substituent undergo side chain thermal cyclization, the former into benzoxazol-2 (3H)-one derivatives and the latter into 1, 3, 4-oxadiazol-2 (3H)-one derivatives. Factors affecting such reactions are discussed.     

3-碘-5-甲基-1,5-苯并硫氮杂(艹卓)-4(5H)-酮的合成

以2-甲基硫代苯胺为原料,通过酰化反应、碘环化反应合成了3-碘-5-甲基-1,5-苯并硫氮杂(艹卓)-4(5H)-酮,总收率86.3%,其结构经NMR,IR和MS表征.     

Synthesis of 2H-1,4-thiazin-3(4H)-one 1-oxide and 2H-1,4-thiazin-3-(4H)-one 1,1-dioxide,structural analogs of uracil

The synthesis of 1,4-thiazine 1-oxide and 1,1-dioxide analogs of the antibiotic emimycin is described. Reaction of methylthioglycolate with 1-bromo-2,2-diethoxyethane gave methyl (2,2-diethoxyethylthio)acetate ( 2 ). Treatment of 2 with methanolic ammonia followed by cyclization furnished 2H-1,4-thiazin-3(4H)-one ( 5 ). Oxidation of 5 with m-chloroperoxybenzoic acid converted it to 2H-1,4-thiazin-3(4H)-one 1-oxide ( 6 ). Oxidation of 2 with potassium permanganate, followed by treatment with methanolic ammonia, and cyclization gave 2H-1,4-thiazin-3(4H)-one 1,1-dioxide.     

New synthesis of 4,5-dihydro-1,2,4-triazin-3(2H)-one derivatives through cyclic transformation of 1,3,4-oxadiazol-2(3H)-one derivatives

Some 5-aryl(or benzyl)-2-oxo-1,3,4-oxadiazole-3(2H)-acetones or acetophenones 2 were easily prepared. These compounds reacted with hydrazine derivatives to give 4,5-dihydro-1,2,4-triazin-3(2H)-one derivatives 3 , 4 and 6 in good yields. With phenylhydrazine, the intermediate hydrazones 5 were obtained. Their conversion into triazinones necessitated the presence of sodium ethylate.     

Combined experimental and computational study on the energetics of 1,2-benzisothiazol-3(2H)-one and 1,4-benzothiazin-3(2H, 4H)-one

The present work reports an experimental and computational study of the energetics of 1,2-benzisothiazol-3(2H)-one and 1,4-benzothiazin-3(2H, 4H)-one. The standard (p° = 0.1 MPa) massic energy of combustion, at T = 298.15 K, of each compound was measured by rotating bomb combustion calorimetry, in oxygen that allowed the calculation of the respective standard molar enthalpy of formation, in the condensed phase, at T = 298.15 K. The standard molar enthalpies of sublimation, at T = 298.15 K, were measured by high-temperature Calvet microcalorimetry. From the combination of data obtained by both techniques we have calculated the standard molar enthalpies of formation, in the gaseous phase, at T = 298.15 K. In addition, computational calculations were carried using the density functional theory with the B3LYP functional and the 6-31G1 basis set and some correlations between structure and energetics were obtained for the keto and enol forms of both compounds. Using the G3(MP2)//B3LYP composite method and various appropriate reactions, the standard molar enthalpies of formation of 1,2-benzisothiazol-3(2H)-one and 1,4-benzothiazin-3(2H, 4H)-one, at T = 298.15 K, were computationally derived and compared with the experimental data. The aromaticity of 1,2-benzisothiazol-3(2H)-one, 1,4-benzothiazin-3(2H, 4H)-one and that of some related species was evaluated by analysis of nucleus independent chemical shifts (NICS).     

Absolute Conformation and Configuration of (2S, 3S)-3-Acetoxy-5-(dimethylaminoethyl)-2-(4-methoxyphenyl)-2,3-dihydro-1,5-benzothiazepin-4(5H)-one Chloride (Dilthiazem Hydrochloride)

Resolution of racemic cis-3-(2-aminophenylthio)-2-hydroxy-3-(4-methoxyphenyl) propionic acid ( 2 ) via the cinchonidine salt 3 , and brucine salt 4 , isolation of the calcium salts (+)- and (?)- 5 , as well as their cyclization to enantiomeric 1,5-benzothiazepines (+)- and (?)- 1 , are described. X-Ray single-crystal analysis reveals (2S, 3S) absolute configuration of (+)- 1 on the basis of tentative comparison of CD data with those for the 1,4-benzodiazepine derivative (+)- 8 of known absolute configuration.     

Syntheses for 2-hydroxy-2H-1,4-benzothiazin-3(4H)-one derivatives as thio analogues of natural hemiacetals

Reductive cyclizations of methyl 2-(2-nitrophenylthio)acetate 2 by means of electrochemistry or by catalytic hydrogenation have been used as key steps in the syntheses of the hemiacetals 2-hydroxy-2H-1,4-benzothiazin-3(4H)-one 10 and its 4-hydroxy derivative 9 representing thio analogues of allelo chemicals found in Gramineae and Acanthaceae. In contrast to its natural counterpart 2,4-dihydroxy-2H-1,4-benzoxa-zin-3(4H)-one hydroxamic acid 9 did not undergo degradation by extrusion of formic acid.     

Synthesis of 3-methylquinazolin-4(3H)-one derivatives

Oxidation of 3-methyl-2-sulfanylquinazolin-4(3H)-one with chlorine dioxide under different conditions gave 2,2??-disulfanediylbis[3-methylquinazolin-4(3H)-one], 3-methyl-4-oxo-3,4-dihydroquinazoline-2-sulfonic acid, 3-methylquinazoline-2,4(1H,3H)-dione, 6-chloro-3-methylquinazoline-2,4(1H,3H)-dione, and N,N-diethyl-3-methyl-4-oxo-3,4-dihydroquinazoline-2-sulfonamide.     

Reaction of indol-3(2H)-one derivatives with some active methylene compounds

The reaction of substituted (Z)- and (E)-2-arylmethylideneindolin-3(2H)-ones with malononitrile gave the Micheal addition products which could be cyclised to the corresponding pyrano[3,2-b]indole. Larger molecules such as cyanoacetic acid and ethyl cyanoacetate failed to react.     

Syntheses for 2-amino and 2-mercapto-2H-1,4-benzoxazin-3(4H)-one and 2H-1,4-benzothiazin-3(4H)-one as aza and thio analogues of the natural product blepharigenin

2-Amino-2H-1,4-benzoxazin-3(4H)-one 3 , 2-amino-2H-1,4-benzothiazin-3(4H)-one 4 , 2-mercapto-2H-1,4-benzoxazin-3(4H)-one 7 , and 2-mercapto-2H-1,4-benzothiazin-3(4H)-one 8 representing aza and thio analogues of the natural product's aglucone Blepharigenin (2-hydroxy-2H-1,4-benzoxazin-3(4H)-one) from Gramineae and Acantnaceae species have been synthesized for the first time from their 2-bromo precursors 1 and 2 . Attempts to similarly prepare the 4-hydroxy derivatives of 7 and 8 , which would represent new thio analogues of the naturally occurring cyclic hydroxamic acid, 2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one, have failed.     

Separation of enantiomers and diastereomers of 4-hydroxy-2H-1,4-benzoxazin-3(4H)-one derivatives by capillary electrophoresis

Summary A high performance capillary electrophoresis (HPCE) procedure for the enantioseparation of the methyl acetals3 and4 of the natural products DIBOA1 and DIMBOA2, respectively, has been developed using borate buffers (pH 9–10 range), cyclodextrins as chiral additives and addition of up to 20% methanol. A mixture of GDIBOA5 and GDIMBOA6 of natural origin was also clearly separated. HPCE proved to be superior to HPLC by the first separation of GDIBOA5 and three of its diastereomers resulting from a synthetic approach to this acetalglucoside.     

Synthesis and structure of 2-(nitromethylene)-2H-1,4-benzothiazin-3(4H)-one

A new representative of benzothiazines, (2Z)-2-(nitromethylene)-2H-1,4-benzothiazin-3(4H)-one, was synthesized, and its structure was studied. According to ¹H NMR, IR, and UV spectral and X-ray diffraction data, the molecules are planar highly conjugated structures that exist in crystal as centrosymmetric dimers; the latter form layers overlapping with each other and held together by strong π-π interaction between the carbonyl groups of neighboring layers.     

2-Chloro-3H-indol-3-one and its reactions with nucleophiles

The title compound reacts with N- and S-nucleophiles to form 3-substituted indol-2-ones, but with C-nucleo-philes to afford either these or the corresponding 2-substituted indol-3-ones. This dichotomy of behavior is documented and rationalized.