Facile Synthesis of 2H-1,4-Benzothiazin-3(4H)-ketoximes and 2H-1,4-Benzoselenazin-3(4H)-ketoximes Promoted by SmI2

Abstract

2H-1,4-Benzothiazin-3(4H)-ketoximes and 2H-1,4-benzoselenazin-3(4H)-ketoximes were synthesized by the reductive cyclization of bis(o-nitrophenyl) disulfides or diselenides with aromatic or aliphatic β-nitroethylenes using SmI₂ in moderate to good yields under mild conditions.     

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.     

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.     

SYNTHESIS AND REACTIONS OF HALO DERIVATIVES OF 4-ISOPROPYL-2H-1,4-THIAZIN-3-ONE

Abstract

Reaction of 4-isopropyl-2H-1,4-thiazin-3-one 1 (R [dbnd] i-Pr) with N-chloro- and N-bromosuccinimide occurred exclusively at the 6-position to give 6-chloro and 6-bromo derivatives of 1 (R [dbnd] i-Pr), respectively, in high yield, in sharp contrast to the 2-aroyloxylation by benzoyl peroxide or m-chloroperbenzoic acid reported earlier.² Reaction of 1 (R [dbnd] i-Pr) with methanesulfonyl chloride in the presence of aluminum chloride afforded an addition compound, 4-isopropyl-5,6-dichloro-1,4-tetrahydrothiazin-3-one. The 2-chloro derivative 6 of 1 (R [dbnd] i-Pr) was successfully prepared by hydrolysis of the 2-m-chloroben-zoyloxy derivative of 1 (R [dbnd] i-Pr) followed by treatment with thionyl chloride. Derivative 6 reacted readily under mild conditions with water, alcohols, thiols, ammonia and amines to give various 2-substituted compounds of 1 (R [dbnd] i-Pr). With phenol as a nucleophile, 1 (R [dbnd] i-Pr) reacted exclusively at the para position. Reaction at carbon atoms also occurred with N,N-dimethylaniline and 2,6-xylidine.     

SYNTHESIS OF 3-(2-MERCAPTO-4-THIAZOLYL)-2H-1-BENZOPYRAN-2-ONE AND ITS DERIVATIVES

Abstract

Treatment of 3-(2-bromoacetyl)coumarins with ammonium dithiocarbamate provides 3-2-mercapto-4-thiazolyl)-2H-1-benzopyran-2-one (11) but not 4-hydroxy-4-(3-coumaririnyl) thiazolidine-2-thione (I). II undergoes smooth condensation with alkyl, aralkyl, phenacyl and acid halides to give corresponding thioethers and thioesters (III) respectively. The structures of the newly synthesized compounds were established on the basis of spectral data (IR, PMR and MS).     

A New Synthetic Approach Towards the Synthesis of 2-(3-Aryl-2H-1,4-benzthiazin-2-yl)-3-aryl-2H-1,4-benzothiazines

Synthesis of 2-(3-Aryl-2H-1,4-benzthiazin-2-yl)-3-aryl-2H-1,4-benzothiazines (3 a-e) from 3-aryl-5(4H)-isoxazolones (1 a-e) and 2-aminothiophenol (2).     

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.     

The preparation of 2H-1,4-benzoxazin-3-(4H)-ones via palladium-catalyzed intramolecular C-O bond formation

Pd/PtBu(3)-catalyzed intramolecular C-O bond formation has been used to access aryl- and alkyl-substituted benzoxazinones.     

A CONVENIENT SYNTHESIS OF NEW PYRIDOTHIENOPYRIMIDIN-4 (3H) ONES AND PYRIDOTHIENOPYRIMIDIN-2, 4(1H, 3H) DIONES

New derivatives of 2-substituted pyrido[3′,2′:4,5]thieno[3,2-d]pyri-midin-4(3H) ones and 3-substituted pyrido[3′,2′:4,5]thieno[3,2-d]pyri-midin-2,4(1H,3H) diones have been prepared by base catalyzed cyclocondensation of ethyl-3-aminothieno[3,2-b]pyridine-2-carboxylate with aryl nitriles and aryl- or alkyl isocyanates respectively.     

Synthesis of 2-Benzylidene and 2-Hetarylmethyl Derivatives of 2H-1,4-Benzoxazin-3-(4H)-ones as Neuroprotecting Agents

A wide variety of the title compounds were synthesized by conventional and microwave methods in which the main step is a condensation of an aldehyde with a 1,4-benzoxazin-3-(4H)-one. In all cases, the Z diasteromers were the major products. Of particular importance is the synthesis of novel 2-(3,5-dibromo-4-hydroxy) and 2-(4-acetoxy-3,5-dibromobenzylidene derivatives of 2H-1,4-benzoxazin-3-(4H)-ones, four of which were shown in a previous publication to exhibit potent neuroprotecting properties. The yields of titled compounds ranged from 25 to 83%.     

Synthesis and properties of 3-cyano-4-(4-cyanophenyl)-1,4-dihydropyridine-2(3H)-thiones

Piperidinium 3-cyano-4-(4-cyanophenyl)-1,4-dihydropyridine-2(3H)-thiolates were obtained by the condensation of 1,3-dicarbonyl compounds, 4-cyanobenzaldehyde, and cyanothioacetamide in the presence of an equimolar amount of piperidine. The acidification of these thiolates gave the corresponding 1,4-dihydropyridine-2(3H)-thiones and pyridine-2(1H)-thione. Alkylation of 1,4-dihydropyridine-2-thiolates or the reaction mixture of the three-carbon condensation using iodacetamide gave 2-carbamoylmethylthio-1,4,5,6-tetrahydro- or 1,4-dihydropyridines, which were characterized by their conversion to 4,7-dihydrothieno[2,3-b]pyridines.Latvian Institute of Organic Synthesis, LV-1006, Riga, LatviaTranslated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 794–798, June, 2000.     

Synthesis of 2-(2-imidazolinyl) substituted 2,3-dihydro-4H-1,4-benzothiazine and 3,4-dihydro-2H-1,4-benzoxazines

An investigation into the synthesis of benzoxazine, benzoxathiane and benzothiazine derivatives of 2-(2-imidazolinyl)-1,4-benzodioxane has been carried out.     

3,3-二甲基-2-(4-取代苯乙烯基)-3H-吲哚氢溴酸盐的合成

2,3,3-三甲基-3H-吲(口朶)氢嗅酸盐与芳香醛反应的产物可作为3H-吲(口朶)系降花菁染料(norcyanine)。