Ring transformation of 5-aroyl-3(2H)-isothiazolones to 1,2,5-oxathiazole and 1,2,3-thiadiazole derivatives

Reaction of 2-substituted-5-aroyl-3(2H)-isothiazolones 2 with hydroxylamine and phenylhydrazine was found to give (N-substituted-carboxamido)methylene derivatives of 1,2,5-oxathiazole and 1,2,3-thiadiazole, 5 and 7 , respectively. The formation of these heterocycles was ascribed to a mononuclear heterocyclic rear-rangement of the initially formed ketone derivatives, oximes and hydrazones, through a nucleophilic attack of the = N-OH and = N-NH- groups on the S N bond of the isothiazolone ring. In a similar manner, reaction of isothiazolones 2 with hydrazine was found to give 4-aryl-5-(N-substituted-carboxamido)methyl-1,2,3-thiadiazoles 17 .     

A facile and novel synthesis of 1,6-naphthyridin-2(1H)-ones

A new and convenient procedure for the synthesis of 1,6-naphthyridin-2(1H)-ones and their derivatives is described. In the first scheme 5-acetyl-6-[2-(dimethylamino)ethenyl]-1,2-dihydro-2-oxo-3-pyridinecarbonitrile ( 4 ) obtained by the reaction of N,N-dimethylformamide dimethyl acetal with 5-acetyl-1,2-dihydro-6-methyl-2-oxo-3-pyridinecarbonitrile ( 3 ) was cyclized to 1,2-dihydro-5-methyl-2-oxo-1,6-naphthyridine-3-carbonitrile ( 5 ) by the action of ammonium acetate. Thermal decarboxylation of acid 7 obtained from the hydrolysis of nitrile 5 led to a mixture of 5-methyl-1,6-naphthyridin-2(1H)-one ( 8 ) and its dimer 9 . Hydrazide 11 obtained from nitrile 5 in two steps was converted to 3-amino-5-methyl-1,6-naphthyridin-2(1H)-one ( 12 ) by the Curtius rearrangement. The amino group of 12 was readily replaced by treatment with aqueous sodium hydroxide to yield 3-hydroxy-5-methyl-1,6-naphthyridin-2(1H)-one ( 13 ). In the second scheme, Michael reaction of enamines of type 20 with methyl propiolate, followed by ring closure gave 5-acyl(aroyl)-6-methyl-2(1H)-pyridinones ( 21 ) which in turn were treated with Bredereck's reagent to produce 5-acyl(aroyl)-6-[2-(dimethylamino)ethenyl]-2(1H)-pyridinones ( 22 ). Treatment of 22 with ammonium acetate led to the formation of 1,6-naphthyridin-2(1H)-ones 23 .     

Biomimetic synthesis of 4-acetylbenzoxazolin-2(3H)-one isolated from Zea mays

4-Acetylbenzoxazolin-2(3H)-one has been prepared biomimetically during attempts to synthesize the hemiacetalic hydroxamic acid 5-acetyl-2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one by the immediate degradation of this unstable compound generated as an intermediate. Thus, 4-acetylbenzoxazolin-2(3H)-one recently isolated from Zea mays kernels, and similar to other benzoxazolin-2(3H)-ones known from plant sources, is assumed to have originated from the degradation of natural 5-acetyl-2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one which in turn could have been enzymatically released by a β-glucosidase from the corresponding 2-β-D-glucoside.     

Synthesis and transformations of (±)-trans-4aβ(H), saα(H)-octahydro-4α,7β-dimethyl-2H-1-benzopyran-2-one

Hydrogenation of 4,7-dimethylcoumarin ( 1 ) in alkaline medium has been shown to furnish a mixture of (±)-trans-4aβ(H),8aα(H)-octahydro-4α,7β-dimethyl-2H-1-benzopyran-2-one ( 2 ), (±)-trans-4aβ(H),8aα(H)-octahydro-4α,7α-dimethyl-2H-1-benzopyran-2-one ( 3 ) and (±)-cis-4aα(H),8aα(H)-octahydro-4α,7α-dimethyl-2H-1-benzopyran-2-one ( 4 ) in 40:25:35:ratio, respectively. The stereochemistry of the major hydrogenation product 2 , has been established by transforming it to p-menthane derivatives e.g. (±)-2 (R)-[2′(R)hydroxy-4′(R) methylcyclohex-(1′S)-yl]propan-1-ol ( 20 ) and (±)-trans-3α,6β-dimethyl-3aβ(H),7aα(H)-octahydrobenzofuran ( 12 ). Starting from a mixture of lactones 2, 3 and 4 , lactone 3 has been obtained in pure state employing a sequence of reactions.     

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.     

Directed regiospecificity of 1,3-dipolar cycloaddition of 2-diazopropane to 4- and 5-substituted pyridazin-3(2H)-ones

6-Methoxy-2-methylpyridazin-3(2H)-one ( 1 ) gave with 2-diazopropane ( 8 ) a mixture of 3H-pyrazolo[3,4-d]-pyridazin-4(5H)-one derivative 12 , as the main product, and -7(6H)-one derivative 10 , as the minor product. On the other hand, 4-substituted pyridazin-3(2H)-ones 2, 3 , and 4 gave 3H-pyrazolo[3,4-d]pyridazin-7(6H)-one 10 , exclusively, while 5-substituted pyridazin-3(2H)-ones 5, 6 , and 7 produced only the isomeric 3H-pyrazolo[3,4-H]pyridazin-4(5H)-one 12 . The 5-phenylsulfonyl derivative 13 gave with 8 by elimination of a molecule of nitrogen, followed by rearrangement, 1,2-diazepine derivative 15 and with an excess of 8 3H-pyrazolo[3,4-d][1,2]diazepine derivative 16. 1 ,2-Dimethylpyridazine-3,6-(1H,2H)-dione and its derivatives 18 and 19 produced 3H-pyrazolo[3,4-d]pyridazine-4,7(5H,6H)-dione derivative 23 , while from 17 and 1-diazoindane ( 24 ) the spiro compound 27 was obtained. The 1,2-dihydro and 3a,7a-dihydro intermediates 21 and 25 were isolated.     

Eine überraschende Ringerweiterung von 3-(Dimethylamino)-2,2-dimethyl-2H-azirin zu 4,5-Dihydropyridin-2(3H)-on-Derivaten

An Unexpected Ring Enlargement of 3-(Dimethylamino)-2,2-dimethyl-2H-azirine to 4,5-Dihydropyridin-2(3H)-one Derivatives The reaction of 3-(dimethylamino)-2,2-dimethyl-2H-azirine ( 1a ) and 4,4-disubstituted 2-(trifluoromethyl)-1,3-oxazol-5(4H)-ones 7 in MeCN at 70° afforded 5-(dimethylamino)-3,6-dihydropyrazin-2(1H)-ones 10 (Scheme 4), whereas no reaction could be observed between 1a and 2-allyl-4-phenyl-2-(trifluoromethyl)-1,3-oxazol-5(2H)-one ( 8a ) or 4,4-dibenzyl-2-phenyl-1,3-oxazol-5(4H)-one ( 9 ). The formation of 10 is rationalized by a mechanism via nucleophilic attack of 1a onto 7 . The failure of a reaction with 9 shows that only activated 1,3-oxazol-5(4H)-ones bearing electron-withdrawing substituents do react as electrophiles with 1a . The amino-azirine 1a and 2,4-disubstituted 1,3-oxazol-5(4H)-ones 2b – e in refluxing MeCN undergo a novel ring enlargement to 4,5-dihydropyridin-2(3H)-ones 11 (Scheme 5). Several side products were observed in these reactions. Two different reaction mechanisms for the formation of 11 are proposed: either 1a undergoes a nucleophilic addition onto the open-chain ketene tautomer of 2 (Scheme 6), or 2 reacts as CH-acidic compound (Scheme 7).     

Chemistry of 5(2H)-isoxazolones: Novel conversion of positional isomers

Reactions of 4-arylidene-3-methyl-5(4H)-isoxazolones with nucleophiles lead to 4-substituted-benzyl-3-methyl-5(2H)-isoxazolones. Formation of 5(4H)- and 5(2H)-isoxazolone derivatives have been observed when 4-substituted-arylidene-3-rriethyl-5(4H)-isoxazolones are reacted with methyl magnesium iodide. Oxidation of 4-substituted-benzyl-3-methyl-5(2H)-isoxazolones with manganic acetate and pyridinium chlorochromate, gives 4,4′-bis[4-substituted-benzyl-3-methyl-5(4H)-isoxazolone]. Oxidation of 4-substituted-benzyl-3-methyl-5(2H)-isoxazolones with metachloroperbenzoic acid gives 4-hydroxy-4-substituted-benzyl-3-methyl-5(4H)-isoxazolones and reactions of the same substrates with N-bromosuccinimide furnish 4-bromo-4-substitutedbenzyl-3-methyl-5(4H)isoxazolones.     

One‐dimensional Cadmium(II) Coordination Polymers: Syntheses and Crystal Structures of [Cd(H2O)3(C5H6O4)]·2H2O,Cd(H2O)2(C6H8O4), and Cd(H2O)2(C8H12O4)

[Cd(H₂O)₃(C₅H₆O₄)]·2H₂O ( 1 ) and Cd(H₂O)₂(C₆H₈O₄) ( 2 ) were prepared from reactions of fresh CdCO₃ precipitate with aqueous solutions of glutaric acid and adipic acid, respectively, while Cd(H₂O)₂(C₈H₁₂O₄) ( 3 ) crystallized in a filtrate obtained from the hydrothermal reaction of CdCl₂·2.5H₂O, suberic acid and H₂O. Compound 1 consists of hydrogen bonded water molecules and linear {[Cd(H₂O)₃](C₅H₆O₄)_2/2} chains, which result from the pentagonal bipyramidally coordinated Cd atoms bridged by bis‐chelating glutarato ligands. In 2 and 3 , the six‐coordinate Cd atoms are bridged by bis‐chelating adipato and suberato ligands into zigzag chains according to {[Cd(H₂O)₃](C₅H₆O₄)_2/2} and {[Cd(H₂O)₂](C₈H₁₂O₄)_2/2}, respectively. The hydrogen bonds between water and the carboxylate oxygen atoms are responsible for the supramolecular assemblies of the zigzag chains into 3D networks. Crystallographic data: ( 1 ) P1¯ (no. 2), a = 8.012(1), b = 8.160(1), c = 8.939(1) Å, α = 82.29(1)°, β = 76.69(1)°, γ = 81.68(1)°, U = 559.6(1) ų, Z = 2; ( 2 ) C2/c (no. 15), a = 16.495(1), b = 5.578(1), c = 11.073(1) Å, β = 95.48(1)°, U = 1014.2(1) ų, Z = 4; ( 3 ) P2/c (no. 13), a = 9.407(2), b = 5.491(1), c = 11.317(2) Å, β = 95.93(3)°, U = 581.4(2) ų, Z = 2.     

Benzohydrazides,benzothiohydrazides, and benzamidrazones as sources of 1,3,4(2H)-oxadiazolenones, 1,3,4(2H)-thiadiazolenones,and 1,2,4(5H)-triazolenones

Benzohydrazides, benzothiohydrazides, and benzamidrazones have been converted to 1,3,4(2H)-oxadiazolenones, 1,3,4(2H)-thiadiazolenenones, and 1,2,4(5H)-triazolenones respectively by reaction with ethyl chloroformate, with ethyl thiolchloroformate, and with phenyl isocyanate. In some reactions, a carbamate or urea has been isolated as intermediate.     

Structural Diversity of Sheets in Rubidium Uranyl Oxoselenates: Synthesis and Crystal Structures of Rb2[(UO2)(SeO4)2(H2O)](H2O), Rb2[(UO2)2(SeO4)3(H2O)2](H2O)4, and Rb4[(UO2)3(SeO4)5(H2O)]

Single crystals of three rubidium uranyl selenates, Rb₂[(UO₂)(SeO₄)₂(H₂O)](H₂O) ( 1 ), Rb₂[(UO₂)₂(SeO₄)₃(H₂O)₂](H₂O)₄ ( 2 ), and Rb₄[(UO₂)₃(SeO₄)₅(H₂O)] ( 3 ), have been prepared by evaporation from aqueous solutions made out of mixtures of uranyl nitrate, selenic acid and Rb₂CO₃. The structures of all compounds have been solved by direct methods on the basis of X‐ray diffraction data sets. The crystallographic data are as follows: ( 1 ): orthorhombic, Pna2₁, a = 13.677(2), b = 11.8707(13), c = 7.6397(9) Å, V = 1240.4(3) ų, R₁ = 0.045 for 2396 independent observed reflections; ( 2 ): triclinic, P1¯, a = 8.4261(12), b = 11.8636(15), c = 13.3279(18) Å, α = 102.612(10), β = 107.250(10), γ = 102.510(10)°, V = 1183.7(3) ų, R₁ = 0.067 for 4762 independent observed reflections; ( 3 ): orthorhombic, Pbnm, a = 11.3761(14), b = 15.069(2), c = 19.2089(17) Å, V = 3292.9(7) ų, R₁ = 0.075 for 3808 independent observed reflections. The structures of the phases 1 , 2 , and 3 are based upon uranyl selenate hydrate sheets composed from corner‐sharing pentagonal [UO₇]^8— bipyramids and [SeO₄]^2— tetrahedra. In the crystal structure of 1 , the sheets have composition [(UO₂)(SeO₄)₂(H₂O)]^2— and run parallel to (001). The interlayer contains Rb⁺ cations and additional H₂O molecules. In structure of 2 , the [(UO₂)₂(SeO₄)₃(H₂O)₂]^2— sheets are oriented parallel to (101). Highly disordered Rb⁺ cations and H₂O molecules are located between the sheets. The structure of 3 is based upon [(UO₂)₃(SeO₄)₅(H₂O)]^4— sheets stacked parallel to (010) and contains Rb⁺ cations in the interlayers. The topologies of the uranyl oxoselenate sheets observed in the structures of 1 , 2 , and 3 are related to the same simple and highly‐symmetric graph consisting of 3‐connected white and 6‐connected black vertices.     

The preparation of 5-(2-aminophenyl)-1,3,4-oxadiazole-2(3H)-one and its rearrangement to 3-amino-2,4(1H,3H)-quinazolinedione

When anthranilic acid hydrazide is reacted with 1,1-carbonyldiimidazole inTHF 5-(2-aminophenyl)-1,3,4-oxadiazole-2(3H)-one (4) is formed. It can also be prepared from 1-o-aminobenzoyl-4,4-dimethylsemicarbazide which eliminates methylamine when boiled withDMF. On heating the 5-(2-aminophenyl)-1,3,4-oxiadiazole above its melting point it rearranges to 3-amino-2,4(1H,3H)-quinazolinedione (5).

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Die Darstellung von 5-(2-Aminophenyl)-1,3,4-oxadiazol-2(3H)-on und dessen Umlagerung in 3-Amino-2,4(1H,3H)-chinazolindion

Zusammenfassung Bei der Reaktion von Anthranilsäurehydrazid mit 1,1-Carbonyldiimidazol inTHF wird 5-(2-Aminophenyl)-1,3,4-oxadiazol-2(3H)-on (4) gebildet. Dieses kann auch aus 1-o-Aminobenzoyl-4,4-dimethylsemicarbazid dargestellt werden, welches beim Kochen mitDMF Methylamin eliminiert. Beim Erhitzen von 5-(2-Aminophenyl)-1,3,4-oxadiazol über seinen Schmelzpunkt tritt Umlagerung zu 3-Amino-2,4(1H,3H)-chinazolindion (5) ein.

     

Direct introduction of heterocyclic residues into 1,2,4-triazin-5(2H)ones

3-Aryl-1,2,4-triazin-5(2H)-ones 1a-c react with indoles 2a-c in trifluoroacetic acid/chloroform or in boiling butanol or acetic acid to give 3-aryl-6-(indolyl-3)-1,6-dihydro-1,2,4-triazin-5(2H)-ones 3a-g . Oxidation of the dihydro-1,2,4-triazin-5(2H)-ones 3a-e afforded 6-(indolyl-3)-1,2,4-triazin-5(2H)-ones 4a-e , products of nucleophilic substitution of hydrogen in 1a-c . Refluxing 1b with N-methylpyrrote 5b in butanol for an extended time resulted in the formation of 3-(4-chlorophenyl)-6-(1-meuiylpyrrolyl-2)-1,2,4-triazin-5(2H)-one 4h. The reaction of 1a-c with indoles 2a-c , pyrroles 5a,b , 1,3-dimethyl-2-phenylpyrazol-4-one (8) and aminothiazoles 9a,b in acetic anhydride affords the 1-acetyl-3-aryl-6-hetaryl-1,6-dihydro-1,2,4-triazin-5(2H)-ones 6a-s . Reaction of 1a-c with N-methyl-pyrrole 5b in acetic anhydride gives beside the 1:1 addition products 6h-k also the 2:1 addition products 7a-c .     

Pyrimido[4,5-e](1,2,4)-triazolo[3,4-b](1,3,4)-thiadiazine-7,9(6H8H)-diones

Some 5H-pyrimido[4,5-e](1,2,4)-triazolo[3,4-b](1,3,4)-thiadiazine-7,9-(6H,8H)-diones (4 a–d) have been synthesised by the condensation of 3-alkyl-4-amino-5-mercapto-(1,2,4)-triazoles (1 a–d) with 5-bromobarbituric acid (2a). Similarly some 9a-nitro-5H-pyrimido[4,5-e](1,2,4)-triazolo[3,4-b](1,3,4)-thiadiazine-7,9(8H,9aH)-diones (5 a–d) have been obtained by the condensation of1 a–d with 5-bromo-5-nitrobarbituric acid (2b) and final cyclisation withPPA. The structures have been confirmed by PMR spectra and analytical results.

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Pyrimido[4,5-e](1,2,4)-triazolo[3,4-b](1,3,4)-thiadiazin-7,9(6H,8H)-dione

Zusammenfassung Es wurden einige 5H-pyrimido[4,5-e](1,2,4)-triazolo[3,4-b](1,3,4)-thiadiazin-7,9(6H,8H)-dione (4 a–d) mittels Kondensation von 3-Alkyl-4-amino-5-mercapto-(1,2,4)-triazolen (1 a–d) mit 5-Brombarbitursäure (2 a) dargestellt. Des weiteren wurden einige 9a-Nitro-5H-pyrimido[4,5-e](1,2,4)-triazolo[3,4-b](1,3,4)-thiadiazin-7,9(8H,9aH)-dione (5 a–d) über die Kondensation von1 a–d mit 5-Brom-5-nitrobarbitursäure (2 b) und anschließender Cyclisierung mitPPA synthetisiert. Die angeführten Strukturen wurden mittels PMR-Spektren und analytischen Daten abgesichert.

     

Nucleoside und Nucleotide. Teil 15. Synthese von Desoxyribonucleosid-monophosphaten und -triphosphaten mit 2(1H)-Pyrimidinon, 2(1H)-Pyridinon und 4-Amino-2(1H)-pyridinon als Basen

Nucleosides and Nucleotide. Part 15. Synthesis of Deoxyribonucleoside Monophosphates and Triphosphates with 2(1H)-Pyrimidinone, 2(1H)-Pyridinone and 4-Amino-2(1H)-pyridinone as the Bases The phosphorylation of the modified nucleosides 1-(2′-deoxy-β-D -ribofuranosyl)-2(1 H)-pyrimidinone (M_d, 4 ), 4-amino-1-(2′-deoxy-β-D -ribofuranosyl)-2(1 H)-pyridinone (Z_d, 6 ) and the synthesis of 1–2′-deoxy-β-D -ribofuranosyl-2(1 H)-pyrimidinone-5′-O-triphosphate (pppM_d, 1 ), 1-(2′-deoxy-β-D ribofuranosyl)-2(1 H)-pyridinone-5′-O-triphosphate (pppII_d, 2 ), and 4-amino-1-(2′-deoxy-βD -ribofuranosyl)-2(1 H)-pyridinone-5′-O-triphosphate (pppZ_d, 3 ) are described. The nucleoside-5′-monophosphates pM_d (5) and pZ_d (7) were obtained by selective phosphorylation of M_d (4) and Z_d (6) , respectively, using phosphorylchloride in triethyl phosphate or in acetonitril. The reaction of pM_d (5) pII _d (8) or pZ_d (7) with morpholine in the presence of DCC led to the phosphoric amides 9, 10 and 11 , respectively, which were converted with tributylammonium pyrophosphate in dried dimethylsulfoxide to the nucleoside-5′triphosphates 1, 2 and 3 , respectively.     

Syntheses of(C_8H_8)Ln(C_9H_7)·(THF)_2(Ln=Pr,Nd)and crystal structure of(C_8H_8)Pr(C_9H_7)·(THF)_2

This paper reports two lanthanide complexes of formula (C_9H_7)Ln(C_8H_8)·(THF)_2 whereLn is Pr or Nd,C_9H_7 is indenyl,and C_8H_8 is cyclooctatetraene (COT).The complexes were preparedby the reaction of LnCl_3 with K(C_9H_7) and K_2(C_8H_8) in THF.(C_9H_7)Pr(C_8H_8)·(THF)_2 crystallizes inTHF at - 15℃ in the monoclinic space group P2_1:with unit cell dimensions a=8.446(0),b=10.083(2),c=13.407(3),β=105.48(1)°,V=1100.43(35)~3,Dc=1.52g/cm~3 and Z=2.The final R valueis 0.033,R_w value is 0.030,respectively.In (C_9H_7)Pr(C_8H_8)·(THF)_2 a five-membered ring centroid ofC_9H_7,the C_8H_8 ring centroid and the two oxygen atoms from the two THF molecules form a distortedtetrahedral geometry around the metal.     

1,6-Additionen an 3-Methyl-5-methyliden-2-(5H)-furanon-Derivate

1,6-Additions to 3-Methyl-5-methylidene-2(5H)-furanone Derivatives The anions of thiophenol, methyl malonate and malononitrile react with 3-methyl-5,6-dihydro-2 (4H)-benzofuranone ( 1c ) by the formation of the corresponding 1,6-addition products cis- 5c (63%), trans- 6 (42%) and trans- 7 (76%), respectively. Likewise, the reaction of 3-methyl-5-methylidene-2 (5H)-furanone ( 1b ) with thiophenol yields the 1,6-addition product 5b (66%), and with the sodium salt of methyl aceto-acetate the 1,6-addition product 8 (11%) and the dispiro-dilactone 9 (39%).     

New 2‐methylisothiazolones

New N,N'‐bis(alkoxycarbonyl)‐L‐cystine bis(methylamides) 4a, 4b and N,N'‐bis(benzyloxycarbonyl)‐L‐cystine bis(methylamide) 4c have been synthesized by mixed anhydride method from the essential amino acid L‐cystine 1 in good yield. These cystine bis(methylamides) 4a,b,c have been cyclized with sulfuryl chloride. New 2‐methyl‐4‐amino‐3‐isothiazolone and 5‐chloro‐2‐methyl‐4‐amino‐3‐isothiazolone hydrobromide salts 7, 8 have been obtained by deacylation of 2‐methyl‐4‐(benzyloxycarbonyl)amino‐3‐isothiazolone 5c and 5‐chloro‐2‐methyl‐4‐(benzyloxycarbonyl)amino‐3‐isothiazolone 6c with hydrogen bromide in acetic acid. The microbicidal effect of the new 2‐methy]‐3‐isothiazolones 5a,b,c; 6a,b,c; 7 and 8 compounds obtained by the above method has been investigated.     

Synthesis and Structural Characterization of Two Molybdenum~phosphate Cluster Compounds: (C_(14)N_(14)H_(63) )Na(H_2Mo_6P_4O_(31))_2·8H_2Oand(C_(14)N_(14)H_(63))Na(H_2Mo_6P_4O_(31) )_2·5H_2O

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Ringerweiterung von 1,2-Thiazol-3(2H)-on-1,1-dioxiden und 3-Amino-2H-azirinen zu 4H-1,2,5-Thiadiazocin-6-on-1,1-dioxiden

Ring Enlargement of 1,2-Thiazol-3(2H)-one-1,1-dioxides and 3-Amino-2H-azirines to 4H-1,2,5-Thiadiazocin-6-one-1,1-dioxides Reaction of 3-amino-2H-azirines 2 with the 1,1-dioxides 4 and 7 of 1,2-thiazol-3(2H)-ones and 1,2-thiazoli-din-3-ones, respectively, in i-PrOH at room temperature leads to 4H-1,2,5-thiadiazocin-6(5H)-one-1,1-dioxides 5 (Scheme 2, Table) and the corresponding 7,8-dihydro derivatives 8 (Scheme 4), respectively. The structure of some of the new 8-membered heterocycles as well as the structure of the minor by-product 6 (Scheme 3) have been established by X-ray crystallography (Chapt. 4). The proposed reaction mechanism for the ring expansion to 5 and 8 (Scheme 2) is in accordance with previously published results of reactions of 2 and NH-acidic heterocycles and is further supported by the results of the reaction of 4a and the (1-¹⁵N)-labelled aminoazirine 2a *.