Reaktionen von 3-(Dimethylamino)-2H-azirinen mit 1,3-Benzoxazol-2(3H)-thion

Reaction of 3-(Dimethylamino)-2H-azirines with 1,3-Benzoxazole-2(3H)-thione The reaction of 3-(dimethylamino)-2H-azirines 2 with 1,3-benzoxazole-2(3H)-thione ( 5 ), which can be considered as NH-acidic heterocycle (pK_aca. 7.3), in MeCN at room temperature, leads to 3-(2-hydroxyphenyl)-2-thiohydantoins 6 and thiourea derivatives of type 7 (Scheme 2). A reaction mechanism for the formation of the products via the crucial zwitterionic intermediate A ′ is suggested. This intermediate was trapped by methylation with Mel and hydrolysis to give 9 (Scheme 4). Under normal reaction conditions, A ′ undergoes a ring opening to B which is hydrolyzed during workup to yield 6 or rearranges to give the thiourea 7. A reasonable intermediate of the latter transformation is the isothiocyanate E (Scheme 3) which also could be trapped by morpholine. In i-PrOH at 55–65° 2a and 5 react to yield a mixture of 6a , 2-(isopropylthio)-1,3-benzoxazole ( 12 ), and the thioamide 13 (Scheme 5). A mechanism for the surprising alkylation of 5 via the intermediate 2-amino-2-alkoxyaziridine F is proposed. Again via an aziridine, e.g. H ( Scheme 6 ), the formation of 13 can be explained.     

(Fluorosilyl)ethylenediamines and fluorosilyl-1,3-diaza-2-silacyclopentanes

This paper presents the chemistry of ethylenediamines and fluorosilanes. The synthesis of thermally stable monosilyl (1-5)- and bis(fluorosilyl)ethylenediamines (6) is described. Starting with the dilithium salt of ethylenediamine and F₂Si(CMe₃)₂ the five-membered 1,3-diaza-2-silacyclopentane (8) is obtained. The reaction of tetra- and trifluorosilanes with dilithiated bis(silyl)ethylenediamines leads to the formation of 1,3-diaza-2-fluorosilylsilacyclopentanes (9-14). Fluorosilanes substitute 8 in 1 and 3 positions (15-28). A fluorosilyl-bridged five-membered ring (29) is isolated in the reaction of 1-trimethylsilyl-1,3-diaza-2-silacyclopentane, BuLi and MeSiF₃. In the synthesis of N-fluorosilyl-1,3-diaza-2-silacyclopentanes constitutional isomers were formed (30-33). Quantum-chemical calculations support the isomerisation mechanism. An iminosilane with an SiN double bond is the intermediate product of the rearrangement process.Crystal structures of 7, 13, 20 and 23 are reported.     

Syntheses and coordination behaviour of 2-(ortho-phosphinophenyl)-functionalised 1,3-dioxolanes and 1,3-dioxanes towards a [(COD)Rh]-complex fragment - models for immobilised complexes

The syntheses are reported of the ether-phosphine ligands: 2-(ortho-diphenylphosphinophenyl)-1,3-dioxolane (1a), 2-(ortho-diisopropylphosphinophenyl)-1,3-dioxolane (1b), 2-(ortho-diphenylphosphinophenyl)-1,3-dioxane (1c), 2-(ortho-diisopropylphosphinophenyl)-1,3-dioxane (1d). Their reaction with [(COD)RhCl]₂ (COD: 1,5-cyclooctadiene) results in the formation of the mononuclear complexes: {chloro(COD)[2-(ortho-diphenylphosphinophenyl)-1,3-dioxolane]rhodium(I)} (2a), {chloro(COD)[2-(ortho-diisopropylphosphinophenyl)-1,3-dioxolane]rhodium(I)} (2b), {chloro(COD)[2-(ortho-diphenylphosphinophenyl)-1,3-dioxane]rhodium(I)} (2c), and {chloro(COD)[2-(ortho-diisopropylphosphinophenyl)-1,3-dioxane]rhodium(I)} (2d). The chloride ligands of compounds 2a and 2b were abstracted with TlPF₆, with accompanied insertion of an acetal oxygen atom of the ligands 1a and 1b into the coordination sphere of the metal centre, producing {(COD)[η²-P,O-2-(ortho-diphenylphosphinophenyl)-1,3-dioxolane]rhodium(I)}PF₆ (3a∗PF₆) and {(COD)[η²-P,O-2-(ortho-diisopropylphosphinophenyl)-1,3-dioxolane]rhodium(I)}PF₆ (3b∗PF₆). In contrast the dioxane analogues of 3, 3c∗BF₄ and 3d∗BF₄, were formed by reacting the ligands 1c, 1d with [Rh(COD)₂]BF₄. The ligands 1 and the complexes 2 serve as model compounds for their via acetalation to a polyvinylalcohol resin bound analogues. The complexes synthesised were employed as pre-catalysts in the hydroformylation reaction of 1-octene.     

Reaction of 5,5-diphenyl-2-thiohydantoin with 1,3-dibromopropane : Crystal and molecular structure of 2,3,4,5-tetrahydro-6,6-diphenylimidazo [2, 1-b]-thiazine-7 (6H)-one

The reaction between the potassium salt of 5,5-diphenyl-2-thiohydantoin (1) and 1,3-dibromopropane carried out in DME under anhydrous conditions has been found to give two isomeric diphenylimidazothiazines 2 and 3. When the reaction of 1 with 1,3-dibromopropane was performed in protic solvents (EtOH, HOH, NaOH) 2 and 3-(3-mercaptopropyl) - 5,5 - diphenylthiohydantoin (4) were formed. The latter is the product of hydrolysis of 3 taking place under the reaction conditions. 2,3,4,5 - Tetrahydro - 6,6 - diphenylimidazo [2,1-b] - thiazine - 7 (6H) - one (2) crystallises in space group P2₁/n with a =10.812(3), b =14.905(7), c =9.885(4) Å, β = 104.91(2)°. The 5-membered ring in 2 is planar whereas the 6-membered thiazine ring adopts the sofa conformation.     

1,3-Dilithio-2-(diphenylmethylene)propane

The reaction of 2,2-diphenylmethylenecyclopropane (5) with an excess of lithium and a catalytic amount of DTBB (4 mol %) in THF at −78 °C leads to the formation of dilithiated species 6-8 by reductive opening of the cyclopropane ring. Further reaction of these intermediates with different electrophiles [E = H₂O, D₂O, CH₂CMeCH₂Cl, Me₃SiCl, Me₃SiCH₂Cl, t-BuCHO, Me₂CO, Et₂CO, n-Pr₂CO, i-Pr₂CO, t-Bu₂CO, (CH₂)₅CO, Ph₂CO and adamantanone] is highly regioselective, yielding exclusively the corresponding products 9, after hydrolysis with water. However, when 3-chloro-2-(chloromethyl)propene (14) is used as a dielectrophile, the cyclisation to give a six-membered ring takes place through intermediate 6, giving compound 16 as the only reaction product.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

A convenient one-pot synthesis of 2-(trifluoromethyl)-3,4,7,8-tetrahydro-2H-chromen-5(6H)-one derivatives and their further transformations

The trifluoromethyl containing heterocycles, 2-hydroxy-4-aryl-3-(thien-2-oyl)-2-(trifluoromethyl)-3,4,7,8-tetrahydro-2H-chromen-5(6H)-one derivatives 4, were synthesized via a one-pot three-component reaction of aldehyde 1 with 1,3-cyclohexanedione 2 and 4,4,4-trifluoro-1-(thien-2-yl)butane-1,3-dione 3 in the presence of a catalytic amount of Et₃N. The effect of bases and solvents on the reaction efficiency and yield was briefly investigated. Treatment of 4 with an excess amount of NH₄OAc in ethanol afforded 2-trifluoromethyl-1H-quinolin-5-one derivatives 5. Refluxing of 4 with TsOH in CHCl₃ gave the corresponding dehydrated products 8.     

New copper(II) coordination compounds with 1,3-bis(5-(pyridin-2-yl)-1,2,4-triazol-3-yl)propane

Two new copper(II) complexes with 1,3-bis(5-(pyridin-2-yl)-1,2,4-triazol-3-yl)propane (H₂L), [Cu₂(HL)Cl₃] · H₂O (I) and [Cu(H₂L)](ClO₄)₂ (II), were described. The compounds were characterized by elemental analysis, IR spectroscopy, and magnetochemical data. According to X-ray diffraction data (CIF files CCDC nos. 1497511 (I), 1497512 (II)), complex I is binuclear and the metal cations are bound by the nitrogen atoms of the triazole ring and by the chloride anion. Complex II is mononuclear. Analysis of the temperature dependence of the magnetic susceptibility of I attests to the antiferromagnetic coupling of paramagnetic centers (–2J = 18 cm^–1). Exchange channels are analyzed by means of density functional theory (B3LYP/6-311G(d)) using the broken symmetry approach.     

Preparation of a chiral synthon for an HBV inhibitor: enzymatic asymmetric hydrolysis of (1α,2β,3α)-2-(benzyloxymethyl)cyclopent-4-ene-1,3-diol diacetate and enzymatic asymmetric acetylation of (1α,2β,3α)-2-(benzyloxymethyl)cyclopent-4-ene-1,3-diol

Enantioselective asymmetric hydrolysis of (1α,2β,3α)-2-(benzyloxymethyl)-cyclopent-4-ene-1,3-diol diacetate 1 to the corresponding (+)-monoacetate 2 was carried out using lipase PS-30 from Pseudomonas cepacia or pancreatin. A reaction yield of 85 M % with an enantiomeric excess (ee) of 98% was obtained. Using pancreatin, a reaction yield of 75 M % with an ee of 98.5% was obtained. Asymmetric acetylation of (1α,2β,3α)-2-(benzyloxymethyl)-cyclopent-4-ene-1,3-diol 3 to the corresponding (−)-monoacetate 4 was carried out using lipase PS-30 with isopropenyl acetate as the acylating agent. A reaction yield of 80 M % with an ee of 98% was obtained for (−)-monoacetate 4.     

Novel intramolecular cyclization of 2-(buta-1,3-dienyl)-3-methylpyrazines and 3-(buta-1,3-dienyl)-4-methyl-1,2,5-oxadiazoles into 5H-cycloheptapyrazines and 4H-cyclohepta-1,2,5-oxadiazoles

2-(Buta-1,3-dienyl)-3-methylpyrazines (5) and 3-(buta-1,3-dienyl)-4-methyl-1,2,5-oxadiazoles (10) were synthesized starting from base-induced reaction of 2,3-dimethylpyrazine or 3,4-dimethyl-1,2,5-oxadiazole with α,β-unsaturated carbonyls. The thus obtained heteroaromatics bearing a butadienyl moiety and a methyl at the adjacent position underwent intramolecular cyclization by the action of LDA to give the corresponding heteroaromatics fused with a seven-membered ring [7 (8)] and [11 (12)] in moderate to high yields.     

A facile stereoselective synthesis of difunctionalized 1,3-dienes containing tin and halogen via hydrozirconation of (Z)-3-(tributylstannyl)alk-3-en-1-ynes

Sonogashira coupling of (E)-α-iodovinylstannanes 1 with (trimethylsilyl)acetylene gave (Z)-1-(trimethylsilyl)-3-(tributylstannyl)alk-3-en-1-ynes 2, which underwent a desilylation reaction to afford (Z)-3-(tributylstannyl)alk-3-en-1-ynes 3 in high yields. (1E,3Z)-1-Halo-3-(tributylstannyl)-substituted 1,3-dienes 5 could be synthesized stereoselectively via hydrozirconation of (Z)-3-(tributylstannyl)alk-3-en-1-ynes 3, followed by trapping with iodine or NBS.     

Peculiarities of the reaction of (SPY-5-34)-dichloro-(κ2(C,O)-2-formylbenzylidene)(1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene)ruthenium with potassium hydridotris(pyrazolyl)borate

The reaction of (SPY-5-34)-dichloro-(κ²(C,O)-2-formylbenzylidene)(H₂IMes)ruthenium (H₂IMes=1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene) with potassium hydridotris(pyrazolyl)borate (KTp) in dichloromethane yielded an unusual ruthenium complex chloro(κ³(N,N,N)-chlorotris(pyrazolyl)borate)(κ²(C,C)-1-(2,4,6-trimethylphenyl)-3-(4,6-dimethylphenyl-2-methylidene)-4,5-dihydroimidazol-2-ylidene)ruthenium (2). In 2, a chlorotris(pyrazolyl)borate ligand, which had been created during this reaction, binds in κ³(N,N,N)-mode to the central ruthenium atom. Additionally, a double C–H activation of a methyl group of the H₂IMes resulted in the formation of a chelating N-heterocyclic biscarbene ligand and liberation of the former 2-formylbenzylidene as 2-methylbenzaldehyde. Formally, a double hydrogen transfer from a methyl group of the H₂IMes to the initial carbene carbon occurred. 2 was characterized by NMR spectroscopy, elemental analysis and single crystal X-ray structure determination. The reaction of KTp with (SPY-5-34)-dichloro(κ²(C,O)-2-ethoxycarbonylbenzylidene)(H₂IMes)ruthenium, on the other hand, gave the expected product chloro(κ³(N,N,N)-hydridotris(pyrazolyl)borate)(H₂IMes)(2-ethoxycarbonylbenzylidene)ruthenium (6). Compound 6 was characterized by NMR spectroscopy, elemental analysis and single crystal X-ray structure determination. Investigations of the relative activities of these complexes in model ring opening metathesis polymerizations showed a pronounced thermal latency. Polymerizations proceeded at temperatures above 100 °C in case of 6 and 130 °C in case of 2.     

Microbial reduction of 2-(6-m-methoxyphenyl-3-oxohexyl)-2,4-dimethylcyclopenta-1,3-dione with Schizosaccharomyces pombe (NRRL Y-164)

A mixture of cis- and trans-2-(6-m-methoxyphenyl-3-oxohexyl)-2,4-dimethylcyclopenta-1,3-dione (±)-10 was synthesized and incubated with Schizosaccharomyces pombe (NRRL Y-164) to give (+)-11, (+)-12, (−)-13, and (−)-14 in 19, 13, 22, and 16% yields, respectively. Chromic acid oxidation of these microbiologically reduced products gave (−)-10a, (+)-10b, (+)-10a, and (−)-10b, respectively.     

Polymerization of phenylacetylene by novel Rh (I)-, Ir (I)- and Ru (IV) 1,3-R2-3,4,5,6-tetrahydropyrimidin-2-ylidenes (R = mesityl, 2-propyl): Influence of structure on activity and polymer structure

The preparation of novel Rh (I) and Ir (I) complexes, i.e. [Rh(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD)]⁺[PF₆]⁻ (1), Rh(CF₃SO₃)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD) (2) and Ir(CF₃CO₂)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD) (3) (COD = 1,5-cyclooctadiene), is described. Compounds 1 and 3 were structurally characterized by X-ray diffraction. In 1, the N-heterocyclic carbene acts as a bidentate ligand with the carbene coordinating to the Rh(I) center and an arene group acting as a homoazallyl ligand. The catalytic activity of complexes 1–3 in the polymerization of phenylacetylene was studied and compared to that of RhCl(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD) (4), Rh(CF₃COO)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD) (5), [Rh(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD)]⁺[BF₄]⁻ (6), IrCl(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD) (7), IrCl(1,3-diisopropyl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD) (8), IrBr(1,3-di-2-propylimidazolin-2-ylidene)(COD) (9), RuCl₂(PCy₃)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(CH–C₆H₅) (10), RuCl₂(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(CH-2-(2-PrO)-5-NO₂-C₆H₃) (11), Ru(CO₂CF₃)₂(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(CH-2-(2-PrO)-5-NO₂-C₆H₃) (12). Compounds 1–6 were active in the polymerization of phenylacetylene. cis-Poly(phenylacetylene) (PPA) was obtained with the rhodium-based catalysts 1, 2, 4–6, trans-PPA was obtained with the Ir-based catalysts 3 and 8. In addition, compounds 1 and 6 were found to produce highly stereoregular PPA with a cis-content of 100% in the presence of water. Finally, the Ru-based metathesis initiator 12 allowed for the synthesis of trans-PPA, representing the first example of a ruthenium complex being active in the polymerization of a terminal alkyne.     

Synthesis, structure, and photoisomerization of derivatives of 2-(2-quinolyl)-1,3-tropolones prepared by the condensation of 2-methylquinolines with 3,4,5,6-tetrachloro-1,2-benzoquinone

A series of novel derivatives of the 1,3-tropolone (β-tropolone) system—2-(2-quinolyl)-5,6,7-trichloro-1,3-tropolones and 2-(2-quinolyl)-4,5,6,7-tetrachloro-1,3-tropolones have been prepared by the acid-catalyzed reaction of 2-methylquinolines with 3,4,5,6-tetrachloro-1,2-benzoquinone. The molecular structures of two compounds, 2-(4-chloro-6,8-dimethyl-5-nitro-2-quinolyl)-5,6,7-trichloro-1,3-tropolone 8 and 2-(4-chloro-7,8-dimethyl-5-nitro-2-quinolyl)-4,5,6,7-tetrachloro-1,3-tropolone 9, have been determined using X-ray crystallography. According to the performed DFT B3LYP/6-311++G^∗∗ calculations the tautomeric (OH) and (NH) forms of β-tropolones 8 and 9 are nearly energy equivalent, the latter being more stabilized in polar media. Photolysis of 2-(2-quinolyl)-1,3-tropolones in heptane solution leads to the disrotatory electrocyclic rearrangement resulting in the formation of a mixture of E- and Z-isomers of 3-[2(1H)-quinolinylyden]-bicyclo[3.2.0]hept-6-en-2,4-dione derivatives.     

Microwave-assisted Hantzsch thiazole synthesis of N-phenyl-4-(6-phenylimidazo[2,1-b]thiazol-5-yl)thiazol-2-amines from the reaction of 2-chloro-1-(6-phenylimidazo[2,1-b]thiazol-5-yl)ethanones and thioureas

N-Phenyl-4-(6-phenylimidazo[2,1-b]thiazol-5-yl)thiazol-2-amines (6a-q) have been synthesized by the Hantzsch thiazole reaction of 2-chloro-1-(6-phenylimidazo[2,1-b]thiazol-5-yl)ethanones (4a-e) with suitably substituted thioureas using microwave heating. The ethanones (4a-e) were prepared by the reaction of 6-phenylimidazo[2,1-b]thiazoles (3a-e) with chloroacetylchloride in refluxing 1,4-dioxane whereas the thiazoles (3a-e) were synthesized by the reaction of 2-bromo-1-phenylethanones (2a-e) with thiazol-2-amine in refluxing acetone.     

The reaction of (N-isocyanimino)triphenylphosphorane with dialkyl acetylenedicarboxylates in the presence of 1,3-diphenyl-1,3-propanedione: a novel three-component reaction for the stereoselective synthesis of dialkyl (Z)-2-(5,7-diphenyl-1,3,4-oxadiazepin-2-yl)-2-butenedioates

Reactions of dialkyl acetylenedicarboxylates with (N-isocyanimino)triphenylphosphorane in the presence of 1,3-diphenyl-1,3-propanedione proceed smoothly at room temperature to afford dialkyl (Z)-2-(5,7-diphenyl-1,3,4-oxadiazepin-2-yl)-2-butenedioates in high yields. The stereochemistry of the final products were confirmed by single crystal X-ray structure determination. The reaction is completely stereoselective.     

Synthesis of 2-phenyl-1,3-di(4-pyridyl)naphthvalene by photoinduced reversible valence isomerization of 2-phenyl-1,3-di(4-pyridyl)naphthalene

2-Phenyl-1,3-di(4-pyridyl)naphthvalene 3a was synthesized by the photoinduced reversible valence isomerization of 2-phenyl-1,3-di(4-pyridyl)naphthalene 2a. Then, 3a was converted into 3-phenyl-1,2-di(4-pyridyl)naphthalene 4a and 2a simultaneously. The t_1/2 of 3a in DMSO-d₆ at 90 °C was 2 h, while that at 110 °C was approximately 10 min.     

Reaction of 2-bromomethyl-1,3-thiaselenole with thiourea: en route to the first representatives of 2-(organylsulfanyl)-2,3-dihydro-1,4-thiaselenines

The regioselective reaction of 2-bromomethyl-1,3-thiaselenole 1 with thiourea is accompanied by rearrangement, expanding the ring to afford the corresponding six-membered isothiuronium salt, 2-[amino(imino)methyl]sulfanyl-2,3-dihydro-1,4-thiaselenine hydrobromide 2, a synthon of the 2,3-dihydro-1,4-thiaselenin-2-ylthiolate anion. The latter was used for the synthesis of the first representatives of 2-(organylsulfanyl)-2,3-dihydro-1,4-thiaselenines 3a–g, bis(2,3-dihydro-1,4-thiaselenin-2-yl) disulfide 5 and 1,6-bis(2,3-dihydro-1,4-thiaselenin-2-ylsulfanyl)hexane 6.     

Preparation,molecular structures,and characteristic properties of (E)-1-(2-furyl)- and (E)-1-(2-thienyl)-2-(3-guaiazulenyl)ethylenes and (E)-1-(3-furyl)- and (E)-1-(3-thienyl)-2-(3-guaiazulenyl)ethylenes

Wittig reactions of 2-furaldehyde (20) [and thiophene-2-carbaldehyde (21)] with (3-guaiazulenylmethyl)triphenylphosphonium bromide (19) in ethanol containing NaOEt at 25 °C for 24 h under argon give (E)-1-(2-furyl)-2-(3-guaiazulenyl)ethylene (22E) and (E)-1-(2-thienyl)-2-(3-guaiazulenyl)ethylene (23E) in 53 and 36% yields. Similarly, Wittig reactions of 3-furaldehyde (29) [and thiophene-3-carbaldehyde (30)] with 19 under the same reaction conditions as for 20 and 21 afford (E)-1-(3-furyl)-2-(3-guaiazulenyl)ethylene (31E) and (E)-1-(3-thienyl)-2-(3-guaiazulenyl)ethylene (32E) in 32 and 46% yields. Molecular structures and characteristic properties as well as preparation of the title E (i.e., one of the geometrical isomers) forms, with a view to comparative study, are reported. Moreover, reactions of those conjugated π-electron systems with TCNE (=tetracyanoethylene) in benzene [and in DMF (=N,N-dimethylformamide)] at 25 °C for 24 h under argon yield unique products, possessing interesting molecular structures, respectively, whose characteristic properties and crystal structures are documented, also.