Über die Umlagerung von Benzo[b]-1, 4-thiazepinen und 1, 4-Thiazepinen

The rearrangement of differently substituted 1, 4-thiazepines under various reaction conditions has been investigated. 2-Phenyl-4-methylthio-benzo [b]-1, 4-thiazepine ( 3 ) and 2-phenyl-benzo [b]-1, 4-thiazepine-4 (5H)-thione ( 2 ) extrude sulfur under the catalytic influence of bases and rearrange into 2-methylthio-4-phenyl-quinoline ( 4 ) and 4-phenyl-thiocarbostyril ( 6 ) respectively. Under the same conditions, 2-phenyl-4-methylthio-2, 3-dihydro-benzo [b]-1, 4-thiazepine ( 11 ) rearranges to 2-styryl-benzothiazine ( 12 ), whereas the dioxide 18 shows no tendency to rearrange. 2,7-Diphenyl-hexahydro-1,4-thiazepine-5-one( 19 ) could be converted into 2-styryl-5-phenyl-2-thiazoline ( 20 ) by treatment with polyphosphoric acid. The possible mechanisms of these rearrangements are discussed.     

Über die Oxo‐cyclotetraphosphane (PBut)4O1–4

Contributions to the Chemistry of Phosphorus. 243 On the Oxocyclotetraphosphanes (PBu^t)₄O_1–4 Under suitable conditions, the reaction of tetra‐tert‐butylcyclotetraphosphane, (PBu^t)₄, with dry atmospheric oxygen gives rise to the corresponding monoxide (PBu^t)₄O ( 1 ) which has been isolated by column chromatography. The reaction with hydrogen peroxide furnishes a mixture of oxocyclotetraphosphanes (PBu^t)₄O_1–4 consisting of two constitutionally isomeric dioxides (PBu^t)₄O₂ ( 2 a , 2 b ), the trioxide (PBu^t)₄O₃ ( 3 ), and the tetraoxide (PBu^t)₄O₄ ( 4 ), in addition to 1 . According to the ³¹P NMR parameters the oxygen atoms are exclusively exocyclically bonded to the phosphorus four‐membered ring. Which of the P atoms are present as λ⁵‐phosphorus follows from the different low‐field shifts of the individual P nuclei compared with the starting compound. Accordingly, 1 is 1,2,3,4‐Tetra‐tert‐butyl‐1‐oxocyclotetraphosphane, 2 a and 2 b are 1,2,3,4‐Tetra‐tert‐butyl‐1,2‐dioxo‐ and ‐1,3‐dioxocyclotetraphosphane, respectively, 3 is 1,2,3,4‐Tetra‐tert‐butyl‐1,2,3‐trioxocyclotetraphosphane, and 4 is 1,2,3,4‐Tetra‐tert‐butyl‐1,2,3,4‐tetraoxocyclotetraphosphane. When the oxidation reaction proceeds a fission of the P₄ ring takes place.     

4-hydroxy-2-quinolones. 200*. Bromination of 1-<Emphasis Type="Italic">R</Emphasis>-4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxylic acid pyridinylmethylene hydrazides

The behavior of 1-R-4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxylic acid pyridinylmethylene- hydrazides under bromination conditions using molecular bromine has been studied. It has been found that the 1-N-allyl derivative is characteristically halocyclized to the corresponding oxazolo[3,2-a]-quinoline, whereas the 1-N-hexyl-substituted acylhydrazone is unexpectedly brominated in the azomethine fragment.     

The reactions of 4-dicyanomethylene-2-phenyl-4H-1-benzopyran and some benzologs with nucleophiles

4-Dicyanomethylene-2-phenyl-4H-1-benzopyran (1) reacts with primary amines under mild conditions to give 4-imino-3-alkyl-5-alkylimino-2-phenyl-3,4-dihydro-5H-[1]benzopyrano[3,4-c]-pyridine derivatives which, in turn, are hydrolyzed with acid to 4-imino-3-alkyl-2-phenyl-3,4-dihydro-5H-[1]benzopyrano[3,4-c]pyridin-5-ones. When more vigorous conditions are employed for the reactions of 1 with primary amines, Dimroth rearrangements take place and the products are derivatives of 4-alkyl- (or aryl)amino-5-alkyl- (or aryl)imino-2-phenyl-5H-[1]benzopyrano-[3,4-c]pyridine. The latter compounds are hydrolyzed by acid to the corresponding 5-pyridone derivatives. The reaction of 1 with piperidine gives 2-phenyl-4-piperidyl-5H-[1]benzopyrano-[3,4-c]pyridin-5-one. Sodium methoxide reacts with 1 to give 3-cyano-2-methoxy-4-(2-hydroxyphenyl)-6-phenylpyridine. Two benzologs of 1 have been allowed to react with primary and secondary amines and the products are analogous to those obtained from 1 .     

One-pot rapid synthesis of 4H-1-benzopyran derivatives in a deep eutectic solvent

A method for introducing a biologically active heterocycle, 2-methylquinoline into the 4-position of a 2-amino-4H-1-benzopyran skeleton is described. Choline chloride/glucose (1:1 molar ratio) was used as both the solvent and catalyst in the reaction of a salicylaldehyde, methylquinoline, and cyanoacetate to obtain 2-amino-4H-1-benzopyran derivatives in 48%–80% yields after short reaction times. The effects of the deep eutectic solvent type, substrate molar ratio, cosolvent, temperature, and reaction time were examined. The method has the advantages of simple steps, environmental friendliness, mild conditions, and wide substrate applicability. This is the first attempt to synthesize methylquinoline derivatives of 4H-1-benzopyran.     

Thermal degradation of poly(4-chloromethyl-α-acetoxystyrene) and poly(4-chloropropyl-α-acetoxystyrene)

The thermal degradation behaviour of two poly(4-ω-chloroalkyl-α-acetoxystyrene)s has been studied by means of dynamic and isothermal thermogravimetric analysis and gas chromatography-mass spectroscopy. The results show that two reactions occur during the first stage of the process. An elimination reaction gives acetic acid as major volatile species and a residue formed of para-substituted polyphenylacetylenes. A depolymerization reaction gives principally the para-substituted acetophenone corresponding to the starting monomer, and explains the low molecular weights of the residues. These two reactions are simultaneous in the case of poly(4-chloromethyl-α-acetoxystyrene), but are distinguishable in the case of poly(4-3-chloropropyl-α-acetoxystyrene). Kinetic parameters of the overall decomposition of these two polymers have been calculated and compared with those of poly(4-2-chloroethyl-α-acetoxystyrene).     

Copper‐catalyzed Synthesis of N‐alkylated 2‐(4‐substituted‐1H‐1,2,3‐triazol‐1‐yl)‐1H‐indole‐3‐carbaldehyde by Step‐wise and One‐pot Three‐component Huisgen's 1,3‐dipolar Cycloaddition Reaction

An efficient method for the synthesis of N‐alkylated 2‐(4‐substituted‐1H‐1,2,3‐triazol‐1‐yl)‐1H‐indole‐3‐carbaldehyde has been developed starting from oxindole and indole using Huisgen's 1,3‐dipolar cycloaddition reaction of organic azides to alkynes. The effect of catalysts and solvent on these reactions has been investigated. Among all these conditions, while using CuSO₄·5H₂O, DMF was found to be the best system for this reaction. It could also be prepared in a one‐pot three‐component manner by treating equimolar quantities of halides, azides, and alkynes. The Huisgen's 1,3‐dipolar cycloaddition reaction was performed using CuSO₄·5H₂O in DMF with easy work‐up procedure.     

A structural study of (1RS,2SR,3RS,4SR,5RS)‐2,4‐dibenzoyl‐1,3,5‐triphenylcyclohexan‐1‐ol chloroform hemisolvate and (1RS,2SR,3RS,4SR,5RS)‐2,4‐dibenzoyl‐1‐phenyl‐3,5‐bis(2‐methoxyphenyl)cyclohexan‐1‐ol

(1RS,2SR,3RS,4SR,5RS)‐2,4‐Dibenzoyl‐1,3,5‐triphenylcyclohexan‐1‐ol or (4‐hydroxy‐2,4,6‐triphenylcyclohexane‐1,3‐diyl)bis(phenylmethanone), C₃₈H₃₂O₃, (1), is formed as a by‐product in the NaOH‐catalyzed synthesis of 1,3,5‐triphenylpentane‐1,5‐dione from acetophenone and benzaldehyde. Single crystals of the chloroform hemisolvate, C₃₈H₃₂O₃·0.5CHCl₃, were grown from chloroform. The structure has triclinic (P) symmetry. One diastereomer [as a pair of (1RS,2SR,3RS,4SR,5RS)‐enantiomers] of (1) has been found in the crystal structure and confirmed by NMR studies. The dichoromethane hemisolvate has been reported previously [Zhang et al. (2007). Acta Cryst. E 63 , o4652]. (1RS,2SR,3RS,4SR,5RS)‐2,4‐Dibenzoyl‐3,5‐bis(2‐methoxyphenyl)‐1‐phenylcyclohexan‐1‐ol or [4‐hydroxy‐2,6‐bis(2‐methoxyphenyl)‐4‐phenylcyclohexane‐1,3‐diyl]bis(phenylmethanone), C₄₀H₃₆O₅, (2), is also formed as a by‐product, under the same conditions, from acetophenone and 2‐methoxybenzaldehyde. Crystals of (2) have been grown from chloroform. The structure has orthorhombic (Pca2₁) symmetry. A diastereomer of (2) possesses the same configuration as (1). In both structures, the cyclohexane ring adopts a chair conformation with all bulky groups (benzoyl, phenyl and 2‐methoxyphenyl) in equatorial positions. The molecules of (1) and (2) both display one intramolecular O—H...O hydrogen bond.     

Stereoselektive Synthese des Nitrit-reduzierenden Cofaktors Häm d1 ausgehend von Hämatoporphyrin

Steroselective Synthesis of the Nitrite-Reducing Cofactor Heme d₁ from Hematoporphyrin The nitrite-reducing cofactor heme d₁ has been synthesized in a few synthetic steps, starting from readily accessible hematoporphrin dimethyl ester (rac- 4a ). A single-crystal structure analysis of the synthesized target molecule rac- 10a unequivocally established the constitution and the relative configuration of heme d₁ ( 3 ).     

A two‐dimensional cadmium(II) coordination polymer constructed from 4‐carboxy‐1‐(4‐carboxylatobenzyl)‐2‐propyl‐1H‐imidazole‐5‐carboxylate and 1‐(4‐carboxylatobenzyl)‐2‐propyl‐1H‐imidazole‐4‐carboxylate ligands

Crystals of poly[[aqua[μ₃‐4‐carboxy‐1‐(4‐carboxylatobenzyl)‐2‐propyl‐1H‐imidazole‐5‐carboxylato‐κ⁵O¹O^1′:N³,O⁴:O⁵][μ₄‐1‐(4‐carboxylatobenzyl)‐2‐propyl‐1H‐imidazole‐4‐carboxylato‐κ⁷N³,O⁴:O⁴,O^4′:O¹,O^1′:O¹]cadmium(II)] monohydrate], {[Cd₂(C₁₅H₁₄N₂O₄)(C₁₆H₁₄N₂O₆)(H₂O)]·H₂O}_n or {[Cd₂(Hcpimda)(cpima)(H₂O)]·H₂O}_n, (I), were obtained from 1‐(4‐carboxybenzyl)‐2‐propyl‐1H‐imidazole‐4,5‐dicarboxylic acid (H₃cpimda) and cadmium(II) chloride under hydrothermal conditions. The structure indicates that in‐situ decarboxylation of H₃cpimda occurred during the synthesis process. The asymmetric unit consists of two Cd²⁺ centres, one 4‐carboxy‐1‐(4‐carboxylatobenzyl)‐2‐propyl‐1H‐imidazole‐5‐carboxylate (Hcpimda²⁻) anion, one 1‐(4‐carboxylatobenzyl)‐2‐propyl‐1H‐imidazole‐4‐carboxylate (cpima²⁻) anion, one coordinated water molecule and one lattice water molecule. One Cd²⁺ centre, i.e. Cd1, is hexacoordinated and displays a slightly distorted octahedral CdN₂O₄ geometry. The other Cd centre, i.e. Cd2, is coordinated by seven O atoms originating from one Hcpimda²⁻ ligand and three cpima²⁻ ligands. This Cd²⁺ centre can be described as having a distorted capped octahedral coordination geometry. Two carboxylate groups of the benzoate moieties of two cpima²⁻ ligands bridge between Cd2 centres to generate [Cd₂O₂] units, which are further linked by two cpima²⁻ ligands to produce one‐dimensional (1D) infinite chains based around large 26‐membered rings. Meanwhile, adjacent Cd1 centres are linked by Hcpimda²⁻ ligands to generate 1D zigzag chains. The two types of chains are linked through a μ₂‐η² bidentate bridging mode from an O atom of an imidazole carboxylate unit of cpima²⁻ to give a two‐dimensional (2D) coordination polymer. The simplified 2D net structure can be described as a 3,6‐coordinated net which has a (4³)₂(4⁶.6⁶.8³) topology. Furthermore, the FT–IR spectroscopic properties, photoluminescence properties, powder X‐ray diffraction (PXRD) pattern and thermogravimetric behaviour of the polymer have been investigated.     

A Reinvestigation of the α-Alkylation of 4-Monosubstituted 2-phenyloxazol-5(4H)-ones (‘azlactones’): A general entry into highly functionalized α,α-disubstituted α-amino acids

Novel, more reliable and general reaction conditions for the α-alkylation of 4-monosubstituted 2-phenyloxazol-5(4H)-ones ( = 4-monosubstituted 2-phenyl-azlactones) rac- 2 to 4,4-disubstituted 2-phenyloxazol-5(4H)-ones rac- 1 were found (Scheme 2). Thus, a whole range of highly functionalized rac- 1 were prepared in medium-to-good overall yields (40-90%, see Table). Azlactones rac- 1 are ideal precursors for the synthesis of optically pure α,α -disubstituted (R)- and (S)-α-amino acids.     

Photoinduzierte 1, 3-dipolare Cycloaddition von 3-Phenyl-2H-azirinen an Azodicarbonsäure-diäthylester. 32. Mitteilung über Photoreaktionen

Irradiation of 2, 2-dimethyl-3-phenyl- ( 1a ), 2, 3-diphenyl-2H-azirine ( 1b ) or the azirine-precursors 1-azido-1-phenyl-propene ( 2a ) and 1-azido-1-phenyl-ethylene ( 2b ), respectively, in benzene in the presence of azodicarboxylic acid diethylester, yields the corresponding 1, 2-carbethoxy-3-phenyl-Δ³-1, 2, 4-triazolines 4a–d (Scheme 1). Refluxing 4 ( a, c or d ) in 0, 2–0, 4M aqueous ethanolic potassium hydroxide leads to the formation of the 1-carbethoxy-3-phenyl-Δ²-1, 2, 4-triazolines 6 ( a, c or d ). Under the same conditions 4b is converted to 3, 5-diphenyl-1, 2, 4-triazole ( 7b , Scheme 2). In 10M aqueous potassium hydroxide solution heating of either 4 ( c or d ) or 6 ( c or d ) yields the 3-phenyl-1, 2, 4-triazoles 7 ( c or d ). Photolysis of 1-carbethoxy-5, 5-dimethyl-3-phenyl-Δ²-1, 2, 4-triazoline ( 6a ) in benzene in the presence of oxygen and trifluoroacetic acid methylester gives the 5-methoxy-2, 2-dimethyl-4-phenyl-5-trifluoromethyl-3-oxazoline ( 13 , Scheme 5). 5, 5-Dimethyl-3-phenyl-1, 2, 4-triazole seems to be the intermediate, which on losing nitrogen gives the benzonitrile-isopropylide ( 3a ).     

An efficient and regiospecific preparation of trifluoromethyl substituted 4‐( 1H‐pyrazol‐1 ‐yl)‐7‐chloroquinolines

A new series of 4‐[3‐alkyl(aryl)(heteroaryl)‐5‐hydroxy‐5‐trifluoromethyl‐4,5‐dihydro‐1H‐pyrazol‐1‐yl]‐7‐chloroquinolines, where [alkyl = CH₃; aryl = C₆H₅, 4‐CH₃C₆H₄, 4‐FC₆H₄, 4‐ClC₆H₄, 4‐BrC₆H₄, 4‐CH₃OCgH₄, 4‐NO₂CgH₄, 4‐biphenyl, 1‐naphthyl; heteroaryl = 2‐furyl and 2‐thienyl] has been regiospecifi‐caly obtained from the reaction of 7‐chloro‐4‐hydrazinoquinoline with 4‐substituted‐l,1,1‐trifluoro‐4‐methoxybut‐3‐en‐2‐ones in 61 ‐ 96 % yield. Subsequently, dehydration reaction of 4,5‐dihydropyra‐zolylquinolines under acid conditions furnished a new series of 4‐(3‐substituted‐5‐trifluoromethyl‐1H‐pyra‐zol‐1‐yl)‐7‐chloroquinolines in 73 ‐ 96 % yield.     

(±)‐2‐Aryl‐2,3‐dihydro‐4(1H)‐quinolinones by a tandem reduction–Michael addition reaction

An efficient synthesis of (±)‐2‐aryl‐2,3‐dihydro‐4(1H)‐quinolinones has been developed from chalcones prepared from 2′‐nitroacetophenone and a series of substituted benzaldehydes. The cyclization sequence is initiated by reduction of the nitro group under dissolving metal conditions using iron powder in concentrated hydrochloric acid. Milder conditions, using acetic acid or acetic acid–phosphoric acid as the reaction medium, were less satisfactory. Procedural details as well as a mechanistic discussion and reaction optimization studies are presented. J. Heterocyclic Chem., (2011).     

Substituted pyridopyrimidinones, 1: Convenient PTC alkylation and halogenation of 2‐hydroxy‐4H‐pyrido[1,2‐a]pyrimidin‐4‐one

Alkylation of 2‐hydroxy‐4H‐pyrido[1,2‐a]pyrimidin‐4‐one ( 1 ) was investigated under solid–liquid phase transfer catalysis conditions (PTC), using tetrabutylammonium bromide and potassium carbonate. The reaction with alkyl halides led to the formation of various 2‐alkoxy products, in fair yields. Reaction of compound 1 with epichlorohydrin and chloroacetonitrile, under the same PTC conditions, afforded novel O1,O3‐disubstituted glycerol and oxazolopyridopyrimidone betaine derivatives, respectively. Some 3‐halo‐, 3,3‐dihalo, and/or 2,3‐dihalopyrido[1,2‐a]pyrimidines were also prepared using different halogenating agents at different reaction conditions. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:19–27, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20245     

Synthesis of 2‐aryl‐1‐arylmethyl‐1H‐1,3‐benzimidazoles catalysed by ferric ammonium sulfate (NH4Fe(SO4)2) under solvent‐free conditions

NH₄Fe(SO₄)₂ was found to be a mild and effective catalyst for the selective synthesis of 2‐aryl‐1‐arylmethyl‐1H‐1,3‐benzimidazoles under solvent‐free conditions. Copyright © 2015 John Wiley & Sons, Ltd.     

Gold(I)‐Catalyzed Highly Diastereo‐ and Enantioselective Cyclization–[4+3] Annulation Cascades between 2‐(1‐Alkynyl)‐2‐alken‐1‐ones and Anthranils

This work reports gold‐catalyzed [4+3]‐annulations of 2‐(1‐alkynyl)‐2‐alken‐1‐ones with anthranils to yield epoxybenzoazepine products with excellent exo‐diastereoselectivity (dr>25:1). The utility of this new gold catalysis is manifested by applicable substrates over a broad scope. More importantly, the enantioselective versions of these [4+3]‐cycloadditions have been developed satisfactorily with chiral gold catalysts under ambient conditions (DCM, 0 °C); the ee levels range from 88.0–99.9 %. With DFT calculations, we postulate a stepwise pathway to rationalize the preferable exo‐stereoselection.     

Highly Enantioselective Synthesis of α‐Stereogenic Esters through Catalytic Asymmetric Michael Addition of 4‐Oxo‐4‐arylbutenoates

Highly enantioselective Michael addition of 1,3‐dicarbonyl compounds and nitromethane to 4‐oxo‐4‐arylbutenoates catalyzed by N,N′‐dioxide–Sc(OTf)₃ complexes has been developed. Using 0.5–2 mol % catalyst loading, various α‐stereogenic esters were obtained regioselectively with excellent yields (up to 97 %) and enantioselectivities (up to >99 % ee). Moreover, the reaction performed well under nearly solvent‐free conditions. The products with functional groups are ready for further transformation, which showed the potential value of the catalytic approach. According to the experimental results and previous reports, a plausible working model has been proposed to explain the origin of the activation and the asymmetric induction.     

Eine neuartige Fragmentierung cyclischer α, ß-ungesättigter Carbonylsysteme; Synthese von Exalton und rac-Muscon aus Cyclododecanon Vorläufige Mitteilung

The conversion of bicyclo[10.3.0]-1,12-epoxy-13-pentadecanone into 4-cyclopenta-decyne-1-one, effected by p-tolylsulfonylhydrazine under mild conditions and in high yield, provides an example of a new fragmentation reaction.     

Synthesis,characterization and spectral studies of various newer 4‐benzyloxy‐1H‐indole‐2‐carboxylic acid (arylidene)‐hydrazides

4‐Benzyloxyindole‐2‐carboxylic acid hydrazide reacts with aromatic and heterocyclic aldehydes in alcoholic medium in refluxing conditions to give 4‐benzyloxy‐1H‐indole‐2‐carboxylic acid (arylidene)‐hydrazides, important synthetic intermediates for the synthesis of a newer class of pharmacologically active compounds. We describe here the synthesis of various 4‐benzyloxy‐1H‐indole‐2‐carboxylic acid (arylidene)‐hydrazides by conventional as well as microwave irradiation techniques. The structures of these compounds have been confirmed by spectroscopic techniques (FTIR, NMR and MS). Some of the interesting features of the electron impact mass spectral fragmentation pattern of these compounds are also discussed.