Behaviour of the Primary Nitro Group Under Denitration Conditions

ABSTRACT

Treatment of per-O-acetylated or acetalated glycosylnitromethanes derived from the common hexoses and pentoses with tributyltin hydride and a catalytic amount of a radical initiator [1,1′-azobis(cyclohexanecarbonitrile)] in refluxing benzene easily afforded the corresponding glycosylmethanal oximes in 84-97% yields. Per-O-acetylated C-β-glycopyranosylmethanal oximes were employed for synthesis of versatile C-β-glycopyranosyl cyanides of the β-D-gluco, β-D-manno, β-D-galacto, β-D-xylo, and β-L-rhamno configurations.     

Sonochemical Preparation of Dipicolinamide Mn‐complexes and Their Application as Catalysts Towards Sono‐synthesis of Ketones

A series of non‐heme Mn‐complexes has been synthesized by the sonication of manganese (II)chloride and bis‐amides (condensation products of 2‐picolinic acid and o‐phenylenediamines). The Mn‐complexes effectively promote the oxidation of unactivated aliphatic and benzylic C─H and N‐bearing heterocycles substrates with low catalyst loading using eco‐friendly hydrogen peroxide in the presence of acetic acid as additive under ultrasonic irradiation. Chromatographic studies revealed that the corresponding ketones are the only detectable products. Noteworthy, the presence of electron donors in the catalyst structure significantly increased the reaction yields. The substantial lowering of the oxidation reaction yields by adding ionol (2,6‐di‐tert‐butyl‐4‐methylphenol) as a free radical trap suggesting a free radical reaction pathway.     

Photolysis of 2,6 di-tert-butyl-4-tert-butylperoxy-4-methyl-2,5-cyclohexadienone

The photolysis of a heptane solution of 2,6-di-tert-butyl-4-tert-butylperoxy-4-methyl- 2,5-cyclohexadienone (1) with light of 360–480 nm in the presence of 2,6-di-tert-butyl-4-methylphenol or 2,4,6-tri-tert-butylphenol gives rise to their corresponding phenoxyls in a reaction with the tert-butoxyl arising in the photolysis. Direct evidence of the formation of t-BuO^. by the photolysis of 1 was provided by the ESR characterization of spin-adducts of this radical with nitrosobenzene and nitrosodurene. Evidence of the photolysis of the peroxide bond in 1 is important for the mechanism of reaction of phenolic chain-breaking antioxidants.     

From Lianas to Glycobiology Tools: Twenty-Five Years of 2,5-Dideoxy-2,5-imino-D-mannitol

Summary.  2,5-Dideoxy-2,5-imino-D-mannitol (DMDP) has been isolated from several natural sources. Many synthetic approaches are available, and many derivatives have been synthesized and their biological activities have been investigated. An overview on isolation, syntheses, and biological data of DMDP as well as some closely related compounds will be given in this review. Received November 14, 2001. Accepted November 19, 2001     

Thietanyl protection in the synthesis of 1-alkyl-8-bromo-3-methyl-3,7-dihydro-1<Emphasis Type="Italic">H</Emphasis>-purine-2,6-diones

The protection of the 7-NH group in 8-bromo-3-methyl-3,7-dihydro-1H-pyrine-2,6-dione during the synthesis of 7-ubsubstituted 1-alkyl-8-bromo-3-methyl-3,7-dihydro-1H-pyrine-2,6-diones with a thienyl group was applied that was introduced by the reaction with 2-chloromethylthiirane. The thietanyl protection was removed by treating with sodium alcoholate after the oxidation with hydrogen peroxide to thietane 1,1-dioxide group.     

Oxidation reactions of some natural volatile aromatic compounds: anethole and eugenol

trans-Anethole [1-methoxy-4-(trans-prop-1-en-1-yl)benzene] was isolated from anise seed oil (Pimpinella anisum). Its photochemical oxidation with hydrogen peroxide gave the corresponding epoxy derivative together with 4-methoxybenzaldehyde. The thermal oxidation of trans-anethole with 3-chloroperoxybenzoic acid at room temperature resulted in the formation of dimeric epoxide, 2,5-bis(4-methoxyphenyl)-3,6-dimethyl-1,4-dioxane, as the only product. Photochemical oxygenation of trans-anethole in the presence of tetraphenylporphyrin, Rose Bengal, or chlorophyll as sensitizer led to a mixture of 1-(4-methoxyphenyl)prop-2-en-1-yl hydroperoxide and 4-methoxybenzaldehyde. Eugenol was isolated from clove oil [Eugenia caryophyllus (Spreng.)]. It was converted into 2-methoxy-4-(prop-2-en-1-yl)phenyl hydroperoxide by oxidation with hydrogen peroxide under irradiation. Thermal oxidation of eugenol with 3-chloroperoxypenzoic acid at room temperature produced 2-methoxy-4-(oxiran-2-ylmethyl)phenol, while sensitized photochemical oxygenation (in the presence of Rose Bengal or chlorophyll) gave 4-hydroperoxy-2-methoxy-4-(prop-2-en-1-yl)cyclohexa-2,5-dien-1-one. Published in Russian in Zhurnal Organicheskoi Khimii, 2008, Vol. 44, No. 6, pp. 834–841. The text was submitted by the authors in English.     

Synthesis of 15‐Cyano‐12‐oxopentadecano‐15‐lactone and 15‐Cyano‐ 12‐oxopentadecano‐15‐lactam

15‐Cyano‐12‐oxopentadecano‐15‐lactone was synthesized in 59% total yield starting from 2‐nitrocyclododecanone by Michael addition to acrylaldehyde, followed by reaction with trimethylsilylcyanide, hydrolysis, ring‐expansion, and Nef reaction. A two‐step, one‐pot synthesis of intermediate 2‐hydroxy‐4‐(1‐nitro‐2‐oxycyclododecyl)butanenitrile from 3‐(1‐nitro‐2‐oxocyclododecyl)propanal was developed and the conditions for the Nef reaction were studied. 15‐Cyano‐12‐oxopentadecano‐15‐lactam was synthesized in 40% total yield starting from 2‐nitrocyclododecanone by Michael addition to acrylaldehyde, followed by Strecker reaction, ring‐expansion, and Nef reaction. The conditions for the Strecker and Nef reactions were studied. The structures of the target compounds, intermediates, and by‐product were characterized by IR, ¹H‐ and ¹³C‐NMR, and elemental analysis or MS.     

Ozonation of 1,1,2,2‐Tetraphenylethene Revisited: Evidence for Electron‐Transfer Oxygenations

Ozonolyses of 1,1,2,2‐tetraphenylethene (TPE, 1 ) have been described many times in the literature, but the reports are contradictory. This reaction is particularly important for understanding the mechanism of alkene ozonolysis, in view of possible stabilization of reactive intermediates by aryl groups. Thus, systematic investigations of ozonolysis in both aprotic solvents and in protic solvents are reported here. Attention is directed to the following details that have been underestimated in the past: i) the actual electronic structure of ground‐state ozone (O₃), ii) differentiation between strained and unstrained alkenes, iii) the significance of both the O₃ concentration and the TPE concentration, iv) the influence of various solvents, including pyridine, v) the influence of the reaction temperature, vi) the role of electron‐transfer catalysis (ETC) and, vii) the effect of structural modifications. Our results suggest that ozonolysis of TPE ( 1 ) does not include a 1,3‐dipolar reaction step, but represents a particularly interesting example of electron‐donor (TPE)/electron‐acceptor (O₃) redox chemistry. The present investigations include several crucial results. First, pure 3,3,6,6‐tetraphenyltetroxane ( 3 , m.p. 221° (dec.)) and pure tetraphenylethylene ozonide ( 4 , m.p. 153° (dec.)) are prepared for the first time, although 3 and 4 have long been known. Second, the singlet diradical character of O₃, lessened by means of hypervalent‐electron interaction and predicted by different calculations, is evidenced via reaction with the spin‐trap galvinoxyl (2,6‐bis(1,1‐dimethylethyl)‐4‐{[3,5‐bis(1,1‐dimethylethyl)‐4‐oxocyclohexa‐2,5‐dien‐1‐ylidene]methyl}phenoxy; 8 ), and the zwitterionic reaction behavior of ground‐state O₃ is ruled out. Third, the electron‐acceptor ability of O₃ is evidenced by reactions with suitable tetraaryl ethylenes: it is enhanced by addition of catalytic amounts of protons or Lewis acids. Fourth, the observed distribution of the O₃ O‐atoms to the two different olefinic C‐atoms of the unsymmetric alkene 27b is in full agreement with an initial single‐electron transfer (SET) step, followed by a radical mono‐oxygenation to cause the crucial C,C cleavage. Final dioxygenation should lead to the generally known products (ozonides, tetroxanes, hydroperoxides). The regioselectivity is found to be inconsistent with the expected decay of an intermediate primary ozonide. Finally, the treatment of 1,2‐bis(4‐methoxyphenyl)acenaphthylene ( 36 ) with O₃ (simultaneous transfer of three O‐atoms) leads to the same experimental result as a stepwise transfer of one O‐atom followed by a transfer of two O‐atoms.     

An Unusual Rearrangement and its Dependence on Configuration

In the course of a synthetic study, we encountered an unusual rearrangement that we now report, one that involves a 5‐nitronorbornenyl system having 7‐endo‐ and 7‐exo‐pyridin‐2‐yl groups being treated under Nef‐reaction conditions. The stereoisomers differ in their Nef‐reaction behavior: the isomer with the pyridin‐2‐yl group exo to the NO₂ moiety primarily affords the Nef reaction, however, with formation of a rather unusual rearrangement side‐product. The endo‐pyridyl stereoisomer proceeded exclusively with rearrangement.     

Tetrahydrofurane und Lactone,I. Synthese und Reaktionen chiraler 2,5-überbrückter Tetrahydrofurane – ein neuer Weg zu optisch aktiven γ-Lactonen und γ-Bislactonen

Tetrahydrofurans and Lactones, I. - Synthesis and Reactions of Chiral 2,5-Bridged Tetrahydrofurans - A New Approach to Optically Active γ-Lactones and γ-Bislactones Diels-Alder reaction of 3,4-hexamethylenefuran with acrylic acid gives the carboxylic acid 1a with high endo selectivity. 1a was separated into the enantiomers via the α-phenylethylammonium salts. Comparison of the CD spectra of (−)- 1a and (−)- 3 and the X-ray structural analysis of the camphanoyl derivative (−)- 4b lead to the 1R,2S,4S configuration of (−)- 1a as well. The 2,5-bridged tetrahydrofuran (−)- 5 with all-cis and RSS configuration is obtained by ozonolysis of the ester (−)- 1b . (−)- 5 can be oxidized to the γ-lactone (2R,3S)-(−)- 6 with sodium metaperiodate/potassium permanganate in 22% yield. Hydride reduction of (−)- 6 under various conditions leads to the γ-bislactones (−)- 8 and (−)- 9 or to the bislactol (−)- 10 . (−)- 8 has the same absolute configuration as the naturally occuring (−)-canadensolide.     

The catalytic ozonization of model lignin compounds in the presence of Fe(III) ions

The ozonization of several model lignin compounds (guaiacol, 2,6-dimethoxyphenol, phenol, and vanillin) was studied in acid media in the presence of iron(III) ions. It was found that Fe³⁺ did not influence the initial rate of the reactions between model phenols and ozone but accelerated the oxidation of intermediate ozonolysis products. The metal concentration dependences of the total ozone consumption and effective rate constants of catalytic reaction stages were determined. Data on reactions in the presence of oxalic acid as a competing chelate ligand showed that complex formation with Fe³⁺ was the principal factor that accelerated the ozonolysis of model phenols at the stage of the oxidation of carboxylic dibasic acids and C₂ aldehydes formed as intermediate products.     

Design and Synthesis of Two Aromatic Amines with Dendritic Structure

The design and synthesis of two aromatic amines with dendritic structures, i.e. 3,4,5‐tribenzyloxyaniline (3,4,5‐G₁‐NH₂) and 2,5‐dibenzyloxyaniline (2,5‐G₁‐NH₂), were conducted. A coupling reaction of three or two equivalents of benzyl bromide to one equivalent of methyl hydroxybenzoate generated methyl 3,4,5‐tribenzyloxybenzoate (3,4,5‐G₁‐COOCH₃), methyl 2,5‐dibenzyloxybenzoate (2,5‐G₁‐COOCH₃) and 2,6‐dibenzyloxybenzoate (2,6‐G₁‐COOCH₃) in high yields. All G₁‐COOCH₃ derivatives were studied by X‐ray analysis. The results show that these dendrons have sufficient volume to be used as the fine ligands for certain catalysts. The amide intermediates (benzamide, G₁‐CONH₂) were obtained by reaction between ammonia and G₁‐COOCH₃. Interestingly, 2,6‐dibenzyloxybenzamide (2,6‐G₁‐CONH₂) can not be prepared in the same condition, which may be due to the overlarge steric block. Sodium hypochlorite was an effective oxidant to generate methyl carbamates G₁‐ NHCO₂CH₃.     

Dynamic 1H NMR Study of Aryl-Nitrogen Single Bond and Carbon-Carbon Double Bond Rotational Energy Barriers in Two Highly Functionalized Pyranopyrimidines

Summary.  The reactive 1:1 intermediate produced in the reaction between 2,6-dimethylphenyl isocyanide and dimethyl acetylenedicarboxylate was trapped by N,N′ -dimethylbarbituric acid to yield the isomeric products dimethyl 7-(2,6-dimethylphenylamino)-1,3-dimethyl-2,4-dioxo-4H-pyrano[3,2-d]pyrimidine-5,6-dicarboxylate and dimethyl (E)-2-((2,6-dimethylphenylamino)-(1,3-dimethyl-2,4,6-trioxo-pyrimidine-5-ylidene)-methyl)-but-2-enedioate in a nearly 1:1 ratio and an overall yield of 85%. Dynamic effects were observed in the ¹H NMR spectra of these compounds and were attributed to restricted rotation around the aryl-nitrogen single bonds and the polarized carbon-carbon double bond. Received September 18, 2000. Accepted (revised) November 22, 2000     

On the Stereochemistry of Vincetene

Summary.  The absolute configuration of the centre of asymmetry in the side chain of the alkaloid vincetene (1) was determined by ozonolysis and subsequent unequivocal transformations affording the (S)-enantiomer of 1,2-propanediyl dibenzoate (4). Received February 22, 2001. Accepted March 1, 2001     

RuO4-mediated oxidation of N-benzylated tertiary amines. 3. Behavior of 1,4-dibenzylpiperazine and its oxygenated derivatives

1,4-Dibenzylpiperazine (1),-2-piperazinone (7),-2,6-piperazinedione (9), and 1-benzoyl-4-benzylpiperazine (30) were oxidized by RuO₄ (generated in situ) by attack at their endocyclic and exocyclic (i.e., benzylic) aminic N-α-C-H bonds to afford various oxygenated derivatives, including acyclic diformamides, benzaldehyde, and benzoic acid. The reaction outcome was complicated by (i) the hydrolysis of diformamides, occurred during the work-up, and (ii) the reaction of benzaldehyde with the hydrolysis-derived amines giving imidazolidines and/or Schiff bases. Benzoic acid resulted from benzaldehyde only. Compounds 7, 30, and 1-benzylpiperazine, but not 9, were transiently formed during the oxidation of 1. In the same reaction conditions, 1,4-dibenzyl-2,3-(or 2,5)-piperazinedione, 1,4-dibenzyl-2,3,6-piperazinetrione, 4-benzyol-1-benzyl-2-piperazinone, and 1,4-dibenzoylpiperazine were inert. The proposed oxidation mechanism involves the formation of endocyclic and exocyclic iminium cations, as well as of cyclic enamines. The latter intermediates probably result by base-induced deprotonation of the iminium cations, provided an N ⁺−β-proton is available. In the case of 1, the cations were trapped with NaCN as the corresponding α-aminonitriles. The statistically corrected regioselectivity (endocyclic/exocyclic) of the RuO₄-induced oxidation reaction of 1, 7, and 30 was 1.2–1.3.     

间位苯基桥联的锰(Ⅲ)双咔咯的合成、表征及催化氧化性质(英文)

通过间苯二甲醛与5-氟苯基二吡咯甲烷反应合成了一种新的间位苯基桥联的双咔咯1,并利用锰盐与自由咔咯反应制备了其锰的金属配合物2。采用紫外、质谱、核磁、XPS等手段对化合物进行了表征。以苯乙烯为底物考察了锰双咔咯2的催化氧化性质,探讨了时间、溶剂、氧源、轴向配体对催化反应的影响。结果表明以亚碘酰苯和间氯过氧苯甲酸为氧源时催化的主要产物为环氧苯乙烷,而以双氧水和叔丁基过氧化氢为氧源时则主要产物为苯甲醛;在极性溶剂中的催化氧化产率较高。轴向配体对催化氧化有促进作用,不同轴向配体对催化反应产率提高的顺序是:1-甲基咪唑吡啶咪唑。     

Murexide reaction of caffeine with hydrogen peroxide and hydrochloric acid. II

In continuation of the study on the murexide reaction of caffeine with 3% hydrogen peroxide/hydrochloric acid and then with ammonia giving a purple coloration, we investigated the oxidation reaction of caffeine with 6% hydrogen peroxide/hydrochloric acid to isolate ten reaction products, 3-hydroxy-4,6-dimethyloxazolo[4,5-d]pyrimidine-2,5,7(3H,4H,6H)-trione 1 , 1,3-dimethylalloxan 2 , murexoin 3 , 1,3,7-trimethyl-2,6,8-trioxo-9-hydroxy-1H,3H,7H-xanthine 5 , 1,3,7-trimethyl-2,6,8-trioxo-1H,3H,7H-xanthine 6 , 1,3,7-trimethyl-2,6-dioxo-8-chloro-1H,3H,7H-xanthine 7, 5-(1,3-dimethyl-1,2,3,4,5,6-hexahydro-2,4,6-trioxopyrimidin-5-yl)-aminomethylene-1,3-dimethyl-1,2,3,4,5,6-hexahydro-2,4,6-trioxopyrimidine ammonium salt 9 , 1,3-dimethylpalabanic acid 10 , 1-methyl-2,4,5-trioxoimidazole 11 , 3-hydroxy-5,7-dimethyloxazolo[5,4-d]pyrimidine-2,4,6(3H,5H,7H)-trione 12 and 4,6,8-trimethyl-1,2,4-dioxazino[6,5-d]pyrimidine-3,5,7(4H,6H,8H)-trione 13 . The oxidation reaction using 6% hydrogen peroxide/hydrochloric acid was found to produce a similar purple coloration to that of the murexide reaction despite no subsequent addition of ammonia, indicating the liberation of ammonia by the oxidation of caffeine. Among the above compounds, the purple colored substance murexoin 3 and the yellow colored compound 9 were both ammonium salts, and compound 5 was the red colored substance. In the present investigation, these three compounds were found to contribute to the coloration.     

单核Zn(Ⅱ)/Ni(Ⅱ)含氮配体配合物的合成、晶体结构及性质

合成了2个新的配合物[Zn(BPP)2(H2O)4](2,6-NDS)·0.5H2O(1)和[Ni(phen)2(H2O)2](A-2,5-DSA)·3H2O(2)(2,6-NDS=2,6-萘二磺酸根,A-2,5-DSA=苯氨-2,5-二磺酸根,BPP=1,3-二(4-吡啶基)丙烷,phen=1,10-邻菲咯啉),用X-射线单晶衍射结构分析方法测定了配合物的晶体结构。配合物1是单核分子,Zn2+离子与2个1,3-二(4-吡啶基)丙烷的2个N原子及4个水分子配位,形成单核配位阳离子。相邻配位阳离子通过配位水分子与氮原子的氢键作用联接成一维双螺旋阳离子链。双螺旋阳离子链与未配位的2,6-萘二磺酸根阴离子通过氢键作用形成二维超分子网。配合物2是单核分子,Ni2+离子与2个1,10-邻菲咯啉分子中的4个N原子及2个水分子配位,形成单核配位阳离子。配位阳离子与游离的水分子及苯氨-2,5-二磺酸根阴离子通过氢键作用构筑成二维超分子网。     

Sulfonated Condensed Polynuclear Aromatic (S-Copna) Resin Catalyzed Selective Oxidation of Sulfides to Sulfoxides or Sulfones Using Hydrogen Peroxide

Abstract

Sulfonated condensed polynuclear aromatic (S-COPNA) resin was found to be a highly efficient, environmentally friendly, recyclable heterogeneous catalyst for the oxidation of alkyl and aryl sulfides to the corresponding sulfoxides or sulfones, in good yields under mild reaction conditions using 30% hydrogen peroxide as an oxidant.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental resource: Synthesis of the S-COPNA resin catalyst. Spectroscopic data for compounds.     

Fast Hydrocarbon Oxidation by a High-Valent Nickel–Fluoride Complex

In the search for highly reactive oxidants we have identified high-valent metal–fluorides as a potential potent oxidant. The high-valent Ni–F complex [Ni^III(F)(L)] ( 2 , L=N,N′-(2,6-dimethylphenyl)-2,6-pyridinedicarboxamidate) was prepared from [Ni^II(F)(L)]⁻ ( 1 ) by oxidation with selectfluor. Complexes 1 and 2 were characterized by using ¹H/¹⁹F NMR, UV-vis, and EPR spectroscopies, mass spectrometry, and X-ray crystallography. Complex 2 was found to be a highly reactive oxidant in the oxidation of hydrocarbons. Kinetic data and products analysis demonstrate a hydrogen atom transfer mechanism of oxidation. The rate constant determined for the oxidation of 9,10-dihydroanthracene (k₂=29 m ⁻¹ s⁻¹) compared favorably with the most reactive high-valent metallo-oxidants. Complex 2 displayed reaction rates 2000–4500-fold enhanced with respect to [Ni^III(Cl)(L)] and also displayed high kinetic isotope effect values. Oxidative hydrocarbon and phosphine fluorination was achieved. Our results provide an interesting direction in designing catalysts for hydrocarbon oxidation and fluorination