<Emphasis Type="Italic">N</Emphasis>-Bromo Reagent Mediated Oxidation of Urazoles to Their Corresponding Triazolinediones under Mild and Heterogeneous Conditions

Summary. Various N-bromo reagents [HMTAB, DABCO-bromine, DPTBE, and TBCA] were used as effective oxidizing agents for the oxidation of urazoles and bisurazoles to their corresponding triazolinediones under mild and heterogeneous conditions at room temperature with good to excellent yields. Also the oxidation of some new 4-phenylurazole derivatives with these reagents is discussed.     

Poly[N-(2-aminoethyl)acrylamido] triethylammonium polyhalide derivatives: Preparation and synthetic applications

Poly[N-(2-aminoethyl)acrylamido]triethylammonium dichloroiodate, tetrachloroiodate, and dibromoiodate polyhalides were developed as a new class of solid phase organic reagents. N,N′-methylenebisacrylamide crosslinked polyacrylamide support was utilized to prepare the reagents. The utility of polyhalide reagents for the α-halogenation of carbonyl compounds and oxidation of alcohols at various reaction conditions is described. The reactivity of the polyhalide reagents increased considerably in polar solvents and the optimum temperature for conducting the reactions was 30°C. Studies on halogenation and oxidation reactions using differently crosslinked polyacrylamide-based polyhalide reagents revealed that the reactivity increased up to 10% crosslinking and decreased progressively on further increase in the degree of crosslinking. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1413–1421, 1997     

Transition‐Metal‐Free Cross‐Coupling of Benzothiophenes and Styrenes in a Stereoselective Synthesis of Substituted (E,Z)‐1,3‐Dienes

A transition metal‐free one‐pot stereoselective approach to substituted (E,Z)‐1,3‐dienes was developed by using an interrupted Pummerer reaction/ligand‐coupling strategy. Readily available benzothiophene S‐oxides, which can be conveniently prepared by oxidation of the parent benzothiophenes, undergo Pummerer coupling with styrenes. Reaction of the resultant sulfonium salts with alkyllithium/magnesium reagents generates underexploited hypervalent sulfurane intermediates that undergo selective ligand coupling, resulting in dismantling of the benzothiophene motif and the formation of decorated (E,Z)‐1,3‐dienes.     

Regiospecific oxidation of polycyclic aromatic phenols to quinones by hypervalent iodine reagents

The hypervalent iodine reagents o-iodoxybenzoic acid (IBX) and bis(trifluoro-acetoxy)iodobenzene (BTI) are shown to be general reagents for regio-controlled oxidation of polycyclic aromatic phenols (PAPs) to specific isomers (ortho, para, or remote) of polycyclic aromatic quinones (PAQs). The oxidations of a series of PAPs with IBX take place under mild conditions to furnish the corresponding ortho-PAQs. In contrast, oxidations of the same series of PAPs with BTI exhibit variable regiospecificity, affording para-PAQs where structurally feasible and ortho-PAQs or remote PAQ isomers in other cases. The structures of the specific PAQ isomers formed are predictable on the basis of the inherent regioselectivities of the hypervalent iodine reagents in combination with the structural requirements of the phenol precursors. IBX and BTI are recommended as the preferred reagents for regio-controlled oxidation of PAPs to PAQs.     

Reactions of metallated 1-hydroxy-2,2,4,5,5-pentamethyl-3-imidazoline with electrophiles

Reactions of metallated 1-hydroxy-2,2,4,5,5-pentamethyl-3-imidazoline with electrophilic reagents followed by oxidation result in mono- and bifunctional substituted nitroxides of 3-imidazoline and an imidazolidine series including enaminocarbonyl and -thiocarbonyi derivatives and enaminoimines, the spin-labeled chelating reagents.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1612–1616, September, 1993.     

Synthesis and Addition Reactions of 1,3-Thiazole-5(4H)-thione Oxides

1,3-Thiazole-5(4H)-thione oxides 2 were prepared by oxidation of the corresponding 1,3-thiazole-5(4H)-thiones 1 with m-chloroperbenzoic acid (Table 1). Addition reactions of 2 with organolithium and Grignard reagents yielded 4,5-dihydro-4,4-dimethyl-1,3-thiazol-5-yl methyl sulfoxides of type 4 via thiophilic attack (Table 2). Whereas the reaction with the organolithium compounds proceeded with fair-to-excellent yields, the Grignard reagents reacted only very sluggishly. The sulfoxides 4 could also be prepared via oxidation of 4,5-dihydro-4,4-dimethyl-5-(methylthio)-1,3-thiazoles of type 3 with m-chloroperbenzoic acid, together with the corresponding sulfones 5 (Scheme 1).     

铜络合物催化的格氏试剂不对称1,4-共轭加成反应研究进展

铜络合物催化的有机金属试剂与α,β-不饱和羰基化合物的1,4-共轭加成反应, 是形成新的C—C键的重要方法之一. 介绍了铜络合物催化的格氏试剂与α,β-不饱和羰基化合物的立体选择性1,4-共轭加成反应的研究进展.     

Structure of zinc-5,15-di(o-methoxyphenyl)octaalkylporphyrines and their reaction with organic peroxides in the presence of pyridine

By combined spectral and calculation methods the structure of zinc 5,15-di(o-methoxyphenyl)-2,8,12,18 3,7,13,17-octaalkylporphyrinates (I, II) and their properties in the reaction with organic peroxides with addition of different amounts of pyridine were studied. The reaction of zinc porphyrinates with peroxides in the presence of pyridine leads to destruction of the complex chromophore. Kinetic parameters of the investigated reaction (effective k _ef and true k _V rate constants) are obtained. The presence of base in the reaction medium is found to lead to a change in the structure of the zinc porphyrinates and affects the rate of oxidation. By quantum-chemical method PM3 the geometry of the reagents was calculated and the deformation distortions of the reactants molecules and intermediates in the course of the oxidation reaction was demonstrated. The influence of electronic effects of substituents and the degree of deformation of the zinc porphyrinate macrocycle on their redox properties is revealed.     

Dual thiophilic or carbophilic reactivity of N,N-dialkyl perfluorocarboxylic thioamides with organometallic reagents

N,N-dialkyl amides of perfluorothiocarboxylic acids react with organomagnesium and organolithium reagents via thiophilic or carbophilic attack of carbanion on the CS bond. The chemoselectivity depends on the nature of the organometallic species. Lithium reagents react at sulfur, with a subsequent β-elimination of fluoride, giving an N,S-ketene acetal. Simple organomagnesium reagents do not react, whereas allylmagnesium halide reacts at carbon, giving an adduct which can be trapped by methyl iodide and converted to the corresponding N,S-acetal. The latter can be transformed into a perfluoroalkyl dienamine via oxidation.     

2-Nitroguanidine Derivatives: VI. Synthesis and Chemical Properties of Hydrazo- and Azobis(nitroformamidine)

New methods have been proposed for the synthesis of hydrazobis(nitroformamidine), and its reactions with electrophilic reagents, formaldehyde and glyoxal, have been studied. Oxidation of hydrazobis-(nitroformamidine) with atmospheric oxygen in glacial acetic acid in the presence of a catalytic amount of N2O4 gives crystalline azobis(nitroformamidine). Ionization constants of the oxidation product, determined by potentiometric titration (pKa ¹ = 3.50, pKa ² = 7.93), indicate considerable increase in the NH acidity as compared to 2-nitroguanidine. Reactions of azobis(nitroformamidine) with -dicarbonyl compounds lead to formation of 1-diacylmethyl-N' ¹,N' ²-dinitrohydrazine-1,2-dicarboximidamides.     

A NEW AND SHORT SYNTHESIS OF 7 H-BENZO[a]CYCLOHEPTEN-7-ONE AND SOME DERIVATIVES: OXIDATION OF 7-BROMO-5H-BENZO[a]CYCLOHEPTENE

Oxidation of 7-bromo-5H-benzo[a]cycloheptene with some oxidation reagents has been studied. Several 2,3- and 4,5-benzotropone derivatives has been obtained. The structures of the products were determined by ¹H-, ¹³C NMR data and chemical transformation.     

Efficient Chemoselective Oxidation of Phenylmethanols to Aldehydes with Iodosobenzene

Summary. Primary phenylmethanols are selectively and efficiently oxidized to the corresponding aldehydes by the system C₆H₅IO/(C₆H₅)₄PBr/CH₂Cl₂, T = 298 K under aerobic conditions. The use of the relatively stable iodosobenzene, an iodine(III) compound, in place of the usually employed and potentially explosive iodine(V) reagents, the easy work-up procedure, and the facile recycling of solvent and oxidant provides a convenient and environmentally benign oxidation method.     

Hydrodebromination of bromoarenes using Grignard reagents catalyzed by metal ions

The metal salts, FeCl^·₂4H₂O, FeCl₃, NiCl₂, CoCl₂, CuBr and some iron complexes were found to be efficient catalysts for hydrodebromination of bromoarenes under mild reaction conditions with two equivalents of Grignard reagents. Among them, the iron systems showed the best behavior regarding economic and environmental considerations. All the alkyl Grignard reagents (except CH₃MgCl) and p‐tolylMgBr were promising reductive reagents with the formation of their homo‐coupling products. Copyright © 2008 John Wiley & Sons, Ltd.     

An efficient method for 3,4-dihydroisoquinolinium ion formation,leading to a facile introduction of nucleophiles

The ketene silyl acetal derived from ethyl 2-benzyltetrahydroisoquinoline-1-carboxylate undergoes a rapid oxidation reaction with N-bromosuccinimide to form 3,4-dihydroisoquinolinium ion, which reacts with Grignard reagents to give 1,1-disubstituted tetrahydroisoquinolines in good yields.     

Phase‐vanishing methods based on fluorous phase screen: A simple way for efficient execution of organic synthesis

The phase‐vanishing (PV) method is based on spontaneous reaction controlled by diffusion of reagents into fluorous media, such as perfluorohexanes (FC‐72) and polyperfluoroethers. Thus, the original PV reaction utilizes a triphasic test tube method composed of a bottom reagent phase, a middle fluorous phase, and a top substrate phase. In such a triphasic system, the fluorous phase acts as a liquid membrane to transport the bottom reagents to the top organic phase containing substrates. In the end, the bottom layer disappears and two phases remain. Since the first demonstration of the PV method by bromination of alkenes with molecular bromine, a number of applications have been developed thus far. These include halogenation of alcohols with SOBr₂ and PBr₃, demethylation of methoxyarenes with BBr₃, cyclopropanation of alkenes by CH₂I₂‐AlEt₃, and Friedel–Crafts acylation of aromatic compounds with SnCl₄. A fluorous triphasic U‐tube method is effective for chlorination of alcohols based on lighter (less dense) reagents such as SOCl₂ and PCl₃. A system using a solution containing reagents as a bottom phase is useful for oxidation with m‐CPBA, which may be defined as a new category for the “extractive PV” method. Recent advances include a “quadraphasic” PV method, in which an aqueous “scavenger” phase is added to the original triphasic PV method to remove acidic by‐products. © 2008 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 8: 351–363; 2008: Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.20161     

Phenylselenoacetaldehyde,a Useful Reagent for the Homologative Conversion of Halides to Phenylselenomethyl Ketones

The conversion of primary, secondary and vinylic halides to the two C-atoms homologated phenylselenomethyl ketones 8 is described. The method involves addition of the readily available phenylselenoacetaldehyde 5 to the Grignard reagents 9 and oxidation of the resulting β-hydroxy-selenides 10 (Scheme 3).     

Efficient Chemoselective Oxidation of Phenylmethanols to Aldehydes with Iodosobenzene

Primary phenylmethanols are selectively and efficiently oxidized to the corresponding aldehydes by the system C₆H₅IO/(C₆H₅)₄PBr/CH₂Cl₂, T = 298 K under aerobic conditions. The use of the relatively stable iodosobenzene, an iodine(III) compound, in place of the usually employed and potentially explosive iodine(V) reagents, the easy work-up procedure, and the facile recycling of solvent and oxidant provides a convenient and environmentally benign oxidation method.     

Syntheses and Antimicrobial Activity of Some Novel 6‐Substituted Dibenzo[d,f][1,3,2]dioxaphophepin‐6‐oxides,Sulfides, and Selenides

6‐Substituted‐dibenzo[d, f][1,3,2]dioxaposphepin‐6‐oxides, sulfides, and selenides (5a–i, 6a–d, and 7a–d) were synthesized by reacting 2,2′‐biphenol (1) with phosphorus tribromide in the presence of triethylamine at 0–30°C and subsequent reaction of the monobromide (2) with different Grignard reagents (3) at room temperature. The products (4) were converted to corresponding oxides, sulfides, and selenides (5a–i, 6a–d, and 7a–d) by oxidation with H₂O₂ at room temperature and refluxing with sulfur and selenium respectively. The chemical structures of all the products were confirmed by analytical, IR, NMR (¹H, ¹³C, and ³¹P), and mass spectral data. Most of these compounds exhibited moderate antimicrobial activity.     

Functionalization at C-12 in labdanic diterpenes: synthesis of the natural diterpenic lactones isolated from cistus ladaniferus L.

Oxidative cyclization of Labdanediol (XII) and methyl Labdanolate (Ib) with Pb(OAc)₄, and subsequent oxidation with reagents as RuO₄, O₃, CrO₃, or (Bu^t)₂ CrO₄ affords, in excellent yield, the natural diterpenic lactones II, III, VII, VIII, XI and XIII, isolated from $\text{Cistus ladaniferus L.}$     

Mild Oxidation of 1,3,5‐Trisubstituted Pyrazolines with N‐Bromo‐sulphonamides

1,3,5‐Trisubstituted pyrazolines to pyrazoles are carried out efficiently in the presence of new reagents N,N,N′, N′‐tetrabromo‐benzene‐1,3‐disulfonylamine [TBBDA] and N,N′‐dibromo‐N,N′‐1,2‐ethanediylbis‐(p‐toluenesulphonamide) [BNBTS] in solvent‐free conditions with catalytic amounts of SiO₂ under microwave irradiation in high yields.