Electrogenerated hypervalent iodine compounds as mediators in organic synthesis

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A versatile synthesis of vicinal diazides using hypervalent iodine

A convenient synthesis of vicinal diazides from olefins using C₆H₅IO/HOAc/NaN₃ is described. A mechanism is proposed which accounts for the stereochemical outcome.     

Effective synthesis of benzyl halides triggered by in situ prepared hypervalent halides

An effective approach for the direct benzylhalogenation with in situ generation of hypervalent halides has been developed.A variety of benzyl halides are produced in moderate to excellent yields(up to 99%) with high regioselectivities.UV absorption spectrum is employed to detect the formation of ferr-butyl hypoiodite.     

Efficient synthesis of quinoxalines with hypervalent iodine as a catalyst

Various biologically important quinoxalines were efficiently synthesized in excellent yields via one-pot reaction between 1,2-diaminobenzenes and internal alkynes. The method utilizes inexpensive and readily available hypervalent iodine source, such as (diacetoxyiodo)benzene (PhI(OAc)₂) and proved to be a better alternative as compared to expensive transition metal catalysts. Quinoxaline 4i [(2-phenyl-3-(3,4,5-trimethoxy phenyl)quinoxaline)] was evaluated for leukemia cancer cell lines and turned out to be a good candidate.     

Oxidative rearrangement of alkenes using in situ generated hypervalent iodine(III)

A novel protocol for the oxidative rearrangement of alkenes using in situ generated hypervalent iodine(III) was developed. This approach uses inexpensive, readily available, and stable chemicals (PhI, mCPBA, and TsOH) giving rearrangement products in yields comparable to those obtained using the more expensive commercially available [hydroxy(tosyloxy)iodo]benzene [HTIB or Koser’s reagent]. Additionally, an alternative protocol for the synthesis of 1-methyl-2-tetralone through the one-step epoxidation/rearrangement of 4-methyl-1,2-dihydronaphthalene using mCPBA and TsOH was developed.     

Practical synthesis of 4′-selenopyrimidine nucleosides using hypervalent iodine

We report herein a synthesis of 4′-selenouridine 12 and 4′-selenocytidine 14, substrates for the synthesis of 4′-selenoRNA. The Pummerer-like reaction between the selenoxide 9 and a silylated uracil afforded the desired 4′-selenouridine derivative 10; however, the chemical yield of 10 was rather low. In addition, the reproducibility of this reaction was poor because of the instability of the selenoxide 9. Improvement of this Pummerer-like reaction to give 10 was achieved when the 4-selenosugar 8 was treated with TMSOTf, 2,6-lutidine and the silylated uracil in the presence of iodosylbenzene.     

Regio- and stereoselective iodoarylation of arylacetylenes using molecular iodine promoted by hypervalent iodine

Iodoarylation of arylacetylenes with electron-rich arenes using a simple reagent system: I₂ and PhI(OCOPh)₂ proceeded regio- and stereoselectively to give trans adducts, 1,1-diaryl-2-iodoethenes, in good to high yields.     

Thermal studies of hypervalent iodine reagents

The use of unconventional synthesis methods in the formation of CaO·2Al₂O₃ (CA₂) is justified because it reduces the formation temperature of the compound. CA₂ is formed by classical method at temperatures above 1,400 °C. The polymeric precursor method allows a significant temperature decrease in CA₂ synthesis reaching temperatures of 1,000 °C. This paper deals with CA₂ synthesis by “citrate” method which is often presented as Pechini method, starting from a mixture of citric acid, ethylene glycol and calcium, and aluminum nitrates. A method based on the formation of a polymeric precursor was also used, starting from a mixture of acrylic acid and nitrates of calcium and aluminum. The results showed a net difference in favor of samples obtained from acrylic acid, which by annealing at 800 °C for 1 h, contain pure CA₂. The samples obtained from citric acid, after annealing at 800 °C are amorphous. After annealing at 900 °C in all samples CA₂ is single phase.     

New hypervalent iodine reagents for electrophilic trifluoromethylation and their precursors: synthesis, structure, and reactivity

Several new five- and a six-membered heterocyclic monochloroiodanes, including two cationic species, were synthesized. Three of which were used for the preparation of corresponding trifluoromethylation reagents. These compounds were characterized by X-ray crystallography for a comparative structural study. A reactivity study on the trifluoromethylation of para-toluenesulfonic acid has been conducted in order to compare initial rates. Compounds having a longer I-O bond display a higher reactivity.     

Direct formation of cyclic sulfates utilising hypervalent iodine species and sulfur trioxide adducts

PhIO reacts with SO₃·DMF at 0°C to form an active sulfating reagent; subsequent addition of alkenes results in the direct formation of cyclic sulfates in moderate to good yield (35-75%). Terminal, 1,1-disubstituted and cyclopentenes participate in the reaction which is technically very straightforward to carry out.     

Stereoselective synthesis of 5-7 membered cyclic ethers by deiodonative ring-enlargement using hypervalent iodine reagents

Stereoselective synthesis of 5-7 membered cyclic ethers was achieved by deiodonative ring-enlargement of cyclic ethers having an iodoalkyl substituent. The reaction took place readily under mild conditions using hypervalent iodine compounds and an acetoxy or a trifluoroacetoxy group was introduced into the rings depending on the hypervalent iodine reagent employed. The use of hexafluoroisopropanol (HFIP) as solvent is critical.     

New chiral hypervalent iodine(V) compounds as stoichiometric oxidants

The synthesis and application of some new hypervalent iodine compounds bearing chiral and achiral ester motives derived from easily accessible starting materials is presented. The oxidation is carried out using dimethyldioxirane as an oxidant providing the desired compounds in moderate to high yields. A crystal structure analysis for one iodine(V) derivative is investigated. The λ⁵-iodanes are applied as stoichiometric reagents in the oxidation of thioanisole to phenylmethyl sulfoxide, benzyl alcohol to benzaldehyde, and meso-hydrobenzoine to benzaldehyde, benzyl, and benzoin.     

Reactions of hypervalent iodine reagents with palladium: mechanisms and applications in organic synthesis

The unique reactivity of hypervalent iodine reagents with Pd0 and PdII complexes has been exploited for a variety of synthetically useful organic transformations. For example, IIII reagents have been used in place of aryl halides for diverse Pd-catalyzed C-C and C-heteroatom bond-forming cross-coupling reactions. In addition, these reagents have found application in Pd-catalyzed oxidation reactions, including the oxidative functionalization of C-H bonds and the 1,2-aminooxygenation of olefinic substrates. This review discusses both the synthetic utility and the interesting mechanistic features of these transformations.     

An efficient synthesis of cyanamide from amine promoted by a hypervalent iodine(III) reagent

In a one-pot strategy we have achieved an efficient method for the synthesis of organic cyanamides starting from dithiocarbamic acid salts/amines. In this strategy the in situ generated alkyl or aryl isothiocyanates, obtained by the desulfurization of dithiocarbamic acid salts with diacetoxyiodobenzene (DIB) react with aqueous ammonia forming alkyl or aryl thiourea which on subsequent oxidative desulfurization with DIB led to the formation of corresponding cyanamide in good yields. Mild reaction conditions, shorter reaction time, an environmentally benign protocol, and easy isolation of the desired product make the present methodology a suitable alternative for the preparation of various organic cyanamides.     

Oxidative synthesis of azacyclic derivatives through the nitrenium ion: application of a hypervalent iodine species electrochemically generated from iodobenzene

Oxidation of the methoxyamide derivatives 1, 4, and 7 has been examined to elaborate efficient synthetic methodology of the azacyclic derivatives 2, 3, 5, 6, and 8, which would be applicable as synthetic intermediates of complicated bioactive substances. In addition to direct anodic and PIFA [phenyliodine(III) bis(trifluoroacetate)] oxidations, an active species derived from iodobenzene generated under electrolytic conditions was examined as an oxidant, and its synthetic efficacy was demonstrated in comparison of the reaction outcomes with other oxidation methods. In the oxidation, the methoxy substitution of substrates modulated the cyclization mode to provide the azaspiro- (2, 8) or quinolinone-type (3, 5, 6) products.     

Direct electrophilic N-trifluoromethylation of azoles by a hypervalent iodine reagent

Effective CF(3) transfer: Various electron-rich nitrogen heterocycles (pyrazoles, triazoles, and tetrazoles) can be directly N-trifluoromethylated by a hypervalent iodine reagent in an efficient manner. The optimized procedure, which includes an in situ silylation of the substrate followed by an acid-catalyzed CF(3) transfer, provides ready access to a series of new and previously challenging or inaccessible NCF(3) compounds.     

Microwave-assisted regioselective synthesis of natural 6-prenylpolyhydroxyisoflavones and their hydrates with hypervalent iodine reagents

Microwave-assisted oxidative rearrangement of 3′-iodotetraalkoxychalcones with hypervalent iodine such as [hydroxy(tosyloxy)iodo]benzene or [bis(trifluoroacetoxy)iodo]benzene, followed by microwave-mediated hydrolysis and in situ cyclization of the resultant acetals gave 6-iodotrialkoxyisoflavones. Pd(0)-catalyzed coupling reaction of the 6-iodoisoflavones with 2-methyl-3-butyn-2-ol under microwave irradiation gave 6-alkynylisoflavones, whose hydrogenation gave the respective hydrates of wighteone, lupisoflavone and derrubone. Wighteone (1a), lupisoflavone (1b) and derrubone (1c) were obtained by dehydration of their respective hydrates under microwave irradiation.     

Rapid aerobic iodination of arenes mediated by hypervalent iodine in fluorinated solvents

Arenes are rapidly converted to the corresponding iodides by aerobic oxidative iodination at room temperature by treatment with iodine and catalytic quantities of nitrous acid in a fluorinated solvent. Dichloroiodic acid is proposed as the actual iodination reagent.