Metal-free oxidative cyclization of urea-tethered alkenes with hypervalent iodine

A metal-free oxidative cyclization of ureas onto unactivated alkenes using iodosylbenzene and an acid promoter is described. The products isolated are predominantly bicyclic isoureas resulting from an intramolecular oxyamination reaction. The acid type and urea substitution have a strong effect on the product formed. A variety of substrates form the isourea with high diastereoselectivity via syn addition including di- and trisubstituted alkenes. Hydrolysis of the isourea gives access to new diastereomerically pure prolinol derivatives.     

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.     

Chiral oxazolidinones as electrophiles: Intramolecular cyclization reactions with carbanions and preparation of functionalized lactams

The intramolecular cyclizations of oxazolidinones with carbanions adjacent to sulfones, sulfoxides, and phosphonates proceed in high yields to obtain functionalized γ and δ lactams. The chiral oxazolidinone precursors can be readily synthesized from commercial amino acids. The lactams from this study are useful synthetic intermediates, as demonstrated by the synthesis of a precursor for levetiracetam, an antiepileptic drug.     

Efficient generation and trapping of acylbenzynes from hypervalent iodine compounds

[5-Acyl-2-(trimethylsilyl)phenyl]iodonium triflates were prepared for the generation of benzynes bearing ketone function. Treatment of the iodonium triflates with Bu₄NF in CH₂Cl₂ in the presence of furan at room temperature gave 6-acyl-1,4-epoxy-1,4-dihydronaphthalenes in high yields. The mild conditions and the tolerance of the ketone function on benzyne generation are attributable to the advantage of hypervalent iodine compounds.     

Metal-free oxidative amide formation with N-hydroxysuccinimide and hypervalent iodine reagents

An oxidative amide formation using N-hydroxysuccinimide and hypervalent iodine reagents was developed. The method enables a wide range of aldehydes and amines to be coupled under mild reaction conditions providing amide in good to excellent yield. The radical species in the reaction mixture was observed for the first time using ESR measurement, and along with other mechanistic investigations, a plausible mechanism of the reaction was proposed.     

Functionalization of cis-1,4-polyisoprene using hypervalent iodine compounds with tetrazole ligands

Hypervalent iodine(III) compounds with tetrazole ligands C₆H₅I(N₄CR)₂ (R  CH₃, C₆H₅, 4-CH₃C₆H₄) reacted, in the presence of elemental iodine, with the double bonds in cis-1,4-polyisoprene (polyIP) to afford iodo-tetrazolylated polymers. The alkyl-iodide groups in the products of the polyIP functionalization were utilized as macro chain-transfer agents for the iodine-transfer polymerization of methyl methacrylate, which yielded brush polymers with well-defined poly(methyl methacrylate) side chains. In addition, the iodo-tetrazolylated polymers were reacted with NaN₃ in DMF at room temperature, and it was noticed that, in addition to nucleophilic substitution, elimination reactions took place. However, the presence of azide groups was taken advantage of and successful click chemistry-type of grafting-onto reactions were carried out with alkyne-capped poly(ethylene oxide) in the presence of CuBr and N,N,N′,N″,N″-pentamethyldiethylenetriamine. The thermal decomposition of both the iodo-tetrazolylated and the azido-tetrazolylated polymers was exothermic, especially for the latter materials. © 2019 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 172–180     

Synthesis,structure and chemical properties of hypervalent germanium compounds,derivatives of lactams with a fragment

The results of studies aimed at elaborating methods for synthesizing penta- and hexacoordinated organogermanium derivatives containing lactamo-N-methyl and related bidentate ligands and investigating their structure and reactivity are reviewed. In these compounds the germanium coordination units include one or two O(or S)-Ge-X or N-Ge-X (X — an electron-deficient group) hypervalent fragments.The review is based on the report at the conference Workshop on the Modern Problems of Heteroorganic Chemistry, Moscow, May 8–13, 1993.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 982–993, June, 1994.     

Intramolecular cyclization of acyl radicals onto the azido group: a new radical approach to cyclized lactams

[reaction: see text] Aryl- and alkyl-derived azidoacyl radicals, generated from thiolesters by intramolecular homolytic substitution at the sulfur, can undergo five- and six-membered cyclization onto the azido moiety to give cyclized lactams.     

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.     

Intramolecular variants of aminomethano desilylation: Reactions of in situ generated immonium ions with allylsilanes

Intramolecular condensation of immonium ions with allylsilanes in aqueous tetrahydrofuran at ambient temperature gives rise to five, six, seven, and eight-membered rings containing nitrogen.     

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.     

Transformation of acridines and azepines into the corresponding 3-oxo-heterocycles by means of hypervalent aromatic iodine compounds

Summary The acridines3,5, and6, as well as the dibenzo[b,f]-azepine4 were converted into the 3-oxo-derivatives7–10 using hypervalent iodine compounds (iodosylbenzene and bis-(trifluoroacetoxy)iodopentafluorobenzene).

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Oxidation von Acridinen und Azepinen in ihre 3-Oxoderivate mit Hilfe von hypervalenten aromatischen Jodverbindungen (Kurze Mitt.)

Zusammenfassung Die Acridine3,5 und6 sowie das Dibenzo[b,f]azepin4 wurden mit Hilfe der beiden hypervalenten Jod-Verbindungen Jodosobenzol (1) und Bis-trifluoroacetoxyiodbenzol (2) zu den entsprechenden 3-Acridinonen7,9 und10 sowie zum Dibenzoazepin-3-on8 oxidiert.

     

Promotion effect of hypervalent iodine compounds on the reactions of 3-hydroxy-4-nitrofurazan with cycloalkenes

Russian Chemical Bulletin -     

Direct lactone formation by using hypervalent iodine(III) reagents with KBr via selective C-H abstraction protocol

We have developed a new and reliable method for the direct construction of biologically important aryl lactones and phthalides from carboxylic and benzoic acids, using a combination of hypervalent iodine(III) reagents with KBr.     

1-substituted beta-carbolines by a Pictet-Spengler cyclization with thioortho esters and carbon-carbon bond formation via N-sulfonyl iminium ions generated from N,S-sulfonyl acetals

The reaction of N-tosyltryptamines with thioortho esters, leading to 1-thiosubstituted tetrahydro-beta-carbolines under modified Pictet-Spengler conditions, is described. The 1-heterosubstituted beta-carbolines furnished 1-substituted beta-carbolines upon reaction with Grignard reagents and silyl derivatives under Lewis acid promotion. [reaction: see text]     

Novel and direct oxidative cyanation reactions of heteroaromatic compounds mediated by a hypervalent iodine(III) reagent

The hypervalent iodine(III) reagent phenyliodine bis(trifluoroacetate) (PIFA) mediates the selective cyanation reactions of a wide range of electron-rich heteroaromatic compounds such as pyrroles, thiophenes, and indoles under mild conditions. These reactions proceed via a cation radical intermediate, and the key for the successful transformation presumably depends on the oxidation-reduction potential of the substrates used. The synthetic utility has been demonstrated through the conversion of these biologically important pyrroles 2f and 2g. [reaction: see text]     

The formation of medium-sized rings by the intramolecular cyclization of arylnitrenium ions

The synthesis of an aminodibenzo[a,c]octadiene and an aminodibenzo[a,c]octatriene, guided by molecular mechanics calculations, was effected by the intramolecular cyclization of the corresponding open chain nitrenium ions. Also reported is the predicted failure to synthesize another aminodibenzo[a,c]octadiene using this method.