The Synthesis of Heterocyclic Compounds with Hypervalent Organoiodine Reagents

Preparation of a benziodazole-type iodine(III) compound and its application as a nitrating reagent for synthesis of furazans via a copper-catalyzed cascade process

The existing hypervalent I(III) reagents bearing ONO2 group are limited in types and their applications primarily focused on the nitrooxylation reactions featuring a fully-exo fashion. Herein, a benziodazole-type O2NO-I(III) compound was prepared and its reaction with β-monosubstituted enamines in the presence of CuI could trigger a radical nitration/cyclization/dehydration cascade to provide a series of less explored but biologically interesting furazan heterocycles. Mechanistically, the benziodazole-type O2NO-I(III) compound acts as a nitrating reagent and incorporates its NO moiety into the final furazan product in a fully-endo model, a process of which was proposed to involve nitration, cyclization and dehydration.

Advances in Synthetic Applications of Hypervalent Iodine Compounds

The preparation, structure, and chemistry of hypervalent iodine compounds are reviewed with emphasis on their synthetic application. Compounds of iodine possess reactivity similar to that of transition metals, but have the advantage of environmental sustainability and efficient utilization of natural resources. These compounds are widely used in organic synthesis as selective oxidants and environmentally friendly reagents. Synthetic uses of hypervalent iodine reagents in halogenation reactions, various oxidations, rearrangements, aminations, C-C bond-forming reactions, and transition metal-catalyzed reactions are summarized and discussed. Recent discovery of hypervalent catalytic systems and recyclable reagents, and the development of new enantioselective reactions using chiral hypervalent iodine compounds represent a particularly important achievement in the field of hypervalent iodine chemistry. One of the goals of this Review is to attract the attention of the scientific community as to the benefits of using hypervalent iodine compounds as an environmentally sustainable alternative to heavy metals.

Synthesis of 5-aryl-3-C-glycosyl- and unsymmetrical 3,5-diaryl-1,2,4-triazoles from alkylidene-amidrazones

A general synthetic method was elaborated for 3,5-disubstituted-1,2,4-triazoles with different groups in positions 3 and 5.

Organoiodine(iii) mediated intramolecular oxidative cyclization of 1-(3-arylisoquinolin-1-yl)-2-(arylmethylene)hydrazines to 5-aryl-3-(aryl)-[1,2,4]triazolo[3,4-a] isoquinolines

Intramolecular C–N bond formation is achieved through oxidative cyclization of 1-(3-arylisoquinolin-1-yl)-2-(arylmethylene)hydrazines, 3, in the presence of hypervalent iodine oxidant and dichloromethane at ambient temperature.

Preparation, structure, and versatile reactivity of pseudocyclic benziodoxole triflate, new hypervalent iodine reagent

New, highly electrophilic hypervalent iodine reagent, triflate derivative of benziodoxole, was prepared and structurally characterized.

Iodine(III)-mediated tandem oxidative cyclization for construction of 2-nitrobenzo[b]furans

Various 3-alkyl-2-nitrobenzo[b]furans were synthesized from common intermediate 2-(2-nitroethyl)phenols via a hypervalent iodine-induced oxidative cyclization, with good to excellent yields. This facile route is able to efficiently functionalize 2-nitrobenzo[b]furans, which are difficult to obtain by classical methods.

Synthesis and fluorescence studies of porphyrin appended 1,3,4-oxadiazoles

A modular synthetic approach for preparing a family of porphyrin appended 1,3,4-oxadiazoles 9 is described. The porphyrin hydrazides are reacted with aryl aldehydes in presence of Yb(OTf)3 as catalyst to give porphyrin hydrazones 8 which are then cyclized to porphyrin appended 1,3,4-oxadiazoles 9 using iodobenzene diacetate. Photophysical studies in CHCl3 solvent shows that the electronic structure of the porphyrin chromophore is not greatly perturbed by the incorporation of the oxadiazole group onto the meso-phenyl ring. Efficient quenching of porphyrin fluorescence was observed in 9g with a pyridinium moiety.

Hofmann rearrangement of carboxamides mediated by hypervalent iodine species generated in situ from iodobenzene and oxone: reaction scope and limitations

Alkylcarboxamides can be converted to the respective amines by Hofmann rearrangement using hypervalent iodine species generated in situ from PhI and Oxone in aqueous acetonitrile. On the basis of this reaction, a convenient experimental procedure for the preparation of alkylcarbamates using Oxone as the oxidant in the presence of iodobenzene in methanol has been developed. An efficient method for direct conversion of substituted benzamides to the respective quinone derivatives by treatment with Oxone and iodobenzene in aqueous acetonitrile has also been found.

Organoiodine(V) reagents in organic synthesis

Organohypervalent iodine reagents have attracted significant recent interest as versatile and environmentally benign oxidants with numerous applications in organic synthesis. This Perspective summarizes synthetic applications of hypervalent iodine(V) reagents: 2-iodoxybenzoic acid (IBX), Dess-Martin periodinane (DMP), pseudocyclic iodylarenes, and their recyclable polymer-supported analogues. Recent advances in the development of new catalytic systems based on the generation of hypervalent iodine species in situ are also overviewed.

A general and convenient preparation of [bis(trifluoroacetoxy)iodo]perfluoroalkanes and [bis(trifluoroacetoxy)iodo]arenes by oxidation of organic iodides using oxone and trifluoroacetic acid

[Bis(trifluoroacetoxy)iodo]perfluoroalkanes C(n)F(2n+1)I(OCOCF(3))(2) (n = 4, 6, 8, 10, 12) can be conveniently prepared by the oxidation of the corresponding perfluoroalkyl iodides with Oxone in trifluoroacetic acid at room temperature and subsequently converted to the stable [hydroxy(tosyloxy)iodo]perfluoroalkanes, C(n)F(2n+1)I(OH)OTs, by treatment with p-toluenesulfonic acid. This general and convenient procedure has been further extended to the synthesis of various [bis(trifluoroacetoxy)iodo]arenes, ArI(OCOCF(3))(2).

Hypervalent iodine reagents as a new entrance to organocatalysts

The catalytic utilization of hypervalent iodine reagents, largely in consideration of economical and environmental viewpoints, is a most attractive strategy due to their unique features as extremely useful oxidants, with mild, safe, and environmentally friendly characteristics. In addition to a system based on electrochemical reoxidation conditions, new reliable catalytic methods have emerged in recent years that can broaden the scope of the catalytic concept. For these contributions, a catalytic strategy is now available for performing many representative types of oxidative bond-forming reactions and alcohol oxidations mediated by hypervalent iodines, some of which even include key transformations for natural product synthesis. A suitable choice of terminal oxidants, e.g., m-chloroperbenzoic acid (mCPBA) or Oxone, for generation of active hypervalent iodine(iii) or (v) species from iodoarenes in situ, has led to recent rapid expansion in this field. This feature article highlights the historical background and the efforts made to realize the catalytic utilization of these reagents, especially with focus on iodine(iii).