Hypervalent iodine in the structure of N-heterocycles: synthesis, structure, and application in organic synthesis
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Hypervalent iodine in the structure of N-heterocycles: synthesis, structure, and application in organic synthesis Yulia А. Vlasenko1, Mekhman S. Yusubov1, Alexandr Shafir2*, Pavel S. Postnikov1* 1
Research School of Chemistry and Applied Biomedical Sciences, National Research Tomsk Polytechnic University, 30 Lenina Ave., Tomsk 634050, Russia; е-mail: [email protected] 2 Department of Biological Chemistry, IQAC-CSIC, 18–26 c/Jordi Girona, Barcelona 08034, Spain; e-mail: [email protected] Submitted April 16, 2020 Accepted April 21, 2020
Translated from Khimiya Geterotsiklicheskikh Soedinenii, 2020, 56(7), 854–866
The review is devoted to one of the most substantial trends in the chemistry of hypervalent iodine – synthesis, structure, and properties of heterocyclic and pseudoheterocyclic systems based on λ3- and λ5-iodanes. Among the variety of cyclic reagents based on hypervalent iodine, special attention has recently been paid to iodanes having close contact between I and N atoms. The review is addressing the synthetic approaches, structural features, and application of these reagents. The review includes more than 100 literature sources, mainly covering publications from 1990 to 2020 and key research from earlier years. Keywords: hypervalent iodine, organoiodine compounds, pseudoheterocyclic compounds, nitrogen–iodine bond, oxidation.
The chemistry of hypervalent iodine compounds (HIC) is one of the rapidly growing areas of organic synthesis.1 Reagents containing an iodine atom in high oxidation states are widely used as a source of electrophilic functional groups, mild and selective oxidants, as well as substrates for nucleophilic reactions by sp2- or sp3-hybridized carbon atom.2 Nowadays, HIC are widely applied in the thousands of organic transformations and attract the attention of researchers as affordable, cheap, and environmentally friendly reagents for organic synthesis. Several books and reviews have been devoted to various aspects of the reactivity of HIC.1 However, to date, the synthesis and application of pseudocyclic and cyclic λ3- and λ5-iodanes having in the structure a close contact between I and N atoms remains relatively poorly studied. This review is intended to summarize the achievements of chemical science in this area in recent years. The chemistry of HIC is associated primarily with the formation of strong bonds of the hypervalent iodine atom with electronegative atoms, represented primarily by oxygen and halogens.3 This ability is most clearly manifested in heterocyclic HIC, in which the heterocyclic 0009-3122/20/56(7)-0854©2020 Springer Science+Business Media, LLC
fragment is completed by formation of close contacts between oxygen and iodine atoms: such compounds are widespread among reagents based on HIC,4 both among λ3-iodanes 1–85–16 and among λ5-iodanes 9–1617–24 (Fig. 1). In turn, iodanes containing the N–I bond are much less common and are mainly represented by acyclic systems. For example, a large family of acyclic reagents (compounds 17–26)25–32 and salts containing an ionic bond
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