Recent Progress in Synthetic Applications of Hypervalent Iodine(III) Reagents

Hypervalent iodine(III) compounds have found wide application in modern organic chemistry as environmentally friendly reagents and catalysts. Hypervalent iodine reagents are commonly used in synthetically important halogenations, oxidations, aminations, heterocyclizations, and various oxidative functionalizations of organic substrates. Iodonium salts are important arylating reagents, while iodonium ylides and imides are excellent carbene and nitrene precursors. Various derivatives of benziodoxoles, such as azidobenziodoxoles, trifluoromethylbenziodoxoles, alkynylbenziodoxoles, and alkenylbenziodoxoles have found wide application as group transfer reagents in the presence of transition metal catalysts, under metal-free conditions, or using photocatalysts under photoirradiation conditions. Development of hypervalent iodine catalytic systems and discovery of highly enantioselective reactions using chiral hypervalent iodine compounds represent a particularly important recent achievement in the field of hypervalent iodine chemistry. Chemical transformations promoted by hypervalent iodine in many cases are unique and cannot be performed by using any other common, non-iodine-based reagent. This review covers literature published mainly in the last 7-8 years, between 2016 and 2024.

Phenyliodine(III)diacetate (PIDA): Applications in Organic Synthesis

One of the hypervalent iodines most widely used as an oxidizing agent in organic chemistry is (diacetoxyiodo)benzene (PhI(OAc)2), also known as (DAIB), phenyliodine(III) diacetate (PIDA). In this septennial mini-review, the authors have concisely and systematically presented representative applications of PIDA in organic synthesis involving C-H functionalization, hetero-hetero bond formations, heterocyclic ring construction, rearrangements or migrations and miscellaneous reactions along with their interesting mechanistic aspects starting from the summer of 2015 to the present.

Sterically crowded 1,4-diiodobenzene as a precursor to difunctional hypervalent iodine compounds

A bulky 1,4-di-iodobenzene having four adjacent para-^tBu-C₆H₄ group (Ar') substituents (1) was used to prepare the di-hypervalent iodine compound 1,4-[I(OAc)₂]₂-2,3,5,6-Ar'₄-C₆ (2). Despite the steric encumbrance of the iodine center by the flanking aryl substituents, compound 2 undergoes ready cyclization under mild conditions (excess CF₃COOH at 55 °C, 30 min) to afford a dicyclic di-iodonium di-triflate salt 3. The single crystal structures of compounds 2 and 3 were examined and compared to the formerly characterized precursor 1. The para-tert-butyl groups on these compounds also render the compounds more soluble than multifunctional hypervalent iodine (HVI) compounds. HVI compounds having multiple iodine(III) centers are increasingly of interest for applications as recyclable reagents, materials precursors, and as Lewis acids.

Safer Synthesis of (Diacetoxyiodo)arenes Using Sodium Hypochlorite Pentahydrate

A practical method for the preparation of (diacetoxyiodo)arene ArI(OAc)₂ is described. The use of commercially available sodium hypochlorite pentahydrate (NaClO·5H₂O) enabled safe, rapid, and inexpensive oxidation of iodoarenes with electron-withdrawing and -donating substituents. The method allows tandem divergent access to synthetically useful organo-λ³-iodanes such as hydroxyl(tosyloxy)iodobenzene, iodosylbenzene, iodonium ylide, etc.