Computationally Assisted Mechanistic Investigation into Hypervalent Iodine Catalysis: Cyclization of N-Allylbenzamide

Hypervalent iodine-mediated cyclization of bishomoallylamides to prolinols

A change in mechanism was observed in the hypervalent iodine-mediated cyclization of N-alkenylamides when the carbon chain between the alkene and the amide increased from two to three atoms. In the latter case, cyclization at the amide nitrogen to form the pyrrolidine ring was favored over cyclization at the amide oxygen. A DFT study was undertaken to rationalize the change in mechanism of this cyclization process. In addition, reaction conditions were developed, and the scope of this cyclization studied.

Toward a General Protocol for Catalytic Oxidative Transformations Using Electrochemically Generated Hypervalent Iodine Species

A simple catalytic electrosynthetic protocol for oxidative transformations mediated by hypervalent iodine reagents has been developed. In this protocol, electricity drives the iodine(I)/iodine(III) catalytic cycle enabling catalysis with in situ generated hypervalent iodine species, thereby eliminating chemical oxidants and the inevitable chemical waste associated with their mode of action. In addition, no added electrolytic salts are needed in this process. The developed method has been validated using two different hypervalent iodine-mediated transformations: (i) the oxidative cyclization of N-allylic and N-homoallylic amides to the corresponding dihydrooxazole and dihydro-1,3-oxazine derivatives, respectively, and (ii) the α-tosyloxylation of ketones. Both reactions proceeded smoothly under the developed catalytic electrosynthetic conditions without reoptimization, featuring a wide substrate scope and excellent functional group tolerance. In addition, scale-up to gram-scale and catalyst recovery were easily achieved maintaining the high efficiency of the process.

The PIFA-initiated oxidative cyclization of 2-(3-butenyl)quinazolin-4(3H)-ones - an efficient approach to 1-(hydroxymethyl)-2,3-dihydropyrrolo[1,2-a]quinazolin-5(1H)-ones

A regioselective method for the synthesis of 1-(hydroxymethyl)-2,3-dihydropyrrolo[1,2-a]quinazolin-5(1H)-ones - close structural analogs of naturally occurring vasicinone alkaloids - is described. The procedure is based on PIFA-initiated oxidative 5-exo-trig cyclization of 2-(3-butenyl)quinazolin-4(3Н)-ones, in turn prepared by thermal cyclocondensation of the corresponding 2-(pent-4-enamido)benzamides. The products obtained have a good natural product likeness (NPL) score and therefore can be useful for the design of natural product-like compound libraries.

The aryl iodine-catalyzed organic transformation via hypervalent iodine species generated in situ

The application of hypervalent iodine species generated in situ in organic transformations has emerged as a useful and powerful tool in organic synthesis, allowing for the construction of a series of bond formats via oxidative coupling. Among these transformations, the catalytic aryl iodide can be oxidized to hypervalent iodine species, which then undergoes oxidative reaction with the substrates and the aryl iodine regenerated again once the first cyclic cycle of the reaction is completed. This review aims to systematically summarize and discuss the main progress in the application of in situ-generated hypervalent iodine species, providing references and highlights for synthetic chemists who might be interested in this field of hypervalent iodine chemistry.

Organoiodine-Catalyzed Enantioselective Intramolecular Oxy­aminations of Alkenes with N-(Fluorosulfonyl)carbamate

Organoiodine-catalyzed enantioselective intramolecular oxyaminations were realized by the use of benzyl N-(fluorosulfonyl)carbamate as the exogenous nitrogen source. The method allows access to enantioenriched lactones and oxazolines, starting from γ,δ- and δ,ε-unsaturated esters and N-allyl amides, respectively.

Aminolactonization of Unactivated Alkenes Catalyzed by Aryl Iodine

A one-step protocol of the aryl iodine-catalyzed aminolactonization of unactivated alkenes under oxidation conditions was first reported to efficiently construct diverse amino lactones in a short time using HNTs₂ as the compatible nitrogen source. In addition, we investigated the influence of the reaction rate based on the structure of the iodoarene precatalyst, which revealed the selective adjustment effect on aminolactonization and oxylactonization. Finally, preliminary experiments verified the feasibility of asymmetric aminolactonization catalyzed by a chiral iodoarene precatalyst.

Recent discoveries on the structure of iodine(iii) reagents and their use in cross-nucleophile coupling

This perspective article discusses structural features of iodine(iii) compounds as a prelude to presenting their use as umpolung reagents, in particular as pertains to their ability to promote the selective coupling of two nucleophilic species via 2e^- oxidation.

Iodoarene-Catalyzed Oxyamination of Unactivated Alkenes to Synthesize 5-Imino-2-Tetrahydrofuranyl Methanamine Derivatives

Reported here is the room-temperature metal-free iodoarene-catalyzed oxyamination of unactivated alkenes. In this process, the alkenes are difunctionalized by the oxygen atom of the amide group and the nitrogen in an exogenous HNTs₂ molecule. This mild and open-air reaction provided an efficient synthesis to N-bistosyl-substituted 5-imino-2-tetrahydrofuranyl methanamine derivatives, which are important motifs in drug development and biological studies. Mechanistic study based on experiments and density functional theory calculations showed that this transformation proceeds via activation of the substrate alkene by an in situ generated cationic iodonium(III) intermediate, which is subsequently attacked by an oxygen atom (instead of nitrogen) of amides to form a five-membered ring intermediate. Finally, this intermediate undergoes an S_N2 reaction by NTs₂ as the nucleophile to give the oxygen and nitrogen difunctionalized 5-imino-2-tetrahydrofuranyl methanamine product. An asymmetric variant of the present alkene oxyamination using chiral iodoarenes as catalysts also gave promising results for some of the substrates.