A transition metal-free and hypervalent iodine-promoted annulative aminocyanation of unactivated alkenes has been developed for the first time. This regioselective 5-exo-trig process provides a concise method to synthesize diversely substituted cyanated pyrrolidine, piperidine and indoline derivatives under mild reaction conditions with up to 80% yield, in which the cyanated position of the double bond is controlled by different hypervalent iodine regents.

π-Conjugated boron complexes have been considered as excellent fluorescent dye system and utilized in various fields, such as organic electronics, photonics, nanoemitters and dyestuff industry. In this paper, we developed a fluoroboron coordination by employing in situ generated BF3·H2O as fluoroboron souce and afforded a series of novel species of N,O π-conjugated boron complexes. Moreover, we achieved the Suzuki cross-coupling reaction of iodo-substituted complex with different boronic acids to further expand the structural diversity of N,O π-conjugated fluoroboron complexes.

A BF3·OEt2-promoted direct substitution of various alcohols with sodium sulfinates affording sulfinates under mild conditions has been developed. Further reaction of the hydroxysteroids achieves the highly complex sulfinates in good yields, which are two potential pharmacophores routinely encountered in drug discovery.

We have developed a one-pot iron-catalysed sequential reaction of secondary amines with primary alcohols, trimethylsilyl cyanide and TBHP under mild reaction conditions to give the corresponding α-aminonitriles.

Hypervalent iodine (III)-intermediated direct oxidative rearrangement of 3-hydroxybut-2-enimidates affording oxazoles under mild conditions has been developed. This protocol provides a new methodology to the synthesis of compounds containing oxazole structure.

A novel ether/BF3 reductive system has been described, in which diphenylmethanols and their ether and ester derivatives are used as starting materials. Reductions are performed in ether under reflux and an argon atmosphere, and the addition of extra water is beneficial to this reduction. A series of alkanes are able to be prepared with good to excellent yields. A deuterated experiment exhibits that the reductive hydrogen is generated from ether. The mechanism is discussed in detail to explain the observed reactivity.

An environmentally benign and metal-free cyanation method of tertiary amines oxidated by hypervalent iodine(III) intermediate generated in situ from PIFA (or DIB) and TMSCN has been developed. A variety of substituent groups on amines are tolerated to the oxidation of α-C–H bond to form C–C bond in the absence of metal catalysts with yields of up to 74%.

A Beckmann-type rearrangement of o-hydroxy and o-aminoaryl N–H ketimines has been developed to prepare benzoxazoles and N-Ts benzimidazoles, respectively. The ketimine derivatives were easily prepared by condensation of ammonia with the corresponding ketones and (diacetoxyiodo)benzene was found to act as an efficient oxidant to trigger the [1,2]-aryl migration towards the formation of the desired heterocycles. Depending on the substitution pattern, the results revealed another mechanistic pathway through which benzisoxazoles or 1H-indazoles could be formed. The Beckmann-type rearrangement strategy was applied to the synthesis of benzimidazole-containing biorelevant targets such as chlormidazole and clemizole.

The iron(III)-promoted free radical oxidation of anilines has been further developed. Anilines including those bearing strong electron-withdrawing groups on benzene ring were readily converted into corresponding self-coupling benzidines. With addition of base, the methyl on nitrogen was activated and the free radical oxidations tended to furnish the corresponding self-bridged assembling diaminodiarylmethanes.

To examine the assembly methodology of diarylmethanes, a benzylation of (hetero)arenes with benzyl halides has been developed and various diarylmethanes were furnished with yields of up to 98% and regioselectivities of up to >99%. The complexation of the by-product halogen hydride with BF3·OEt2 generated the Bronsted acid BF3·HX (HBF3X, X=Cl or Br) in situ to synergistically promote the benzylation.

An efficient method to synthesize β-ketonitriles from silyl enol ethers by an umploung hypervalent iodine(III)–CN species generated in situ from PhIO/BF3·Et2O/TMSCN has been developed for the first time. This method can be applied to structurally diverse aromatic and aliphatic substrates and further extended to preparation of bioactive compounds like 5-aminopyrazole and 5-aminoisoxazole.

An efficient and environmentally friendly benzylation of arenes with benzyl ethers as benzyl donors using BF3–Et2O to generate in situ the superacid BF3–H2O as an efficient promotor has been described. A wide variety of functional groups have been investigated and found to be compatible to give the desired diarylmethanes in yields of up to 99%. The crucial role of the moisture content in this transformation has been demonstrated by detailed investigations.

A convenient procedure employing simple starting materials benzyl alcohols and acetates as the benzyl donors to assemble a series of diarylalkanes through benzylation of arenes using in situ prepared superacid BF3–H2O as an efficient promoter has been developed. The beneficial role of water in the reaction has been clarified with combination of control experiments and 11B NMR analysis. This reaction is a self-promoted model, which is triggered by the trace of water and continuously promoted by self released by-product water (or carboxylic acid). A wide range of substrates are investigated and the moderate to excellent yields and the good regioselectivities for secondary benzyl alcohols as well as arenes bearing electron-withdrawing groups have been achieved. As a result, moisture in the reaction system has been utilized as an efficient initiator in all benzylation cases.

Under open-flask conditions, an efficient method to assemble a series of diversely functionalized diarylketones in the presence of commercially available NBS has been developed. Yields of up to 99% have been achieved employing diarylmethanes as starting material. Based on 18O-labeled experiment, the addition of stoichiometric water eventually leads to excellent yields in all carbonylation cases.

Under neat conditions, an efficient method for synthesis of imidoesters has been developed using cyanatobenzenes and dicarbonyl compounds. Nucleophilic addition spontaneously occurred between the two kinds of materials at room temperature with yields of up to 90%. A mechanism directed towards to the imidoester formation has been proposed.An efficient method for synthesis of imidoesters has been developed using cyanatobenzenes reagents and dicarbonyl compounds, and yields of up to 90% have been obtained under neat conditions.Figure optionsDownload full-size imageDownload as PowerPoint slide

Practical BF3·Et2O catalyzed reactions between indoles and a series of carbonyl compounds at room temperature are described, which afford bis(indolyl)methanes with isolated yields up to 96%.Practical BF3·Et2O catalyzed reactions between indoles and a series of carbonyl compounds at room temperature are described, which afford bis(indolyl)methanes with isolated yields up to 96%.

An effective approach for the direct benzylhalogenation with in situ generation of hypervalent halides has been developed. A variety of benzyl halides are produced in moderate to excellent yields (up to 99%) with high regioselectivities. UV absorption spectrum is employed to detect the formation of tert-butyl hypoiodite.Effective benzylhalogenation triggered by in situ prepared hypervalent halide.

Under open-flask conditions in the presence of commercially available FeCl3·6H2O, N,N-disubstituted anilines can be converted into diversely functionalized benzidines with yields of up to 99%. Oxidative coupling was extended to N-monosubstituted anilines, and the method was applied to the efficient preparation of 6,6′-biquinoline. Mechanistic investigations have also been performed to explain the observed reactivities.

Reactions of lithium halide (LiX, X = F, Cl, Br and I) and methyl halide (CH3X, X = F, Cl, Br and I) have been investigated at the B3LYP/6-31G(d) level of theory using the microhydration model. Beginning with hydrated lithium ion, four or two water molecules have been conveniently introduced to these aqueous-phase halogen-exchange SN2 reactions. These water molecules coordinated with the center metal lithium ion, and also interacted with entering and leaving halogen anion via hydrogen bond in complexes and transition state, which to some extent compensated hydration of halogen anion. At 298 K the reaction profiles all involve central barriers ΔEcent which are found to decrease in the order F > Cl > Br > I. The same trend is also found for the overall barriers (ΔEovr) of the title reaction. In the SN2 reaction of sodium iodide and methyl iodide, the activation energy agrees well with the aqueous conductometric investigation.

We have developed a one-pot iron-catalysed sequential reaction of secondary amines with primary alcohols, trimethylsilyl cyanide and TBHP under mild reaction conditions to give the corresponding α-aminonitriles.