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A simple protocol for the rapid synthesis of chalcogen-containing compounds by an I2O5-promoted oxidative Csp2–H selenation and seleno/thiocyanation of activated arenes is reported here.

A time-economical and robust synthesis of selenofunctionalized heterocycles by an I2O5-promoted selenylative heterocyclization of olefins with easily accessible diselenides is reported herein.

A photocatalytic strategy for the synthesis of γ-ketoesters was reported. Using DMSO as both the solvent and terminal oxidant, oxidative coupling of vinylarenes with bromocarboxylates proceeded readily, giving a variety of γ-ketoesters in good isolated yields and with a broad functional-group tolerance.

An environmentally friendly iodofunctionalization of olefins for the synthesis of various iodinated products was developed via the oxidative umpolung of iodide using I2O5 as the inorganic oxidant. ...

A three-component reaction of olefin, diselenide and water, alcohols, phenol, carboxylic acid, or amine by a commercially available hypervalent iodine(III) reagent, PhIO, was developed. This method provides access to a wide range of vicinally functionalized selenoderivatives under ambient conditions with mostly excellent yields and high diastereoselectivity. The developed reaction displays high levels of functional group compatibility and is suitable for the late-stage functionalization of styrene-functionalized biomolecules. Preliminary investigations on the mechanism of the reaction are also presented.

A metal-free cyclization of olefinic dicarbonyl compounds for the synthesis of various 5-halomethyl-4,5-dihydrofurans is presented. Using (diacetoxyiodo)benzene as the reaction promoter and halotrimethylsilane as the halogen source, the intramolecular haloenolcyclization of the 2-allyl-1,3-dicarbonyl compounds smoothly proceeded, leading to the corresponding 5-halomethyl-4,5-dihydrofurans in good to excellent isolated yields. Moreover, the resulting 5-iodomethyl products could be converted to functionalized furans in almost quantitative yields by treatment with DBU followed by acid-catalyzed rearrangement. The reactions could be carried out on a gram scale and did not require harsh reaction conditions. The good isolated yields, mild conditions, and operational simplicity make this reaction a viable method for the construction of different dihydrofuran and furan structures.

A metal-free cyclization of N-propargylamides for the synthesis of various oxazolines and oxazoles via a 5-exo-dig process is presented. Using (diacetoxyiodo)benzene (PIDA) as a reaction promoter and lithium iodide (LiI) as an iodine source, intramolecular iodooxygenation of N-propargylamides proceeded readily, leading to the corresponding (E)-5-iodomethylene-2-oxazolines in good to excellent isolated yields. In addition, using the PhI(OAc)2/LiI system, N-propargylamides can be converted to the corresponding oxazole-5-carbaldehydes in the presence of oxygen under visible light irradiation. The resulting products can be further converted into various oxazoline and oxazole derivatives after simple derivatizations, and this method ultimately offers an efficient route to a variety of biologically active structures.

A concise and efficient synthesis of (3R,3aS,6aR)-hexahydrofuro[2,3-b]furan-3-ol, a key building block for several clinical and experimental HIV protease inhibitors including the highly important drug darunavir, was achieved via a one-pot procedure using furan and Cbz-protected glycol aldehyde as starting materials. A [2+2]-photocycloaddition between both reactants which can be prepared from wood-based starting materials according to the principles of xylochemistry, followed by hydrogenation and lipase-catalyzed kinetic resolution afforded the target compound in high yield and up to 99% ee.

MnI2-catalyzed intramolecular iodoamination of unfunctionalized olefins was reported. Interaction of MnI2 with N-alkenyl amine/sulfonamide gave NRMnI which produced a CH2MnI intermediate via intramolecular aminometallation of C C double bond. Reductive elimination of CH2I from CH2MnI produced iodomethyl heterocycle with the release of Mn(0) which was confirmed by XPS and XRD experiments.

A concise and modular synthesis of phenanthroindolizidine alkaloids was achieved by combining iodoaminocylization with a free radical cyclization approach. The route described allowed the preparation of (±)-tylophorine, (±)-antofine, and (±)-deoxypergularinine in six steps. When commercially available l-prolinol was used as a chiral building block, (S)-(+)-tylophorine was also synthesized in 49% yield and >99% ee over five linear steps.

The catalytic activity of benzoic acid could be increased by introducing a hydrogen bond donor group at the ortho-position. Preliminary DFT calculation indicated that the activation of CC double bond was realized by the action of both the carboxyl group and the hydrogen bond donor. The amino group was brought to the activated CC bond by the interaction between the carboxyl oxygen and amino proton. This interaction also increased the nucleophilicity of the amino group. Thus, in the presence of 20 mol % of 2-(trifluoromethanesulfonamido)benzoic acid, intramolecular hydroamination of unfunctionalized olefins gave the corresponding products in up to 95% isolated yields.

A direct and catalyst-free method for the intramolecular aminoboration of unfunctionalized olefins is reported. In the presence of BCl3 (1 equiv) as the sole boron source, intramolecular aminoboration of sulfonamide derivatives of 4-penten-1-amines, 5-hexen-1-amines, and 2-allylanilines proceeded readily without the use of any catalyst. The boronic acids obtained after hydrolysis could be converted into the corresponding pinacol borates in a straightforward manner by treatment with pinacol under anhydrous conditions.

mCPBA-mediated metal-free intramolecular aminohydroxylation and dioxygenation reactions of unfunctionalized olefins are reported. In the presence of 1.2 equiv. of m-chlorobenzoic peracid, different N-sulfonyl 4-penten-1-amine substrates could be cyclized via epoxide intermediates, producing the corresponding 2-hydroxymethylpyrrolidine products in up to 92% yields. The reaction could be carried out at gram-scale, and the hydroxyl group could be further converted to a variety of different functional groups via conventional functional group transformation reactions. When N-sulfonyl carboxylimides were subjected to the same reaction, O-cyclization products oxolanimines were obtained. The skeletons of these compounds were confirmed using X-ray diffraction experiments.

BF3·Et2O was found to be effective for both intra- and intermolecular amination and oxygenation of unfunctionalized olefins. In the presence of 3 equiv. of BF3·Et2O, intramolecular hydroamination of N-(pent-4-enyl)-p-toluenesulfonamides, N-(hex-5-enyl)-p-toluenesulfonamides, intermolecular hydroamination between sulfonamides and cyclohexene, norbornene or styrene, lactonization of pent-4-enoic acid or hex-5-enoic acid compounds and esterification of cyclohexene with different carboxylic acids all proceeded readily, leading to the corresponding amination or oxygenation products in up to 99% isolated yields. Preliminary NMR experiments and DFT calculations suggested that the intramolecular hydroamination reactions proceeded via a sulfonimidic acid intermediate (NS–OH), and formation of the corresponding Bronsted acid HF or HBF4 was less likely.

A metal-free method for intramolecular halocyclization of unfunctionalized olefins was detailed. (Diacetoxyiodo)benzene (PIDA) was very effective for haloamidation, haloetherification, and halolactonization of unfunctionalized olefins. In the presence of 1.1 equiv of PIDA and suitable halogen sources, a variety of unfunctionalized olefins could be converted to the corresponding 1,2-bifunctional cyclic skeletons in good to excellent isolated yields, and key intermediates for biologically interesting compounds could be obtained in high yields under mild conditions via nucleophilic substitution of the thus obtained halocyclization products.

Trifluoroacetic acid was found to be effective in intramolecular hydroamination of unfunctionalized olefins bearing electron-rich amino groups, and the corresponding N-heterocycles were obtained in good isolated yields. The scope of the substrates was investigated, and a possible reaction mechanism was proposed. Substituents on C C double bonds and amino groups of the substrates showed drastic effects on the course of the reactions.

3-Chloropiperidine compounds were obtained via Cu(II)-promoted one-pot intramolecular chloroamination of N-benzyl-4-penten-1-amines and subsequent rearrangement. The reaction conditions leading to this skeleton were studied, and the structure of the product was confirmed by NMR as well as X-ray diffraction experiments.

A general and practical method for the preparation of trans-2-substituted-4-halopiperidines and cis-2-substituted-4-halotetrahydropyrans is reported. Using 5 mol % of AlCl3 as the catalyst and 2 equiv of trimethylsilyl halides as the halide sources, aza-Prins cyclization of N-tosyl homoallylamine or Prins cyclization of homoallylic alcohol with carbonyl compounds could be readily realized, giving the corresponding trans-2-substituted-4-halopiperidines or cis-2-substituted-4-halotetrahydropyrans in high yields and satisfactory diastereoselectivity.

Zinc halide-promoted hydroamination of 4-penten-1-amine compounds was studied. Preliminary results indicated that both steric and electronic factors are crucial for this Lewis acid-promoted reaction. ZnI2 gave the most promising results and the reactivity could be further increased upon addition of a suitable ligand. Up to 95% isolated yields were obtained when the reactions were carried out in 1,4-dioxane in the presence of 10 mol % of ZnI2 and 8-hydroxyquinoline.

A direct and catalyst-free method for the intramolecular aminoboration of unfunctionalized olefins is reported. In the presence of BCl3 (1 equiv) as the sole boron source, intramolecular aminoboration of sulfonamide derivatives of 4-penten-1-amines, 5-hexen-1-amines, and 2-allylanilines proceeded readily without the use of any catalyst. The boronic acids obtained after hydrolysis could be converted into the corresponding pinacol borates in a straightforward manner by treatment with pinacol under anhydrous conditions.

Aminohydroxylation product (IVb) can be carried out at gram-scale and the hydroxyl group can be further converted to a variety of different functional groups via conventional group transformation reactions such as azidation, bromination, acetylation, carboxylation and Swern oxidation.

A new method for the construction of oxazoline moiety was detailed. Using (diacetoxyiodo)benzene (PIDA) as the reaction promoter and halotrimethylsilane as the halogen source, intramolecular halooxygenation and halothionation of N-allylcarboxamides/N-allylcarbothioamides proceeded readily, leading to the corresponding 5-halomethyloxazolines/5-halomethylthiazolines in good to excellent isolated yields. The 5-halomethyl products could be converted to different derivatives via conventional nucleophilic substitution methods. The reactions were carried out using easily available starting materials, and did not need harsh reaction conditions. All these features made this reaction a viable method for the construction of different oxazoline and thiazoline structures.

A metal-free method for intramolecular halocyclization of unfunctionalized olefins was detailed. (Diacetoxyiodo)benzene (PIDA) was very effective for haloamidation, haloetherification, and halolactonization of unfunctionalized olefins. In the presence of 1.1 equiv of PIDA and suitable halogen sources, a variety of unfunctionalized olefins could be converted to the corresponding 1,2-bifunctional cyclic skeletons in good to excellent isolated yields, and key intermediates for biologically interesting compounds could be obtained in high yields under mild conditions via nucleophilic substitution of the thus obtained halocyclization products.

Intermolecular hydroamination of vinylarenes and anilines was studied using zinc triflate as catalyst. NMR experiments supported a Lewis acid activation of the C C double bond. Electronic/steric effect study indicated that Lewis acidity of the catalyst as well as the coordination property of the amine were the governing factors for successful hydroamination of the substrates. More nucleophilic amine would bind more tightly to the central metal, leading to an unproductive coordination. Approach of bulky amine to C C bond would be hindered, and an alternative electrophilic substitution on benzene ring of the amine would become the major reaction. Electrophilic substitution would become predominant when strong electron-donating group is presented on aniline benzene ring.

The CuCl2 promoted cyclization of unsaturated amines at room temperature leads to the formation of intermediate pyrrolidine derivatives, which rearrange at elevated temperature to produce piperidines.

The cooperative effect in organocatalytic hydroamination of unfunctionalized olefins was reported. In the presence of 3-hydroxy-2-naphthoic acid, N-benzyl 4-penten-1-amines and 5-hexen-1-amines produced the intramolecular cyclization products in good isolated yields.