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Previously, we developed a gold-catalyzed cycloisomerization of dienediynes to synthesize the fused 6,7,5-tricyclic compounds. This reaction involves aliphatic C-H functionalization under mild conditions with high regio- and diastereoselectivities. Herein, we present a combined density functional theory (DFT) and experimental study to understand its mechanism. The reaction starts with a 6-endo-dig cyclization to generate a cis-1-alkynyl-2-alkenylcyclopropane. Then, a Cope rearrangement takes place to give a seven-membered-ring allene intermediate, whose central carbon atom possesses vinyl cation character and thus is highly reactive toward aliphatic C-H insertion. After the C-H insertion, two successive [1,2]-hydride shifts then occur to give the tricyclic product and to complete the catalytic cycle. Notably, steric effect induced by the bulky ligand is found to be important for the diastereocontrol in the C-H insertion step. DFT calculations suggested that the malonate-tethered substrate utilized in our previous work may undergo an undesired 5-exo-dig cyclization under gold catalysis, which could be the reason why the desired fused 6,7,5-tricarbocyclic product was not generated. These mechanistic insights then guided us to design substrates with a shortened carbon tether in the present work to inhibit the exo-dig cyclization so that the tandem cyclopropanation/Cope rearrangement/C-H functionalization could occur to construct polycarbocycles containing a seven-membered ring. This prediction was supported by new experiments, providing a new strategy to access fused 5,7,5-tricyclic and 5,7,6,6-tetracyclic carbocycles. In addition, how the substituents affect the chemoselectivity was also investigated.

A silver-catalyzed nitration/annulation of α-alkynyl arylols is reported by using tert-butyl nitrite (TBN) as a NO2 radical precursor, from which a set of 3-nitrated benzofurans were synthesized with moderate to good yields. This transformation initiated by an in situ generated NO2 radical proceeds efficiently under mild and neutral redox conditions, which provides a new pathway toward the 3-nitrobenzofuran framework via catalytic difunctionalization of internal alkynes.

Two neodymium β-diketonates metal-organic complexes, Nd(TTA)3TPTZ (1) and Nd(BFA)3TPTZ (2), have been synthesized by using two β-diketone ligands 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione (HTTA) and 4,4,4-trifluoro-1-phenyl-1,3-butanedione (HFBA), and a macrocyclic conjugate ligand, 2,4,6-tri(2-pyridyl)-1,3,5-triazine (TPTZ). The crystal structures of these two complexes were determined by single crystal X-ray diffraction. The X-ray diffraction analysis showed that each neodymium ion in the two complexes formed a Nine-Coordinated structure with six oxygen atoms of HTTA (or HBFA) ligands and three nitrogen atoms of TPTZ ligand by the characteristic of triclinic with P 1 ( — ) space group both. In the crystal structure of the two complexes, a very obvious aromatic donor-acceptor interaction can be observed between adjacent TPTZ ligand molecules, which play an important role in the formation of three-dimensional structures. The complexes were also characterized by infrared spectroscopy, elemental analysis, thermogravimetric and fluorescence spectra. Fluorescence analysis showed that the two complexes exhibited characteristic neodymium-centered emission due to the significant antenna effect of these ligands.

Summary Herein, we describe the protecting-group-free total synthesis of two structurally diverse Isodon diterpenoids, (+)-ent-kauradienone (3) and (−)-jungermannenone C (4), in 12 and 14 steps respectively, through sequential applications of three radical-based reactions, including the photoinduced skeletal rearrangements of bicyclo[3.2.1]octene ring systems. Further investigations of this photochemical radical rearrangement on a series of diverse terpenoids demonstrated both the unparalleled functional-group tolerance and the broad applicability of such late-stage photochemical rearrangements for the synthesis of structurally diverse and complex small molecules. Overall, the mild nature of late-stage photoinduced skeletal rearrangements might suggest that they are possible in a biological setting in unappreciated complimentary biosynthetic pathways.

Two new types of silver-catalyzed nitration–annulations of 2-alkynylanilines with tert-butyl nitrite (TBN) were reported, leading to the selective formation of a variety of nitrated indoles and indazole-2-oxides by changing the N-protection of 2-alkynylanilines. Ag-Catalyzed nitration–annulation of N-sulfonyl 2-alkynylanilines without C4 substituents afforded 5-nitroindoles under neutral-redox conditions, whereas the presence of C5 substituents gave 7-nitroindoles through silver catalysis. N-Methyl 2-alkynylanilines underwent a completely different process to furnish aroyl indazole-2-oxides.

A new Cu(II)-catalyzed annulation–cyanotrifluoromethylation of 1,6-enynes with Togni's reagent and trimethylsilyl cyanide (TMSCN) has been established, enabling the direct construction of trifluoromethylated 1-indanones with an all-carbon quaternary center in good yields. This reaction was performed by using low-cost Cu(OTf)2 as the catalyst and Togni's reagent as both the radical initiator and a CF3 source, providing an efficient protocol for building up an 1-indanone framework with wide functional group compatibility. The reaction mechanism was proposed through a radical triggered addition/5-exo-dig cyclization/oxidation/nucleophilic cascade.

Two neodymium(III) fluorou ternary complexes, [Nd(C5H2F6O2)3(C18H15OP)2] (C5H2F6O2 = hexafluoroacetylacetone, C18H15OP = triphenylphosphine oxide) (1) and [Nd(C5H2F6O2)3(C12H24N3O4P)2] (C5H2F6O2 = hexafluoroacetylacetone, C12H24N3O4P) = tri(4-morphollno) phosphine oxide) (2) have been synthesized by mild condition. The single crystals suitable for X-ray measurement were obtained and the structures of the two complexes were determined by X-ray diffraction in solid states. Single crystal analysis revealed that the two complexes were both eight-coordinated with one central Nd ion and eight O atoms from ligands. They were crystallized in monoclinic symmetry with P21/c and monoclinic symmetry C2/c space group, respectively. The complexes were characterized by IR-spectroscopy, thermogravimetric, elemental analyses and fluorescent. In fluorescence spectra, the two complexes both exhibit characteristic neodymium-centered emission.

A new sulfenylation reaction has been established, stereoselectively affording 37 examples of α-arylthio-α,β-unsaturated ketones with generally good yields via a metal-free three-component reaction of α-thiocyanate ketones with diaryliodonium salts and 1,2-dicarbonyls. The reaction enabled multiple bond-forming events including C(sp2)–S formation to provide a high-efficient and practical method toward α-arylthio-α,β-unsaturated ketones. The reasonable mechanism for forming α-arylthio-α,β-unsaturated ketones was proposed.

Catalytic inverse electron demand Diels-Alder (IEDDA) reactions of heterocyclic aza-dienes are rarely reported since highly reactive and electron-rich dienophiles are often found not compatible with strong acids such as Lewis acids. Herein, we disclose that TFA-catalyzed reactions of electron-deficient 1,3,5-triazines and electron-deficient aldehydes/ketones can take place. These reactions led to highly functionalized pyrimidines as products in fair to good yields. The reaction mechanism was carefully studied by the combination of experimental and computational studies. The reactions involve a cascade of stepwise inverse electron demand hetero-Diels-Alder (ihDA) reactions, followed by retro-Diels-Alder (rDA) reactions and elimination of water. An acid was required for both ihDA and rDA reactions. This mechanism was further verified by comparing the relative reactivity of aldehydes/ketones and their corresponding vinyl ethers in the current reaction system.

A new silver-mediated 5-exo-dig cyclization of 2-alkynylbenzonitriles with disubstituted phosphine oxide and H2O has been developed. The reaction enables multiple bond-forming events including C–P, C–C and C–O bonds under atmospheric conditions, leading to the concise and direct formation of 28 examples of phosphorus-containing 1-indenones with generally good yields.

A chiral phosphoric acid-catalyzed Friedel–Crafts alkylation of o -hydroxybenzyl alcohols with 3-alkylindoles has been established, which was used to construct a biologically important diarylindol-2-ylmethane scaffold in high yields and with good enantioselectivities (up to 99% yield, 90:10 er ). Moreover, these novel compounds were subjected to tests to determine the in vitro cytotoxicity against carcinoma Hela cells. Nearly all of the tested compounds exhibited strong or moderate cytotoxicity to Hela cells with IC 50 values ranging from 6.821 to 28.042 μg/mL.

A new sulfinate salt-mediated radical relay for the completion of C(sp3 )-H bond indenylation of cyclic ethers with readily available 2-alkynylbenzonitriles by combining silver/tert-butyl peroxide (TBHP) was established, providing a wide range of 3-alkylated 1-indenones with generally good yields. Interestingly, the current reaction system can tolerate an S-centered radical and a C-centered radical in one pot, in which the S-centered radical promotes the formation of the C-centered radical to induce a radical cascade without disturbing the reaction process. A reaction mechanism is also proposed based on control experiments.

Herein, we report a novel strategy based on a conformationally controlled RCM by a removable silyl group, which allows the facile synthesis of various bicyclo[n.3.1]alkenes, especially a set of highly strained bicyclo[5.3.1]alkenes. Further derivatizations of the silyl group and the resultant double bond of bicyclo[5.3.1]undecene 2 f enabled a concise synthesis of A-B-C ring skeleton of taxol. Density functional theory (DFT) calculations suggest that the introduction of a bulky silyl group at C-5 position of the 1,3-dialkenylcyclohexanol substrates dramatically lowers the energy bias gap between diaxial conformers (to RCM) and diequatorial conformers (to cross metathesis), thereby favoring the expected RCM reaction to give the challenging bridged molecules.

Intramolecular proton transfers are important processes in chemical reactions and biological transformations. In particular, the translocation of reactive carbanion centers can be achieved through 1,n-proton transfer in either a direct or an assisted manner (via the protonation/deprotonation mechanism). Despite some mechanistic investigations on proton transfers within zwitterionic species, no guiding principles have been summarized for carbanion-induced intramolecular proton transfers. Herein, we report our quantum chemical study on the carbanion translocations via intramolecular proton transfers. Our calculations indicated that the reaction barriers generally decrease with longer tether lengths and more π-withdrawing substituents. The physical bases behind these effects were revealed according to the charge and bond energy decomposition analysis, showing that the destabilizing closed-shell Pauli repulsions play important roles in determining the relative ease of intramolecular proton transfers. We also found that the thermodynamic driving force may affect the regiochemistry. This study may help chemists to understand whether a carbanion translocation occurs via an intramolecular proton transfer or with the assistance of proton shuttles, such as water and alcohols.

Reported is the first scalable synthesis of rac-jungermannenones B and C starting from the commercially available and inexpensive geraniol in 10 and 9 steps, respectively. The unique jungermannenone framework is rapidly assembled by an unprecedented regioselective 1,6-dienyne reductive cyclization reaction which proceeds through a vinyl radical cyclization/allylic radical isomerization mechanism. DFT calculations explain the high regioselectivity observed in the 1,6-dienyne reductive radical cyclization.