N-Trifluoropropylation of Azoles through N-Vinylation and Sequential Hydrogenation

Al(OTf)3-Catalyzed Regioselective N2-Arylation of Tetrazoles with Diazo Compounds

Regioselective methods to access alkylated tetrazoles still remain a challenging goal. Herein, we describe a novel regioselective protocol for N2-arylation of tetrazoles with diazo compounds using inexpensive Al(OTf)3. This reaction could be conducted under mild conditions to access a diverse array of alkylated tetrazoles with 2-substituted tetrazoles as the major products, demonstrating a comprehensive range of substrate compatibility and excellent functional group compatibility. Mechanistic studies revealed a carbene-free process in this reaction procedure. Furthermore, the scale-up reaction and transformations of the N2-arylation of tetrazole products demonstrated the potential of this strategy.

Reactivity of α-diazo sulfonium salts: rhodium-catalysed ring expansion of indenes to naphthalenes

In the presence of catalytic amounts of the paddlewheel dirhodium complex Rh2(esp)2, α-diazo dibenzothiophenium salts generate highly electrophilic Rh-coordinated carbenes, which evolve differently depending on their substitution pattern. Keto-moieties directly attached to the azomethinic carbon promote carbene insertion into one of the adjacent C-S bonds, giving rise to highly electrophilic dibenzothiopyrilium salts. This intramolecular pathway is not operative when the carbene carbon bears ester or trifluoromethyl substituents; in fact, these species react with olefins delivering easy to handle cyclopropyl-substituted sulfonium salts. When indenes are the olefins of choice, the initially formed cyclopropyl rings smoothly open with concomitant departure of dibenzothiophene, enabling access to a series of 2-functionalized naphthalenes.

Three-component N-alkenylation of azoles with alkynes and iodine(III) electrophile: synthesis of multisubstituted N-vinylazoles

A stereoselective N-alkenylation of azoles with alkynes and iodine(III) electrophile is reported. The reaction between various azoles and internal alkynes is mediated by benziodoxole triflate as the electrophile in a trans-fashion, affording azole-bearing vinylbenziodoxoles in moderate to good yields. The tolerable azole nuclei include pyrazole, indazole, 1,2,3-triazole, benzotriazole, and tetrazole. The iodanyl group in the product can be leveraged as a versatile synthetic handle, allowing for the preparation of hitherto inaccessible types of densely functionalized N-vinylazoles.

Fluorinated Vinyl Sulfonium Salts and Their Synthetic Utilization

The fluorinated building block strategy and the direct fluorination strategy are of great importance for the synthesis of new fluorinated molecules. These strategies complement each other and can be combined to develop a new methodology for the construction of a wide variety of fascinating organofluorine compounds. In our opinion, the versatile building blocks used in this method should satisfy the following conditions: 1) readily prepared from commercially available reagents; 2) easy to handle; 3) storage under ordinary conditions without noticeable decomposition; 4) wide applicability. Based on the aforementioned requirements, we focused on the use of vinyl sulfonium salts. This brief review describes the synthesis of five types of fluorinated vinyl sulfonium salts and their reactions. Especially, we featured typical fluorinated groups containing trifluoromethyl (CF3 ), difluoromethyl (CF2 H), monofluoromethyl (CFH2 ), monofluoro (F) or β-bromotetrafluoroethyl (BrCF2 CF2 ) moieties in combination with vinyl sulfonium salts.

Regio- and Stereoselective Switchable Synthesis of (E)- and (Z)-N-Carbonylvinylated Pyrazoles

Regio- and stereoselective switchable synthesis of (E)- and (Z)-N-carbonylvinylated pyrazoles is first developed by using the Michael addition reaction of pyrazoles and conjugated carbonyl alkynes. Ag₂CO₃ plays a key role in the switchable synthesis of (E)- and (Z)-N-carbonylvinylated pyrazoles. Ag₂CO₃-free reactions lead to thermodynamically stable (E)-N-carbonylvinylated pyrazoles in excellent yields whereas reactions with Ag₂CO₃ give (Z)-N-carbonylvinylated pyrazoles in good yields. It is noteworthy that (E)- or (Z)-N¹-carbonylvinylated pyrazoles are obtained with high regioselectivity when asymmetrically substituted pyrazoles react with conjugated carbonyl alkynes. The method can also extend to the gram scale. A plausible mechanism is proposed on the basis of the detailed studies, wherein Ag⁺ acts as coordination guidance.

Synthesis of CF3-Substituted Alkylamines, 1,2-Bisazoles, and 1,4,5,6-Tetrahydro-1,2,4-triazines from Newly Designed Tetrazole-Activated Trifluoromethyl Alkenes

A new class of Michael acceptor, tetrazolyl-trifluoromethyl alkenes, has been discovered. They readily undergo Michael-type addition instead of addition-elimination reaction with aliphatic amines and azoles to furnish β-trifluoromethyl alkylamines and CF₃-substituted 1,2-bisazole derivatives, respectively. Additionally, some of the products are capable of engaging in microwave-assisted intramolecular denitrogenative annulation, leading to the formation of CF₃-substituted 1,4,5,6-tetrahydro-1,2,4-triazines that are otherwise difficult to access by other methodologies.